Lay Summaries Archive

Read Lay Summaries from previous volumes of Functional Ecology here:

Early View Lay Summaries

 

Mothers increase yolk oestrogen levels and the production of female offspring across the nesting season

Amanda W. Carter, Rachel M. Bowden, Ryan T. Paitz Mothers increase yolk oestrogen levels and the production of female offspring across the nesting season .

Moms can permanently affect the phenotype of their offspring through a variety of causes termed “maternal effects,” (e.g., health during gestation affecting offspring growth rates, or the amount of care provided to young after birth impacting offspring stress). Maternal effects can help match the phenotype of the offspring to the offspring’s environment to enhance fitness, but sometimes the phenotype that is most advantageous differs between sons and daughters. Therefore, conditions that enable females to either directly manipulate the sex of their offspring or match maternal effects to a predictable pattern of sex ratio variation would be advantageous.

We investigated the ability of red-eared slider turtles to match maternal effects to offspring sex. Turtles are a great system for investigating sex-specific maternal effects because females transfer steroids to the eggs which may affect hatchling phenotype, including sex. In our species, females deposit higher concentrations of oestrogens in late season eggs, compared to early season eggs, which could result in a seasonal sex ratio shift. Also, in many turtles, incubation temperatures determine whether offspring develop as male or female. Turtle nest temperatures fluctuate daily, however, and we don’t know how even slight increases in fluctuating temperatures, as would occur across the nesting season, affect sex determination.

We collected turtle eggs early and late in the nesting season and incubated them under fluctuating incubation temperatures. We found that late season eggs, which contain higher concentrations of maternally derived oestrogens, are more likely to produce female hatchlings than early season eggs. Combined with even a slight increase in incubation temperature (0.5°C), late season eggs produce up to 49% more female hatchlings than early season eggs.

These findings demonstrate a seasonal shift in sex ratios driven by maternal effects and subtle increases in incubation temperatures. This predictable pattern of sex ratio variation creates the potential for sex-specific maternal effects mediated by oestrogens, and furthers our understanding of how moms may influence offspring.

Image caption: Mothers increase yolk oestrogen levels and the production of female offspring across the nesting season .
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The wind, the wind, the heaven-born wind! Forest windthrow effects on soil carbon dynamics

Mathias Mayer, Hans Sandén, Boris Rewald, Douglas L. Godbold, Klaus KatzensteinerImage provided by authors.

Forests are the predominant terrestrial sinks for atmospheric carbon dioxide (CO2). However, forest disturbances, such as insect attacks or windthrows (from storm events) can negatively affect the carbon (C) balance of a forest ecosystem. Climate change is likely to intensify these disturbance regimes in the future. A precise quantification of disturbance effects on the C dynamics of forests is key to lower uncertainties of their C sink capacities.

Soils are the largest C pool in forests and the CO2 efflux from soils represents the largest C flux to the atmosphere. Our understanding of how forest disturbance affects the sources of soil CO2 efflux, namely autotrophic (from roots and associated microorganisms) and heterotrophic soil respiration (from decomposition of dead organic matter), is however poor.

In this study we investigated the impact of forest windthrow on the sources of soil CO2 efflux, underlying biotic and abiotic drivers (i.e. plant community composition, soil organic matter properties and soil temperature and moisture), and consequences for soil organic C stocks in a temperate forest ecosystem in the European Alps.

We found that windthrow had no obvious effect on soil CO2 efflux in the first years after disturbance, because a reduction in autotrophic soil respiration was offset by a ~60% increase in heterotrophic soil respiration. Since all trees were blown over at the research site, an increase in heterotrophic soil respiration was principally related to higher soil temperatures. Autotrophic soil respiration was mainly driven by grasses and herbs rather than young trees in the first six years after disturbance. However, abundant symbiotic soil fungi (ectomycorrhiza) suggests an important indirect tree contribution to autotrophic soil respiration after windthrow. Soil C stocks significantly declined over the post-windthrow period.

Our results show that heterotrophic soil respiration was by far the dominant source of soil CO2 efflux after forest windthrow. Since C losses from heterotrophic soil respiration and soil organic C stocks were of the same order of magnitude, this study demonstrates that a decline in soil C stocks after windthrow was mainly driven by a temperature-related increase in heterotrophic soil respiration and thus decomposition.

Image caption: Image provided by authors.
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Shade tolerance and the functional trait – demography relationship in temperate and boreal forests

Although shade tolerance is a fundamental concept in forest ecology, its definition is complex, and there is still open debate about what confers the ability of species to withstand shade conditions, and how shade tolerance is related to growth and mortality. Here, we hypothesize that shade tolerance can be achieved by alternative combinations of traits depending on the type of tree (deciduous vs. evergreen), and that its relationship with growth and mortality will also vary across these groups. We collected data on 48 tree species (23 evergreen and 25 deciduous species) from 10 sites in temperate or boreal forests across 4 continents. We identified the main traits (leaf characteristics, seed mass, wood density, etc.) that helped predict species growth and mortality, and whether these traits were related to shade tolerance. To test different hypotheses about the relationship between traits, shade tolerance, growth and mortality we used a technique called “structural equation modelling”. This technique allowed us to confirm that the traits involved in shade tolerance are different for evergreen than for deciduous trees, making an interesting contribution to the debate on the nature of shade tolerance. For instance, according to our results shade tolerance may be a good example of convergent evolution, that is, the parallel adaptation of evolutionarily distant species to the same condition (shade) but possibly using different strategies. Moreover, if researchers want to use shade tolerance as a predictor of forest dynamics and species coexistence, they should first be sure about the role it plays in the demography of the species under study.

Image caption: Image provided by authors.
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Honest floral colour change to maintain a long-lasting relationship with pollinators

Takashi T. Makino and Kazuharu Ohashi A bumblebee collecting nectar from an artificial flower. (photo by Takashi T. Makino).

Floral colour change, reported in hundreds of plant species, is a well-known example of ‘honest signalling’ in plant–pollinator interactions. It occurs in fully turgid flowers, and usually correlates with a cessation of reward production (such as nectar) in individual flowers. The question is “Why do these plants honestly tell pollinators which flowers are rewarding?” In previous studies, the trait has been considered a plant strategy that enhances distant pollinator attraction, while minimizing visits to non-reproductive flowers at close range.

Here, we propose an additional benefit of floral colour change, which emerges when we consider the spatial learning ability of pollinators to avoid unprofitable plants. If a plant retains rewardless flowers without colour change, it is difficult for pollinators to visually locate the rewarding flowers. Although the enhanced display initially attracts more pollinators, its low profitability for foraging may discourage them from returning to the plant. This plant-level avoidance resulting from rewardless flowers may be prevented by floral colour change because it helps pollinators to find rewarding flowers. To test this possibility, we observed the behavioural changes of bumblebees foraging in an array of artificial plants.

We found that the retention of rewardless flowers without colour change could initially attract bees by increasing the plant’s display size, but their lack of reward resulted in plant-level avoidance by those bees that used spatial memories when choosing plants. The colour change in rewardless flowers, in contrast, encouraged bees to return by helping them to find rewards on plants. Consequently, honest plants with floral colour change received more visits by bees than those dishonest plants that did not display colour change. Floral colour change thus can prevent plant-level avoidance, and thereby enable plants to maintain a long-lasting relationship with experienced pollinators. For employing learning pollinators such as bumblebees, honesty may be the best policy.

Image caption: A bumblebee collecting nectar from an artificial flower. (photo by Takashi T. Makino).
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The structure of flower-visitor networks in relation to pollination across an agricultural to urban gradient

Panagiotis Theodorou, Karoline Albig, Rita Radzevičiūtė, Josef Settele, Oliver Schweiger, Tomás E. Murray and Robert J. PaxtonImage provided by authors.

Pollination is a major ecosystem service in which insects play an important role for the reproduction of most flowering plants, including crops. Among the major threats to insect pollinators, and consequently pollination services, is land use change. However, few studies have addressed the relative effects of (i) local habitat and (ii) anthropogenic land use on local plant-flower visitor community structure, the architecture of flower-visitor mutualistic networks and potential knock-on effects for the ecosystem service of pollination.

In our study, we performed a landscape-scale experiment using insect pollinator-dependent plant communities as ‘pollinometers’ and empirically examined the relative effects of local and landscape drivers on pollination. Using a statistical technique termed Structural Equation Modelling to analyse our empirical data, we found that plant-flower-visitor communities and their mutualistic networks were largely influenced by local factors. In addition, there were positive and correlated effects on the ecosystem service of pollination of (i) increasing urbanization in the surrounding landscape, (ii) flying insect abundance and (iii) bee richness. Yet, we surprisingly found that mutualistic network metrics were themselves largely independent of pollination service provision.

Our findings show that, in moderately urbanized areas providing rich floral resources, positive effects on both bee richness and plant reproduction can be observed. From a theoretical perspective, it is noteworthy that we did not find a relationship between flower-visitor network metrics and pollination of four experimental plant species, challenging the notion that flower-visitor networks can be used as surrogates for the ecosystem service of pollination. From an applied perspective, and as cities expand worldwide, the strong effects of local habitat on pollinator communities further emphasize the potential for local management as a tool for biodiversity conservation in urbanized areas.

Image caption: Image provided by authors.
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To bask or not to bask? Lizards do not follow current theory

Christine H. Basson, Ofir Levy, Michael J. Angilletta Jr., Susana Clusella¬TrullasBasking lizard. Image provided by authors.

One means by which lizards can maintain favourable body temperatures is by thermoregulating. For example, they can shuttle back and forth between sites with sun and shade. However, depending on the availability and distribution of favourable sites, basking may become a costly activity. Longer distances or more time spent moving and searching for optimal sites should involve higher energetic costs. According to theory, lizards should abandon searching for favourable sites when the costs of doing so surpass the benefits and when this net difference is higher than when lizards passively track their surrounding temperatures. In this study, we compared data from a virtual (computer-simulated) lizard that either used an optimal behaviour by maximizing the net benefit of shuttling between available basking sites or used a passive behaviour. We simulated two environments: a ‘poor’ environment which only had one suitable basking site versus a ‘good’ environment which had multiple basking opportunities shifting throughout the day. We then compared the results of these simulations to the results for real lizards placed in experimental arenas with a single or multiple basking sites in the laboratory. Surprisingly, we found that our real lizards do not follow the predictions of the theoretical model. In both environments, lizards searched for basking sites despite the high costs of doing so in the ‘poor’ environment. We revealed that costs were associated with missed opportunities, such as less time available to explore the arena, rather than costs associated with energy spent moving between basking sites. These results highlight that the prediction of thermoregulatory behaviour, to bask or not to bask, depends on the complexity of the habitat mosaic formed by sun and shade sites in the landscape. Flat arid areas, deserts or dense tropical forests are likely to impose high energetic costs if optimal sites are scarce, while temperate and more variable environments may impose non-energetic costs, such as missed opportunities.

Image caption: Basking lizard. Image provided by authors.
Read the article in full here.

 

Stay cool or warm up? Individual differences in energy-saving have consequences for survival and reproduction

Melanie Dammhahn, Manuelle Landry-Cuerrier, Denis Réale, Dany Garant and Murray M. HumphriesEastern Chipmunk (Tamias striatus).

Energy is in short supply for most animals. Therefore, individuals have to find a balance between investing energy into growth, body maintenance and reproduction. During times of food scarcity and unfavorable temperatures many mammals go “on stand-by” and reduce their energy and water requirements by entering into torpor, a reversible state of reduced body temperature, metabolism and activity. Here, we asked whether individual variation in torpor use has consequences for survival and reproduction. We recorded body temperature of individuals of free-ranging eastern chipmunk (Tamias striatus), a small squirrel species that hoards food in a burrow and hibernates during winter. Using small temperature loggers, placed around the neck of animals, we continuously recorded skin temperature over the whole winter. We found that individuals of the same population differ from each other in how much torpor they use on average over the winter, even though they are exposed to similar environmental conditions. This among-individual variation had consequences for winter survival and reproductive success in the following breeding season. Individuals using less torpor at the beginning of the winter had decreased survival in resource-rich but not in resource-poor years, and higher reproductive success in the subsequent breeding season. Thus, whether it is beneficial for an individual chipmunk to stay cool and save energy, or to warm up and reduce the costs of torpor and prepare for reproduction, depends on local environmental conditions. Since individuals are the target of selection, we think that considering individual variation in eco-physiology can contribute to a more thorough understanding of the evolution of energy-saving strategies in mammals.

Image caption: Eastern Chipmunk (Tamias striatus).
Read the article in full here.

 

Functional traits of marine macrophytes predict primary production

Holger Jänes, Jonne Kotta, Merli Pärnoja, Tasman P. Crowe, Fabio Rindi and Helen Orav-KottaImage provided by authors.

Large seaweeds and higher plants (macrophytes) are commonly found in coastal marine habitats where they photosynthesise i.e. they build up their own organic compounds by using the sun’s energy. Primary production underpins aquatic food webs, plays an important role in the global carbon cycle and connects the life from surface ocean layers with the species at the seabed. However, the rate of primary production can greatly vary between species, communities, ecosystems, seas and oceans, simply because species differ in terms of their functional setup and oceans in their environmental settings. Here we investigated the possibility to link functional traits (i.e. biological characteristics) of macrophytes from the major European seas to primary production and we asked if there were specific functional traits that could be effectively used to predict primary production of macrophyte communities.

We first measured primary production of macrophyte communities and then quantified how large fractions of the total community biomass different traits compose. By linking community production and trait information we found out that primary production mostly depended on the amount of large epilithic seaweeds of marine origin in the community. Interestingly, we also found that several traits were clustered together meaning that the occurrence of one trait increased the likelihood of another. Our findings suggest that functional traits of macrophytes can be effectively used to monitor primary production. Furthermore, taxonomically distinct species might possess similar traits meaning that functional aspects of ecosystems can be analysed without extensive taxonomic knowledge. This could result in simplification of the general procedure of production estimations and establish transparent framework how to link community structure with functioning.

Image caption: Image provided by authors.
Read the article in full here.

 

Are certain types of plumage colours more likely to differ between males and females?

Kaspar Delhey & Anne PetersImage provided by authors.

In many birds males and females show different colours and often males are more colourful than females, a phenomenon called sexual dichromatism. More colourful males are generally favoured by females. But why would females choose males based on their colours? One hypothesis states that females choosing colourful males are selecting mates of higher quality. Consequently, sexual selection should lead to the elaboration of colours that honestly signal quality and these should be more sexually dichromatic.

Certain types of plumage colours, for physiological reasons, may constitute better signals of male quality. Among these are carotenoid-based colours. Carotenoids are yellow to red plant pigments that animals need to ingest in their food and which also play important roles in immune function and health maintenance. These links with food and health, which are particularly strong for red carotenoids, make them good candidates to be sexually selected and dichromatic. Other pigments, such as melanins, are produced within the body and are considered cheaper to produce. Colours can also be produced by the interaction between light and feather microstructure, known as structural colours, which often have blue, violet or ultraviolet hues.

Here we quantify sexual dichromatism for colours produced by different mechanisms (including carotenoids) in a large sample of Australian birds. By measuring plumage colours on museum specimens and using models of bird colour vision we could estimate how different male and female plumage colours look to birds.

In general, sexual dichromatism was highest when males and females had plumage coloured by different mechanisms of colour production (e.g. males by carotenoids and females by melanins). This is not surprising, since colours caused by different mechanisms are usually quite different. We also found that, as predicted, red carotenoid plumage had higher sexual dichromatism and that species with a higher proportion of their plumage coloured with red carotenoids showed higher levels of sexual dichromatism. However, these correlations did not explain a large amount of variation in sexual dichromatism. We conclude that knowing the mechanisms behind the different types of colours has only limited utility in predicting which colours should be sexually selected in birds.

Image caption: Image provided by authors.
Read the article in full here.

 

Plant communication in a widespread goldenrod: keeping herbivores on the move

André Kessler and Kimberly Morrell Photograph provided by authors.

Plants can exchange information with neighbouring plants and a complex network of herbivores, predators and parasitoids. The language that plants use for such information transfer is, to a great extent, chemical - released into the rhizosphere (the soil immediately surrounding the roots) or into the air surrounding the plant. Chemical communication between neighbouring plants through airborne volatile organic compounds (VOCs) has to date been documented in over 35 plant species spanning 16 families; however, the underlying mechanisms through which it shapes plants’ ecological interactions remain less clear. Using a combination of field/laboratory bioassays and airborne volatile and leaf chemical analyses in tall goldenrod (Solidago altissima), we tested the hypothesis that plant-to-plant communication affects the performance, feeding and movement behaviour of herbivores by changing plants’ chemical phenotypes. We found that plant communication accelerates herbivore movement between host plants while simultaneously reducing herbivory. This suggests that plant communication can limit herbivore loads by keeping herbivores on the move between host plants.

We also demonstrate that volatile chemicals emitted from herbivore-attacked plants are sufficient to explain metabolic responses in, and ecological consequences for, the exposed neighbour plant. Thus, volatile organic compounds emitted by stressed plants provide neighbouring plants with specific information about herbivores in the vicinity. The attacking herbivores, in turn, respond similarly to directly damaged plants and plants exposed to VOCs from damaged neighbours, as if they were of equivalently poor quality.

This study suggests that by enlarging the spatial scale at which induced resistance affects the distribution of plant chemical phenotypes in plant populations, VOC-mediated plant communication alters the movement behaviour and performance of herbivores.

Image caption: Photograph provided by authors.
Read the article in full here.

 

Plant genotype identity and intra-specific diversity trump soil nutrient availability to shape old-field structure and function

Lara Souza, Katharine L. Stuble and Aimeé T. ClassenPhoto provided by authors.

Biodiversity, often measured as the number of species in a community, can promote services within ecosystems such as sequestration of carbon from the atmosphere. Biodiversity within a species, or specifically the number of genotypes within a species, may be just as important in promoting ecosystem services, especially when considering a common species. Solidago altissima, also known as tall goldenrod, is a commonly found plant in abandoned agricultural fields ranging from Florida into northern Canada. Tall goldenrod can make up almost half of the total productivity of old fields and is associated with a large number of insects including herbivores, predators and pollinators. To explore the role of biodiversity within tall goldenrod, and how the environment may influence biodiversity effects on ecosystem services, we established a field experiment where Solidago genotypes occurred in monocultures vs. mixtures under ambient vs. added soil nutrients, to mimic the variability of resources found across space and time. Our findings indicate that plant genetic variation, and to some extent plant genotypic diversity, strongly influence carbon sequestration in old fields, and such effects took place regardless of soil nutrient availability.

Image caption: Photo provided by authors.
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Fire ant queen choices are behind fire ant success

Walter Tschinkel and Joshua KingThe experimental plots in the Apalachicola National Forest in Florida. Several tilled plots and shade covers are apparent.

One of the basic questions of ecology is how and why particular sets of species (called communities) live together; to what degree does the physical nature of the habitat limit the species present, and to what degree do species' interactions? Solid answers to such questions cannot be derived from the existing species co-occurrence, but must be derived from experiments.

The fire ant, Solenopsis invicta, is an exotic, invasive ant found primarily in human-disturbed habitats, and is absent from most undisturbed, native habitat such as the coastal plains pine forests of northern Florida. However, fire ants quickly colonize soil and vegetation disturbances in these forests and thrive until these revert in time to a less disturbed condition. We previously showed that soil disturbance reduces the native ant populations. Newly-mated, dispersing fire ant queens locate these disturbances while in flight and settle in them preferentially to try to establish new colonies. The question is, do they know what they are doing? Does settling in such sites improve their chances of success?

We set up experimental plots in a Florida pine forest with all combinations of soil tilling, shading and reduction of the native ant community (using poison baits). We then planted newly-mated fire ant queens, incipient colonies and small colonies in these plots and followed their survival. Survival of newly-mated queens and incipient colonies was extremely low, but those that did survive were exclusively in plots in which native ants had been reduced and/or the soil disturbed. Planted small colonies fared much better: in plots with reduced native ants, 21 of the 108 planted colonies (19%) were still alive 15 months later, while in plots with an intact native ant population, less than 2% of the 108 colonies survived.

By choosing to land in disturbed habitat with its reduced native ant population, newly mated fire ants queens increase their chances of successful colony establishment. This ant community is thus assembled primarily by queen habitat choice and secondarily by competition. Queens do know what they are doing.

Image caption: The experimental plots in the Apalachicola National Forest in Florida. Several tilled plots and shade covers are apparent.
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Tree height, not fruit shape or weight, predicts how far wind dispersed seeds fly

Carol K. Augspurger, Susan E. Franson, and Katherine C. Cushman A representative dispersal unit of each of 12 wind-dispersed study species in Panama.  The results show that tree height and number of dispersal units, and not how fast the dispersal unit falls, explain the pattern of seeds distributed around the parent tree.Image provided by authors.

Seeds that disperse further from their parent tree often have a better chance of survival. Seed dispersal may send a parent’s offspring to areas with more light, and therefore improved growth. Also, offspring may arrive in areas of lower seed density and away from the parent tree where fungi and herbivores are less likely to attack them. However, how a parent controls where its offspring are dispersed is unclear. This study provides insights into factors critical in predicting the pattern of seeds that fall around a parent tree. This pattern is important because dispersal determines how many of a parent’s offspring survive.

Here, we studied wind-dispersal by 12 Panamanian tree species. Our results showed that dispersal units with a higher weight to area ratio fell faster in still air. However, this speed of fall did not predict dispersal distance when many dispersal units were released from a 40 m tower in the forest. Likewise, these traits did not explain how far a seed landed after natural dispersal from the parent tree.

The pattern of seeds around parent trees of the 12 species differed greatly. We found that taller trees had greater average and maximum seed dispersal distances. Trees dispersing a greater number of seeds also had a greater average dispersal distance. In contrast, a seed’s speed of fall in still air, which is related to how long it is exposed to winds, was not important. Generally, the tree variables predicted dispersal distance well, but unaccounted factors about the dispersal unit or the parent tree, or, more likely, variation in wind speeds that seeds experienced after release, were also important.

Therefore, tree traits explained dispersal distances of these wind-dispersed species, particularly over long distances where offspring survival is enhanced. Apparently, a taller tree exposes its seeds to stronger winds, particularly updrafts after they are released, and carries them to farther distances and lower densities, and perhaps to higher light where some offspring may survive. Future studies should focus on wind strengths needed to release the seeds from the tree, as well as wind patterns after release, to improve our understanding of dispersal.

Image caption: A representative dispersal unit of each of 12 wind-dispersed study species in Panama. The results show that tree height and number of dispersal units, and not how fast the dispersal unit falls, explain the pattern of seeds distributed around the parent tree. Image provided by authors.
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Intraspecific trait variation across multiple scales: the leaf economics spectrum in coffee

Adam Martin, Bruno Rapidel, Olivier Roupsard, Karel Van den Meersche, Elias de Melo Virginio Filho, Mirna Barrios and Marney Isaac Photograph provided by authors.

Ecologists are interested in knowing how changes in biodiversity affect ecosystems. Specifically, they are often interested in understanding how biodiversity losses reduce the “services” that ecosystems provide. In agricultural systems for example, we are interested in knowing how reduced diversity affects crop yield, pest outbreaks, or crop responses to climate change. For a long time, ecologists have measured biodiversity simply as the number of species in an ecosystem. But more recently they are interested in “functional diversity”: in other words, the range of leaf, root and stem types that are present in an ecosystem.

Generally, functional diversity is a better predictor of ecosystem services than simply the number of species, so it has become important to know which are the most ecologically important functional traits in plants. Leaf functional traits – notably, photosynthetic rates, the amount of nitrogen in a leaf, and leaf mass per area – get the most attention. One main way ecologists have come to know these traits are ecologically important is by examining how they relate to one another. Looking at the leaves of hundreds of species, they have uncovered general trends in plants globally: as leaf nitrogen goes up, photosynthesis goes up, and leaf mass per area goes down.

While we know this happens across plant species in natural ecosystems (or “wild” plants), we are still unsure i) if these relationships occur when we look across different individuals of the same species, or ii) if these relationships in wild plants also occur in crops, which have been domesticated over many years.

We looked at these questions in coffee, one of the world’s most common (and well-loved) crops. We found that the same leaf traits that are ecologically important in wild plants are also ecologically important in coffee. Specifically, we found that across nearly 400 leaves from 100 coffee plants, as leaf nitrogen goes up, photosynthesis goes up, and leaf mass per area goes down. But in coffee, these relationships are not the same as in wild plants, possibly because coffee has been bred to have a lot of caffeine, much of which may be in leaves.

Image caption: Photograph provided by authors.
Read the article in full here.

 

Climate and tree vigour control the timing of wood formation in deciduous oaks

Gonzalo Pérez-de-Lis, José Miguel Olano, Vicente Rozas, Sergio Rossi, Rosa Ana Vázquez-Ruiz and Ignacio García-GonzálezTransverse section of wood from pedunculate oak (Quercus robur). Dividing cells in the cambial zone (centre) give rise to new phloem (top) and xylem (bottom) tissues.

Trees produce new wood during their whole lifespan. Tissue known as ‘vascular cambium’ generates a new tree ring that is disposed over the existing wood tissues every year. To sustain the machinery of growth, trees need to invest large amounts of carbohydrates produced in the leaves via photosynthesis. Trees adjust how they function in different climates by shifting the timing of growth (i.e. phenology), although this can influence the capability of trees to produce wood. Understanding how phenology affects wood production is of special relevance in the context of climate warming, which is modifying phenological patterns in terrestrial plants.

We monitored wood and leaf formation, and the content of non-structural carbohydrates (NSC), in the stems of two deciduous species, pedunculate oak (Quercus robur) and Pyrenean oak (Quercus pyrenaica), in three sites located along a humidity gradient in northwestern Spain. Although Pyrenean oak is better adapted to drought than pedunculate oak, both species coexist along the transition between the temperate and Mediterranean regions. We also assessed the impact of the number of cambial cells in winter (higher in more vigorous trees) on wood production and phenology during the following growing season.

Pedunculate oak was more productive and had a longer growing season than Pyrenean oak, but both species showed comparable seasonal changes in growth activity and carbon reserves. We show that, under warm and dry conditions, deciduous oaks reduce or even stop growth in summer, but extend the growing season in spring and autumn. Stem NSC dropped in spring simultaneously with the onset of growth, and recovered in summer after the formation of new leaves. Trees with more cambial cells in winter had a longer growing season and produced more wood. This result indicates that tree vigour acts as a predisposing factor for growth, modulating carbon demands throughout the year.

Image caption: Transverse section of wood from pedunculate oak (Quercus robur). Dividing cells in the cambial zone (centre) give rise to new phloem (top) and xylem (bottom) tissues.
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Integrating intraspecific variation in community ecology unifies theories on bodysize shifts along climatic gradients

Alice Classen, Ingolf Steffan-Dewenter, William J. Kindeketa, Marcell K. PetersImage provided by the authors.

Species traits, like the size and shape of organisms, change along broad-scale climatic gradients. Probably the most famous biogeographical pattern in this context is Bergmann’s rule, which says that species tend to get larger in cooler environments. This has been explained by the fact that species with larger body sizes are energetically favoured because they lose less heat, in relative terms, due to a reduced surface-to-volume ratio. An alternative hypothesis is that energy availability effectively limits the maximum size of organisms. Absolute energy requirements of larger organisms are higher than those of smaller organisms, i.e. they need more energy and space to maintain critical population sizes and are predicted to face higher extinction risks in energy-limited environments. Thus, the predictions concerning body size distributions are contradictory.

Tropical mountains provide excellent conditions to study the patterns and drivers of species traits, as here potential drivers like temperature, area and resource availability change rapidly, making ecological studies feasible. In this study we analysed the body size distributions of wild bees on the highest free-standing mountain in the world, Mount Kilimanjaro (Tanzania). As we assumed that different drivers may operate at different levels of biological organization we studied trends in body size at both the community and species level.

We show that Bergmann´s rule and energy-based predictions are both evident in bee communities along the elevational gradient of Mt. Kilimanjaro. While individuals within species became on average larger with increasing elevation, communities in cooler habitats were increasingly dominated by smaller species. Thus, whether evidence for one or the other hypothesis is found depends on the level of biological organization. We conclude that the integration of intraspecific variation into community ecology can unify conflicting theories on body size shifts along temperature gradients.

Image caption: Image provided by the authors.
Read the article in full here.

 

Wood anatomy reflects different ecological strategies in tropical rainforest lifeforms

Deborah M.G. Apgaua, David Y.P. Tng, Lucas A. Cernusak, Alexander W. Cheesman, Rubens M. Santos, Will J. Edwards and Susan G.W. LauranceAnatomy of a rainforest liana Strychnos minor showing large and largely solitary vessels. Image provided by the authors.

Tropical rainforests harbour a large portion of the world’s plant diversity, yet many scientists fear these communities are at risk from increasing drought events. In order to understand how forests with thousands of species will respond to droughts, we explored how plants that live in different parts of the forest differ in form and function.

We studied 90 plant species in a lowland rainforest in northeast Australia that differed in their habitat preferences, ranging from the dark understorey to the tops of trees. These species formed six ecological groups: mature-phase trees, understorey trees, pioneer trees, understorey shrubs, pioneer shrubs and vines. We sampled wood from these species to collect data on anatomical features related to water transport, such as vessel sizes, frequency and distribution. We also collected leaves from each species to quantify leaf intrinsic water use efficiency through carbon isotope ratios, a measure of how much carbon could be taken up by photosynthesis for a given amount of water lost to transpiration.

Across our study species, we found a spectrum of different wood characteristics. Large climbing plants called lianas, for instance, had low wood densities and exhibited large solitary vessels, indicating an ecological strategy that maximizes water transport at the expense of mechanical support. At the other end of the spectrum, understorey shrubs and trees had high wood densities and numerous small vessels, possibly reflecting a higher investment in structural support, and the reduced need for high water transport. Vessel size was also a strong predictor of water use efficiency across our 90 study species, indicating that plants with larger vessels, and thus a higher potential for water transport, are able to fix more carbon per unit of water transpired. We therefore provide a framework for understanding plant performance through wood functional anatomy and a plant functional group approach.

Image caption: Anatomy of a rainforest liana Strychnos minor showing large and largely solitary vessels. Image provided by the authors.
Read the article in full here.

 

Mosses in Californian grasslands in a changing environment

Risto Virtanen, Anu Eskelinen and Susan Harrison A view over the experimental site at McLaughlin Nature Reserve (Inner Coastal Ranges, California) with harsh serpentine (background) and non-serpentine grassland (foreground). The green grassland patches in the middle of harsh serpentine are created by simulated eutrophication and increased rainfall. In these grasslands, typical bryophytes include Didymodon vinealis (left insert) and Fissidens sublimbatus (right insert). Photos by Anu Eskelinen and Risto Virtanen.

Bryophytes (mosses) are small spore-producing plants that occur in most global ecosystems. Even where they are relatively scarce, such as in semiarid grasslands, bryophytes still may play important roles in various processes such as nutrient cycling, surface water dynamics or vascular plant regeneration. Human impacts such as projected climate shifts and nutrient deposition are likely to change both the abundances and the ecological role of bryophytes.

We simulated two environmental changes, increased springtime rainfall and increased nutrient availability, in a semiarid grassland in California. Both of these changes are already known to make grassland plant communities more productive and more strongly dominated by tall vascular plant species such as exotic annual grasses. In turn, this increase in productivity has been shown to suppress the abundance and diversity of smaller vascular plants, many of which are native annual forbs (“wildflowers”). We asked whether bryophytes would show this same competitive suppression of abundance and diversity under enhanced rainfall and nutrients.

As predicted, both bryophytes and small vascular plants declined under our rainfall and nutrient addition treatment as biomass and tall plant dominance increased. In contrast, adding water alone benefited bryophytes but not small vascular plants, while adding nutrients alone benefited small vascular plants but not bryophytes. In general, our results support the idea that environmental changes that enhance grassland productivity and dominance of tall vascular plants are likely to harm grassland diversity, including bryophytes as well as small vascular plants.

Image caption: A view over the experimental site at McLaughlin Nature Reserve (Inner Coastal Ranges, California) with harsh serpentine (background) and non-serpentine grassland (foreground). The green grassland patches in the middle of harsh serpentine are created by simulated eutrophication and increased rainfall. In these grasslands, typical bryophytes include Didymodon vinealis (left insert) and Fissidens sublimbatus (right insert). Photos by Anu Eskelinen and Risto Virtanen.
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How will climate change affect predatory invasive species?

Brian S Cheng, Lisa M Komoroske and Edwin D GrosA predatory Atlantic oyster drill rests upon an Olympia oyster. In many parts of the world, oyster drills have been accidentally introduced and may pose a problem for native oysters. These negative effects may intensify with climate change. Oyster drill egg capsules can also be seen on the right side of the photo. Photo credit: Brian Cheng.

The spread of invasive species has resulted in tremendous economic impacts and losses to biodiversity across the planet. There is concern that climate change may worsen the impacts of invaders, partly because many of these species appear to be more tolerant of changing environmental conditions than their native counterparts. However, most of our knowledge in this area is from alien species that are taxonomically related to or that compete with natives. Invasive predators are among the most disruptive non-native species, yet we know almost nothing of how these animals may respond to climate change. To address this, we examined the physiology of two invasive predators (oyster drills – predatory sea snails) and their native prey (oysters) to understand how these species may respond to warming and extreme flood events. We found that these predators were generally less tolerant of extreme climate change conditions as compared to their prey. However, when animals were exposed to conditions representing near-term warming, predator performance and foraging on prey oysters increased greatly. These observations are supported by previous field measurements that indicate intense predation on oysters at the warmest sites. In addition, both invasive predators exhibited different temperatures of peak performance, suggesting that there is a broad temperature range over which predators will consume prey oysters.

Although extreme events appear to favor prey oysters, near-term warming trends may ultimately reduce their abundance in nature. This is a concern, because wild oysters have experienced declines of up to 88% over the last century due to overfishing and habitat degradation. In response, there are active efforts to conserve and restore oyster populations in many parts of the world. Our work suggests that climate change and the invasion of non-native species may severely hamper the recovery of oysters. Future efforts to assist native oysters should consider attempting to eradicate invasive predators that may benefit from climate change.

Image caption: A predatory Atlantic oyster drill rests upon an Olympia oyster. In many parts of the world, oyster drills have been accidentally introduced and may pose a problem for native oysters. These negative effects may intensify with climate change. Oyster drill egg capsules can also be seen on the right side of the photo. Photo credit: Brian Cheng.
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Does differential processing of coral and algal exudates by reef sponges influence dissolved organic matter cycling via the “sponge loop”?

Laura Rix, Dick van Oevelen, Ulrick Struck, Fuad Al-Horani, Christian Wild and Malik NaumannImage provided by authors.

The efficient recycling of nutrients on coral reefs contributes to the characteristic high productivity of these diverse underwater ecosystems. The main primary producers on coral reefs, corals and algae, release large quantities of their excess products from photosynthesis as energy-rich dissolved organic matter (DOM). This DOM represents the largest source of organic matter produced on coral reefs, but most reef organisms that rely on organic matter as a source of energy cannot directly utilize DOM as a food source. Sponges are not only able to consume DOM, but they also transform and release a fraction of the DOM they assimilate as particulate detritus, which can then be used as a food source by many other reef organisms. This sponge-mediated DOM recycling pathway has been termed the “sponge loop” and plays a key role in transferring the energy and nutrients in DOM to higher trophic levels on coral reefs. Interestingly, the DOM released by corals and algae differs in composition and nutritional quality, but the influence of these different DOM sources on recycling by sponges has not been investigated.

We used incubation experiments to compare the processing of coral- and algal-derived DOM by three coral reef sponge species from the Red Sea: Chondrilla sacciformis, Hemimycale arabica, and Mycale fistulifera. We found that the sponges took up and assimilated both coral- and algal-derived DOM into their tissue biomass, but that uptake rates were significantly higher for algal-derived DOM. A substantial fraction (15–49%) of the coral- and algal-derived DOM assimilated by the sponges was subsequently converted into and released as particulate detritus. However, algal-derived DOM was released as detritus at a higher rate. These findings suggest that sponges process and recycle algal-DOM more rapidly than coral-derived DOM. As coral reefs are increasingly threatened by anthropogenic impacts, many corals reefs are undergoing community shifts from coral to algal dominance. By demonstrating that the DOM produced by algae enhances DOM recycling via the sponge loop, our findings have potential consequences for both nutrient cycling and the transfer of energy through food webs on coral reefs.

Image caption: Image provided by authors.
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Moose in disturbed forests: impacts on plant regeneration, litter decomposition and soil composition

Nichola Ellis and Shawn LerouxImage provided by authors.

Herbivores, such as moose, can play an important role in ecosystems. By selectively feeding on certain plant species, herbivores can reduce the growth of their preferred plants and promote growth in those plant species they avoid. Herbivores usually consume plants that are relatively high in nitrogen and phosphorus and avoid plants that are relatively high in carbon and non-palatable toxins. Most of the plant material not consumed by herbivores dies and becomes litter which then decomposes in the soil. Depending on feeding preferences, herbivores can dramatically change the concentrations of carbon, nitrogen and phosphorus in the soil. This could influence plant growth, and the insects, birds and other animals that depend on plants.

Evidence from studies in boreal forests in North American show that moose, via their feeding activities, can change plant communities, decrease the amount of carbon, nitrogen, and phosphorus in soils and decrease the time it takes for litter to decompose. We tested the influence of moose and abiotic conditions, such as climate, on plant communities and soils in Newfoundland, Canada, a temperate marine island with different climatic and environmental history from that in other studies.

We used 10 large fenced areas to exclude moose and found that after 15-20 years of moose absence, both preferred and non-preferred plants were able to grow taller, and produce more litter compared to areas where moose were feeding. However, concentrations of carbon, nitrogen, and phosphorus in soils and litter decomposition time were not impacted by moose, while soil depth and soil pH were higher and lower respectively. Our results suggest that, in Newfoundland, environmental conditions such as moisture and disturbance history may have a greater impact on soil quality and litter decomposition than moose presence. We show that future studies of herbivore impacts on forests should consider the importance of environmental conditions. In Newfoundland, Parks Canada should continue to monitor moose populations and forests to see if the effect of moose on forest ecosystems changes over time.

Image caption: Image provided by authors.
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The outcome of competition between two parasitoid species is influenced by a facultative symbiont of their aphid host

Ailsa H.C. McLean & H. Charles J. GodfrayAphelinus abdominalis parasitizing Acyrthosiphon pisum. Photo by Jan Hrček.

Many insects have close and ongoing relationships with symbiotic bacteria, which can provide a number of different benefits, including defence against natural enemies. In this study, we asked whether this protection can affect how different natural enemies interact with one another; specifically, can symbiont-mediated protection alter the outcome of competition between natural enemies?

We studied aphids which carry a symbiotic bacterium that can provide protection against parasitoid wasps. The wasps lay their eggs inside aphids, and the developing wasp larva eventually kills the aphid, but not until the very end of its development. The symbiotic bacteria can act to kill the wasp at an early stage, but the symbionts are not equally effective against all wasp species. We used a symbiont strain which is known to provide strong resistance against one species, Aphelinus abdominalis, but much weaker resistance against a second species, Aphidius ervi. We asked how this asymmetric protection affects the outcome of competition between these two different wasp species when they lay eggs in the same aphid. In these interactions, only one wasp can develop successfully.

We allowed a female of first one wasp species, then a female of the other wasp species, to lay one egg each in a single aphid and compared the outcome for aphids with and without the symbiont. We asked which wasp species successfully developed, or did the aphid survive? We found that, in symbiont-free aphids, the first wasp to oviposit gained an advantage. However, A. abdominalis never survived in the presence of the symbiont. This allowed A. ervi, which would normally have been the inferior competitor, to develop successfully in aphids with the symbiont, even when it parasitized the aphid second. Our results show that protective symbionts do not only affect the interaction between the host and a natural enemy, but also the outcome of competition at the next trophic level.

Image caption: Aphelinus abdominalis parasitizing Acyrthosiphon pisum. Photo by Jan Hrček.
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Competition shaping the phytoplankton communities, judged from the functional properties of the species

Riina Klais, Veera Norros, Sirpa Lehtinen, Timo Tamminen and Kalle OlliMorphological diversity of phytoplankton, from single cells to different colonies and chains. Photo credit: Dr. Richard Kirby.

Understanding the rules of species coexistence is central for ecological research. Phytoplankton – free-living phototrophic protists and cyanobacteria (the bluegreens) – are known to be controlled by temperature, salinity, light, and nutrients. Species’ environmental preferences define the biogeography and seasonality of phytoplankton functional groups (the most well known being diatoms, dinoflagellates and blue-greens). This knowledge is already used to inform global plankton models. Much less is known about the role of biotic interactions – especially competition – between phytoplankton species in the assembly of natural communities.

We analysed a large coastal phytoplankton dataset, consisting of nearly 8000 samples, collected from the Baltic Sea over the last 30 years, and covering the seasonal cycle and wide salinity and temperature gradients. We first estimated the preferred habitat of every species. From that information, we constructed the simulated communities – as they should be, if only the environment determines community composition. These simulated communities were then compared against the actually observed communities.

We investigated whether the species in the observed community were functionally more or less similar to each other than the simulation predicted. The similarity was judged from characteristics such as body size, ability to fix atmospheric nitrogen, whether they are both auto- and heterotrophic at the same time, whether they swim around, make colonies or chains to change the body shape and avoid predators, and the composition of accessory pigments that phytoplankton use to harvest all the different wavelengths of light that penetrate the water.

When comparing the simulated and observed communities, we found that one in every four communities was notably shaped by competition, because species in it were either too similar, or too dissimilar to each other for their coexistence to be explained only by the environment.

Image caption: Morphological diversity of phytoplankton, from single cells to different colonies and chains. Photo credit: Dr. Richard Kirby.
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Which are the drivers of animal personality: hormone levels or metabolic rates?

Benedikt Holtmann, Malgorzata Lagisz and Shinichi NakagawaColour-ringed dunnock (Prunella modularis) from the Dunedin Botanic Garden, New Zealand. Photo credit Stefanie Grosser.

Animals of the same population often show individual variation in their behaviours, which are consistent over time (i.e. repeatable). For example, some individuals are consistently more active, more explorative or more aggressive than others. While these repeatable behavioural differences, referred to as animal personality, have been described in various species, we still know very little about their underlying mechanisms and how personality differences are maintained. Recent studies in the field of animal personality have proposed that consistent individual differences in hormone levels and/or metabolic rates may be responsible for mediating consistent behavioural differences. Thus, here we investigate the relationship between behavioural and the two proposed physiological traits by testing the hypothesis that physiological traits (hormones vs. metabolism) that mediate consistent individual differences in behaviour exhibit similar or higher time-consistency (i.e. repeatability) compared to behavioural traits.

We systematically reviewed published (and unpublished) data from bird species on the repeatability of hormone levels, metabolic rates and behavioural traits, combining results from all relevant articles. Our analyses revealed that both metabolic rates and behavioural traits were highly repeatable and that repeatability estimates of both traits were of similar magnitude. Conversely, the repeatability of hormone levels was three times lower, suggesting that individual hormone levels are more variable over time. These results indicate that individual differences in metabolic rates, rather than hormone levels, are likely a key mechanism involved in generating consistent individual differences in behaviour.

Moreover, additional analyses revealed three more notable findings. First, repeatability estimates of hormone levels and behavioural traits decrease with increasing interval time between two consecutive measurements. Second, males and females differ in repeatability for behavioural traits. And third, hormone level measurements, taken within a few minutes after the capture of an individual (baseline levels) show higher variation than hormone levels taken at least 30 minutes after capture (stress-induced levels).

By conducting meta-analyses, we show that metabolic rates are likely one of the mechanisms underlying consistent individual differences in behaviour. Future studies are now needed to investigate the relationship between metabolic rates and personality traits in more detail.

 

Aphid-generated indirect interaction network

Yoshino Ando, Shunsuke Utsumi and Takayuki OhgushiFigure showing how aphid created an interaction network through ant-mediated and plant-mediated indirect effects.

A wide variety of herbivorous insects may share a host plant. Since the strength and direction of an interaction between two species can be indirectly altered by a third species, multiple insect herbivores on plants can interact directly and indirectly with each other.

Herbivory can induce morphological and/or chemical changes in plants, thereby affecting interactions with subsequent insect herbivores, called a plant-mediated indirect effect. Although past studies have focused on interactions between co-occurring species, plant-mediated indirect effects can affect plant-associated arthropod communities by connecting species that are separated in time and space. However, little is known about how and to what extent multiple direct/indirect interactions can create an interaction network through plant-mediated indirect effects.

We focused on the potential role of an aphid in creating an interaction network on tall goldenrods, and used an aphid exclusion experiment to examine how the aphid affects the interaction network through aphid-generated indirect effects and its consequence for plant reproductive success .

The aphid played a critical role as a network creator in determining the interaction network. The aphid indirectly decreased co-occurring insects through their removal by ants (an ant-mediated indirect effect). Also, late in the season when the aphid was no longer present, it still indirectly decreased scale insects but increased grasshoppers through aphid-induced leaf regrowth. As a result, aphid-induced leaf regrowth greatly contributed to an increase in the interaction diversity and complexity by connecting co-occurring and temporally-separated herbivores. Moreover, the aphid-generated interaction network could improve the reproductive success of tall goldenrods by increasing seed production.

Image caption: Figure showing how aphid created an interaction network through ant-mediated and plant-mediated indirect effects.
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Insects adapt in real-time to cold but not hot temperatures

Mads Fristrup Schou, Marie Brandt Mouridsen, Jesper Givskov Sørensen & Volker Loeschcke To measure the cold tolerance of small insects, they are distributed individually to small numbered glass tubes, which are lowered into a fluid with a low freezing point (<10°C). Hereafter, several machines work together to perform a controlled decrease in temperature, while every single fly is monitored through the glass. The temperature at which all movement of a fly stops is noted, and is a measure of the cold tolerance. Photograph credit: Mads F. Schou.

The ability of insects to evolve and adapt to an increased or a decreased temperature is receiving a great deal of attention, as a consequence of current and future climate change. But adaptation through evolutionary change, which typically requires multiple generations, is not the only way organisms can adapt. Organisms have a remarkable ability to adjust important traits during their lifetime, to stay well aligned with the environment at hand. One example among many is the drastic change in fur color of snowshoe hares from brown to white before the arrival of winter. Do insects also have the ability to readily adjust their physiology or morphology? If insects can increase their cold tolerance when winter is coming, and increase their heat tolerance as the temperature increases during summer, this may be a short-cut for dealing with the expected changes in temperature during the next century. In an attempt to answer this question we investigated 13 species of fruit flies, with distributions that are either world-wide or restricted to deserts, the cold northern climate or the tropical climate. Throughout the entire life cycle, the flies were reared at one of several different temperatures spanning their entire tolerable temperature range. We then estimated the ability to adjust their physiology and thereby align their tolerance according to the given temperature. All 13 species had a surprisingly strong ability to readily adjust their cold tolerance as a response to rearing temperature. This ability is without doubt central for their ability to survive in natural habitats. Conversely, all species had very limited ability to increase their heat tolerance when reared in warmer temperatures, and some species even suffered a decrease in heat tolerance, likely because the high temperatures stressed them. In conclusion, heat tolerance is a highly fixed trait which is unlikely to be rapidly adjusted within generations as an adaptive response during a changing climate, at least in comparison to the strong response with respect to cold tolerance.

Image caption: To measure the cold tolerance of small insects, they are distributed individually to small numbered glass tubes, which are lowered into a fluid with a low freezing point (<10°C). Hereafter, several machines work together to perform a controlled decrease in temperature, while every single fly is monitored through the glass. The temperature at which all movement of a fly stops is noted, and is a measure of the cold tolerance. Photograph credit: Mads F. Schou.
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Handbook of protocols for standardized measurement of terrestrial invertebrate functional traits

Marco Moretti, André T.C. Dias, Francesco de Bello, Florian Altermatt, Steven L. Chown, Francisco M. Azcárate, James R. Bell, Bertrand Fournier, Michael Hedde, Joaquín Hortal, Sébastien Ibanez, Erik Öckinger, José Paulo Sousa, Jacintha Ellers and Matty P. BergPhotographs of Isopoda  by Theodoor Heijerman.

Traits are simply species characters that can be measured or observed directly and are commonly a descriptor of a behavioural or morphological adaptation. The first well known observation was made by Charles Darwin who famously described the shape of finch bills and their functional relationship with seed size and form. Beyond shape and form, traits strike at the very heart of how individuals increase their survival and fitness in relation to environmental conditions - Darwin’s theory of natural selection brilliantly illustrated that. Relating traits to functions can ultimately provide a measure of how key ecosystem processes and services, like nutrient cycling and pollination, might be affected if communities were to change. Perhaps not surprisingly, the practical side of trait ecology is little different to how taxonomists collect measurements to describe new species: ecologists collect measurements like body size, life span, eye morphology and these are then mapped using a standardized protocol. Measurements are projected in a ‘trait space’ that displays the range and variability of traits of interest, and in doing so, seemingly unrelated species are linked to identify general principles and emergent ideas. Traits have yet to realize their full potential because the methodology is rarely standardized outside of plant ecology, an issue that we try to resolve in this paper for terrestrial invertebrates. We propose the first handbook of protocols for standardized measurements of 29 terrestrial invertebrate traits known to be sensitive to global stressors and to affect key ecosystem processes and services. As has been the case with plants, standardized functional traits will be used in the future to explain invertebrate community assembly, species diversity patterns, and ecosystem processes and services within and across taxa and trophic levels. Meta-analyses across regions and ecosystems will likely highlight future weaknesses and vulnerabilities in communities, as they have done to some extent with pollination. Importantly, we have left room for new knowledge to be incorporated into the trait protocols, using a standard format within which researchers can further provide methodological input for additional special cases.

Image caption: Photographs of Isopoda by Theodoor Heijerman.
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Special Feature: The Ecology of De-Extinction

Using palaeoecology to determine baseline ecological requirements and interaction networks for de-extinction candidate species

Jamie R. Wood, George L. W. Perry, Janet M. WilmshurstCoprolites, such as this of an extinct New Zealand moa, are a source of detailed information on the habitat and dietary requirements, microbiota and parasite communities of extinct species. Photo by J. R. Wood.

One of the main drivers for research into de-extinction (or reviving extinct species) is the potential for returning lost processes and function to modern-day ecosystems. For example, some extinct animals may have been the sole pollinators or seed dispersers for particular plant species, which have now declined themselves as a result of the extinction. Other extinct animals may have played key roles in nutrient deposition, and their extinction may have had major flow-on effects for nutrient cycles. Restoring such species is seen as likely to have beneficial results for ecosystems.

However, this viewpoint focusses mainly on what de-extinction candidates can do for ecosystems. We must also understand and provide the ecological requirements of candidate species, as this will play a key role in determining the success of a de-extinction. Aspects of these include: (i) habitat requirements; (ii) dietary requirements; (iii) microbiota communities; and (iv) parasite communities. Information on these can be challenging to obtain for extinct species, but here we review how different palaeoecological sample types and analytical techniques can be used to gain insights into such requirements. Although palaeoecological data have an important role in guiding and informing the selection of suitable de-extinction candidates, they can only ever provide an incomplete picture, and therefore must complement, rather than replace, observational or experimental data on the resurrected organisms themselves.

Image caption: Coprolites, such as this of an extinct New Zealand moa, are a source of detailed information on the habitat and dietary requirements, microbiota and parasite communities of extinct species. Photo by J. R. Wood.
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Physiological maturity at a critical life-history transition and flight ability at fledging

Allison Cornell, Kate F. Gibson and Tony D WilliamsA fledgling European starling (Sturnus vuglaris) attempts to take off in flight, photo by A. Cornell.

It’s a dangerous world out there for young birds leaving the nest. When songbirds fledge, they make a permanent transition from the sedentary lifestyle of a nestling to a highly active, free-flying fledgling. Outside the nest they have to look for food, escape from predators, and navigate in their habitat. Reported rates of survival show that nearly half of chicks that make this transition die almost immediately, largely due to predators who mark them as easy prey. It’s no surprise that predators choose to go after these juvenile birds; they’re relatively slow to take off, and have poor flight ability.

We investigated the maturity of fledglings on the day they leave the nest, to measure just how developed these young birds are. Consistent with other studies, we found that the values of somatic traits, such as body size and wing length, were smaller than adults. However, when we measured physiological traits that indicate the body’s ability to transport oxygen, we found more than just low trait values. Our fledglings were highly variable in these traits, indicating that this might be a good way to measure the quality of individuals. When we measured the birds’ flight ability, we found that physiological traits were helpful as predictors of take-off angle and energy produced during flight.

When scientists typically study fledglings, only measurements of body size are taken. Our results show that measuring physiological traits might help us distinguish between low and high quality fledglings, because these traits have high individual variation and help predict flight ability. The physiological traits we measured are relatively easy to obtain, and recording these values could greatly impact the way we understand fledglings. If physiological traits are the mechanism driving fledgling flight ability, then for a juvenile bird, physiological maturity could mean the difference between life and death.

Image caption: A fledgling European starling (Sturnus vuglaris) attempts to take off in flight, photo by A. Cornell.
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Review

Does biomass-growth increase in the largest trees? Flaws, fallacies and alternative analyses.

Douglas Sheil, Chris Eastaugh, Mart Vlam, Pieter Zuidema, Peter Groenendijk, Peter van der Sleen, Alex Jay and Jerome VanclayImage provided by authors.

Trees play a major role in the global carbon cycle and our understanding of tree growth informs forest science and management. Yet the characteristic growth pattern of most tree species remains unknown. Until recently most researchers thought that biomass-growth declined at large stem sizes. But recent studies claim to show that biomass-growth increases throughout a tree’s life with no ultimate decline both in forests and in open-grown competition-free environments. Such contrasting views merit careful assessment. Here we examine how methodological issues can influence the detection and interpretation of biomass-growth trends.

Growth studies of large trees pose various challenges. These challenges range from finding enough of such trees (they typically occur at low densities) to measuring them in an accurate and consistent manner (see figure). Correcting stem measurement errors can itself cause biases that increase perceived biomass-growth with tree size. To estimate biomass change from tree measurements requires the size-biomass relationship to be well characterised (calibrated) but for most species and for large stems in general, these relationships remain unknown. Using general species-averaged size-biomass relationships leads to large uncertainties regarding biomass and biomass-growth at large sizes in each species. A problem arises when growth patterns within and among stems are confused (these patterns can be distinct as they reflect distinct ecological processes).

To explore and illustrate some of our concerns we use growth-rings to examine the lifetime growth of 14 tropical tree species. Our examination of estimated biomass-growth in 706 stems indicates similar numbers of positive and negative trends with most trees having relatively flat growth (i.e., without marked trends) over extended periods. Nonetheless, when we compare stems all but one of our 14 species indicate higher biomass-growth in the larger stems. Individual stems and patterns across stems thus lead to contrasting conclusions: any confusion of these would constitute a so called “Ecological Fallacy”.

We note that recent studies concluding that biomass-growth increases as stems grow larger do not in fact examine patterns in individual stems but compare variation in growth among stems. Patterns among stems themselves remain uncertain too, due to errors and possible artefacts. We describe how these problems can be avoided or reduced so as to provide reliable results and conclusions.

Image caption: Image provided by authors.
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Movement ability of an invasive beetle is related to leg length but not body size nor metabolic rate

Pieter A. Arnold, Phillip Cassey, Craig R. White Red flour beetle moving through wheat flour. Schematic of the maze used to assess movement is inset in the top left. Photo: Pieter Arnold.

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Individuals within a species can vary greatly in their ability to move around and disperse within their environment. This variation in movement ability can often be described by physiological, morphological and behavioural traits that are related to dispersal, but the associations among such traits are not always clear-cut or predictable. Previous studies, including work on the invasive cane toad in Australia, have identified that individuals that are larger and have longer legs relative to their body size are able to move farther and faster than smaller or proportionate individuals. In our study, we used an invasive insect species, the red flour beetle, as a model to investigate how movement characteristics related to morphological and physiological traits. Individual beetles were run through a maze that simulated a complex environment, to assess their movement. We identified that movement ability could be described along an axis; individuals that scored positively on this axis moved at higher speed, travelled longer distances, moved continuously, and reached the edge of the maze quicker. Leg length relative to body size was strongly related to movement ability. That is, beetles with relatively long legs had positive movement ability scores, which we hypothesised was because longer legs allow for longer stride length and therefore a greater movement ability. Surprisingly, body size and metabolic rate (energy expenditure) were unrelated to movement ability. This result suggests that dispersal may be more strongly related to the muscles and structures that directly affect locomotion, rather than body size overall or energy-related traits. It will be important for future studies to consider locomotor morphology as a foundation for studying variation in movement and dispersal, especially when investigating the ecology and evolution of traits in invasive or pest species.

Image caption: Red flour beetle moving through wheat flour. Schematic of the maze used to assess movement is inset in the top left. Photo: Pieter Arnold.
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The price of looking sexy: visual ecology of a three level predator-prey system

David Outomuro, Linus Söderquist, Frank Johansson, Anders Ödeen, and Karin NordströmPhoto provided by authors..

Many animals, such as parrots, tropical fish or butterflies, are very colourful. Such colourful displays are favoured in sexual selection as they make the animal stand out, and colour may therefore enhance mating success. However, colour can also be costly, as it makes the animal more conspicuous to both predators and prey. Colourful traits are therefore subject to opposing selection pressures: positive sexual selection by conspecifics (increased mating success) and negative natural selection by predators (higher predation risk) and prey (lowered hunting success). In this paper we studied the conspicuous wing coloration of two species of damselflies, which are predated by birds and prey on small flies. The conspicuous wing coloration is used in colour communication between the sexes and between different species of damselflies. Using electrophysiology, we first determined the colour vision of the damselflies and found that they see well in UV as well as in the human visible range. Second, we measured the wing coloration using spectrophotometry and confirmed that males are more colourful than females. Third, we estimated the predation risk in natural populations by quantifying the predated wings from bird feeding stations, and found that more males than females were consumed. We finally used our data together with previously known colour vision of the bird predator, and the fruit fly prey, to model how visible the wing coloration is in natural environments. We found that males are very conspicuous to bird predators, to other damselflies, and to prey, while females remain predominantly cryptic (i.e. hard to see against the background). This implies that males, but not females, pay a high cost when they use colour to communicate with other damselflies, both in terms of predation risk and visibility to prey. One of our most surprising findings was that male damselflies are unable to discriminate the wing coloration of perching females! We hypothesize that females use this to reduce male harassment, which is very intense in damselflies. Our study demonstrates that by including several levels of interactions in predator-prey systems, we get a more complete understanding of the costs and benefits of being colourful.

Image caption: Photo provided by authors..
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Competing for seed dispersal: evidence for the role of avian seed hoarders in mediating apparent predation among oaks

Mario Pesendorfer and Walter KoenigA western scrub-jay (Aphelocoma californica) searches the branches of a valley oak (Quercus lobata) for acorns at the Hastings Natural History Reservation in Carmel Valley, California. Photo credit: Jenna Kohles.

Species interactions come in many shapes and forms, from predation to mutualisms. Indirect interactions, mediated by a third party, often occur when two or more species share the same generalist predator. When the predators are also seed dispersers, as is the case for many large-seeded trees whose seeds are harvested by seed-hoarding animals, such indirect interactions can shift from seed dispersal mutualism to predation, depending on the relative seed production of the trees that co-occur in a community. Because the shift of mutualistic interactions from one tree species to another results in increased relative predation of the less-dispersed species’ seeds, this indirect effect is termed “apparent predation” – one tree species indirectly preys on the seeds of another.

To investigate the mechanisms underlying apparent predation, we studied the seed predation and dispersal dynamics of valley oaks (Quercus lobata) at Hastings Natural History Reservation in central coastal California, where they mainly co-occur with two other oak species, California blue oak (Q. douglasii) and coast live oak (Q. agrifolia). In the first year of the study, western scrub-jays (Aphelocoma californica), high-quality seed dispersers that scatter seeds across the landscape by hiding them in the ground, attended Q. lobata trees in large numbers to hoard acorns. However, when attending the trees, the jays encountered lots of aggression from another bird species, acorn woodpeckers (Melanerpes formicivorus) that mainly hoard acorns by storing them in so-called granary trees. These low-quality dispersers only help the oaks when they accidentally drop an acorn during transport and thus mainly function as seed predators.

In the second year of the study, Q. lobata and Q. agrifolia acorn crops were similar to the first year, but Q. douglasii crops increased tenfold. With acorns more widely available across the landscape, western scrub-jays only attended Q. lobata trees sparsely, likely to reduce the risk of injury during encounters with the woodpeckers which vigorously defend their preferred valley oaks in year-round territories. The jays have much larger home ranges in the fall and were able to optimise their foraging behaviour by shifting to less-preferred Q. douglasii acorns. As a result, Q. lobata trees experienced a proportional increase in seed predation and almost no seed dispersal from jays. Q. douglasii thus exerted apparent predation on Q. lobata acorns.

Indirect effects mediated by shared seed predators and dispersers may be one of the mechanisms that allows for the co-existence of multiple oak species in forest communities. The variable seed production of each tree species appears to drive seed predation and dispersal dynamics in ways previously not explored. Follow-up studies are necessary to investigate the details of the spatial and temporal variation of such species interactions in order to tease apart the fitness consequences for all the members of the community.

Image caption: A western scrub-jay (Aphelocoma californica) searches the branches of a valley oak (Quercus lobata) for acorns at the Hastings Natural History Reservation in Carmel Valley, California. Photo credit: Jenna Kohles.
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Sexual selection in hybridizing lizards

Hannah E A MacGregor, Geoffrey M While, Jade Barrett, Guillem Pérez i de Lanuza, Pau Carazo, Sozos Michaelides & Tobias Uller A typical Italian male from north-central Italy. Photo by Ben Halliwell.

Populations frequently undergo periods of relative isolation and differentiation that are followed by contact and hybridization (interbreeding). What makes hybridization so striking is the many different ways in which it can act as a catalyst for evolution, such as by accelerating the course of speciation or facilitating adaptation through the exchange of genes. But if members of each population look and behave differently then why does hybridization occur at all? Are some individuals more likely to hybridize than others?

Sexual selection has a reputation for preventing hybridization because females commonly prefer to mate with males of similar genes or traits. But in many animals, including many species of lizard, sexual selection via competition among males is the most important cause of mating patterns within populations. Intuitively, in these species male competition should also influence patterns of hybridization when populations come into contact.

Common wall lizards from north-central Italy have highly exaggerated male sexual traits compared to individuals from Western Europe, having diverged in isolation from one another during the last ice-age. Genetic data from a natural contact zone in northern Italy suggests that hybridization may occur asymmetrically, between Italian males and Western European females. In this study, we used experimental contact zones in outdoor enclosures to investigate the consequences of divergence in male sexual traits (such as body size, testes mass, and colour signals) for male-male competition and patterns of hybridization between Italian and Western European lizards.

During our experiment the Italian males completely dominated the Western European males in aggressive encounters, monopolised high quality territory and the courtship of females, and achieved greater reproductive success. Despite our data suggesting a competitive and reproductive advantage of the Italian males with the most exaggerated traits, these superior Italians were not more likely to hybridize. Instead, hybridization between Italian males and Western European females seems to arise because the Italian males with less exaggerated sexual traits are outcompeted for Italian females but remain competitive relative to the Western European males.

Image caption: A typical Italian male from north-central Italy. Photo by Ben Halliwell.
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The economics of sexual signalling

Thomas M. Houslay, Kirsty F. Houslay, James Rapkin, John Hunt and Luc F. BussièreCrickets.

Sexual selection theory explains the evolution of exaggerated and flamboyant ornaments, displays and mating behaviours in terms of male competition or mating preferences. Such characters are typically costly to produce, but can bring benefits to their bearers: greater mating success for those individuals with the biggest or brightest signals. If an individual produces such signals repeatedly over the course of their adult lifetime, they face ‘trade-offs’ between current and future investment. These trade-offs can create variation in the intensity of signalling at different ages, often interpreted as alternative strategies: ‘live fast, die young’ vs. ‘slow and steady’.

Another possible explanation for this age-related variation is that it is caused by differences in the ability to acquire resources that can be invested in signalling (meaning, for example, that ‘late bloomers’ do not have early investment options). Testing this hypothesis is challenging, not least because measuring both the acquisition and allocation of resources is a difficult task. As an additional complication, an individual’s energetic reserves both affect and are affected by their signalling investment.

Male crickets signal to females using an energetically expensive call, produced by rubbing together their hardened forewings: the more time a male spends calling, the higher his mating success. In this study, we simultaneously manipulated resource acquisition (through diet treatments) and access to females (as a proxy for manipulating sexual signalling) in male decorated crickets (Gryllodes sigillatus). We measured how much time they spent signalling, and how their energy budgets were affected.

Increased diet quality caused increased signalling effort and energy storage, while access to females increased both the likelihood of and time spent signalling. Males with lower resource budgets signalled less, but still suffered energetic losses and reduced lifespan. Our results suggest that energetic constraints, rather than strategic budgeting of resources, led to reduced signalling levels in males with lower acquisition ability. Our findings therefore imply that age-dependent variation in sexual signalling may not represent alternative adaptive strategies. In addition, energetic constraints can help maintain ‘honesty’ in sexual signalling, at least on average: after all, anything spent today cannot be spent tomorrow.

Image caption: Crickets.
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A fundamental problem in finding biomarkers confirmed using feather fault bars in nestling birds

Jelle J. Boonekamp, Rutger Dijkstra, Cor Dijkstra, and Simon VerhulstA female jackdaw (Coloeus monedula) approaching her nest box. Photo by Jelle Boonekamp.

Measuring fitness – essentially the product of survival and reproduction - is central to studies in evolutionary ecology that are aimed at gaining an understanding of natural and sexual selection. But measuring real fitness can be difficult and time-consuming, so fitness biomarkers – traits that predict survival and reproduction – are potentially powerful tools in evolutionary ecology when they can be used as surrogate study end points. For example, most vertebrate species have long reproductive lifespans and therefore valuable time and other resources could be saved by using fitness biomarkers.

Useful fitness biomarkers need to fulfil 2 criteria: (i) they need to be accurate predictors of fitness, and (ii) they need to be sensitive to environmental variation (or experimental manipulation), such that the biomarker successfully links environmental conditions to fitness. However, evolutionary theory predicts that traits that are important for fitness should be well protected (canalized) against the influences of environmental fluctuations, and hence biomarkers that are both accurate fitness predictors and sensitive to environmental conditions may be rare.

Here we tested for this canalization principle using free-living jackdaws. We manipulated the number of siblings in the developmental period to test how strongly developmental conditions affected the number of feather fault bars in tail and wing feathers. Fault bars are deformities on bird feathers associated with developmental stress and can cause feather breakage, thereby impairing flight and insulation. We show fault bars in the tail increased when there were more siblings in the nest, while the number of fault bars in wing feathers was not affected, suggesting tail but not wing fault bar number is sensitive to developmental conditions. In line with evolutionary theory, we found that fault bar number on wings, but not tails, predicted fitness prospects. These results confirm the theory that the development of traits that are important for fitness is strongly canalized.

The canalization phenomenon has implications for the utility of traits as fitness biomarkers, because when traits are good fitness proxies, they are also more likely to be strongly canalised, reducing sensitivity to environmental variation. Intriguingly, there are nevertheless traits that are both sensitive to environmental conditions and predict fitness prospects, and we discuss hypotheses that may explain this paradox.

Image caption: A female jackdaw (Coloeus monedula) approaching her nest box. Photo by Jelle Boonekamp.
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Telomere length and telomerase dynamics in frillneck lizard

Beata Ujvari, Peter A. Biro, Jordan E. Charters, Gregory Brown, Kim Heasman, Christa Beckmann and Thomas MadsenAdult frillneck lizard behind tree.

Much like the plastic tip of shoelaces, telomeres prevent the ends of DNA from fraying during cell divisions. Studies of human cells in culture have shown that telomeres become shorter at every cell division, and when telomeres reach a critically short length (after 50-70 divisions) the cells stop dividing and die. However, many vertebrates produce an enzyme, called telomerase, which replenishes the missing telomere copies. Telomerase not only prevents telomere shortening but is also able to increase the length of critically short telomeres.

In numerous vertebrates, including humans, telomere length (TL) has been shown to decrease with increasing age. Moreover, during recent decades numerous studies have observed an association between TL and organismal survival and/or fitness.

In the present study we therefore investigated how age affected TL and telomerase expression (TE) dynamics in frillneck lizards. We also examined whether TL and TE had any effects on lizard survival. We found that young lizards had short TL, and that TL increased in medium aged lizards but decreased in older cohorts, revealing a curvilinear relationship between TL and lizard age. Higher TE resulted in longer telomeres but in spite of this we did not observe any association between TL dynamics and lizard survival. Instead our results suggest that TL and TE dynamics in frillneck lizards reflect an adaptation to maintain TL above a critical minimum length in order to sustain cellular stability.

Our study has major implications for the role of telomeres in ageing by questioning the significance of TL dynamics as a significant underlying factor in vertebrate survival.

Image caption: Adult frillneck lizard behind tree.
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Cannibalism or burial: undertaking behaviour depends on the change of death cues in termites

Qian Sun, Kenneth F. Haynes, Xuguo ZhouA termite worker consuming a dead worker. Taken by Hu Li.

The ability to detect environmental cues is important for animals to exploit resources and defend themselves against predators and disease. Social insects frequently encounter the dead bodies of their nestmates, which may carry pathogens and could cause an outbreak in the colony. Many social insects dispose of the corpses with a stereotypic behaviour named undertaking behaviour. Ants and honeybees remove the corpses from the nest, but termites that feed on a nutritionally imbalanced woody diet could benefit from recycling rather than discarding nutrients from dead nestmates. Therefore, corpses represent both a food resource and a pathogen risk for termites. As corpses decay with time, the reward from feeding declines and the risk of disease increases. The central goal of our study is to determine how termites regulate this trade-off by detecting chemical cues from corpses. We combined behavioural and chemical analyses to address this question using the eastern subterranean termite, Reticulitermes flavipes.

We found that termites cannibalize the corpses if they are freshly killed, but resort to burying them when the corpses are highly decayed. Such a behavioural switch is mediated by the changes of death cues released by the corpses. Immediately after death, corpses release 3-octanol and 3-octanone. The early death volatile cue, consisting of this alcohol possibly in combination with the ketone, attracts workers to quickly retrieve and consume the bodies, but the two compounds decrease rapidly with time. Correspondingly, there was an accumulation of late death cues, including a blend of phenol and indole, which enable termites to locate the corpses, and a blend of six fatty acids that trigger burial behaviour. Cannibalism is more efficient than burial behaviour, because it requires fewer workers, and also allows termites to recycle nutrients. However, if corpses are not found within the recyclable time frame, burial behaviour could effectively prevent pathogenic propagation.

Our study indicates that the dynamic changes in death cues balance nutritional rewards and infection risks. This post-mortem communication highlights unique adaptations in termites to their feeding habit and social living.

Image caption: A termite worker consuming a dead worker. Taken by Hu Li.
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Bad boys bite, good girls eat their dinner

Alexis Y. Dollion, G. John Measey, Raphaël Cornette, Liza Carne, Krystal A. Tolley, Jessica M. da Silva, Renaud Boistel, Anne-Claire Fabre and Anthony Herrel Image provided by authors.

Cranial morphology is complex and how it evolves remains relatively poorly understood. One of the complicating issues is that the head serves many functions ranging from the protection of the brain and major sensory organs to the control of feeding and drinking, and display and communication. These different functions often impose different and conflicting pressures on the size and shape of the cranium in vertebrates. An additional complicating factor is that the selective factors driving the evolution of cranial shape may differ in males and females. Indeed, whereas in males of many vertebrates, and especially lizards, the head is used in territory defense and male-male combat, this is typically not the case in females. Here we explore these issues in a group of dwarf chameleons from South Africa. We quantify skull, mandible and quadrate shape in 3D using a cross-sectional imaging technique (computed tomography, or CT imaging) and test whether skull shape is related to diet as determined by stomach flushing and maximal bite force capacity. Our results do indeed show strong correlations both between shape and bite force, and between shape and diet. Bite force is also related to diet. However, the observed patterns differ between males and females and suggest that the role of the cranium is not identical in both sexes. Our results shed light on the relevance of sex when relating a lizard’s morphological adaptations to its ecological role, and show the importance of collecting comprehensive data on shape, bite force and diet to unravel the selective pressures that govern the evolution of complex integrated structures such as the skull.

Image caption: Image provided by authors.
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Organic macromolecules and ultraviolet radiation combine in freshwater ecosystems to damage water flea DNA

Raoul Wolf, Tom Anderson, Dag Olav Hessen and Ketil HyllandImage provided by authors.

As a result of reduced acid rain, climate change, and increased vegetation cover, many lakes and rivers in boreal regions currently experience a phenomenon called “browning”. It describes an increasing transport of plant-derived material from terrestrial plants and soil into freshwater, which causes a distinct brown color. The substances responsible for this browning are usually organic macromolecules or humic substances, commonly referred to as dissolved organic carbon, or simply DOC.

Plants and animals living in lakes and rivers can benefit from increased browning, as it protects them from harmful ultraviolet radiation (abbreviated UVR). However, UVR photons can also react with these DOC substances and produce so-called reactive oxygen species (ROS). These are harmful for all organisms, as they can damage cell membranes, proteins and DNA.

The aim of our study was to find out if the interaction of DOC and UVR in freshwater could produce ROS, and if these harmful substances could then cause DNA damage in an aquatic animal. The animals of choice in our experiments were freshwater water fleas of the species Daphnia magna. Despite their name, water fleas are crustaceans and important members of freshwater food webs, and commonly used model organisms. In our experiments, the water fleas were put in artificially browned waters and put under artificial UVR sunlamps.

We found that by themselves, either DOC or UVR produced only modest amounts of harmful ROS, which caused only minor DNA damage in the animals. However, the combination of DOC and UVR resulted in substantial production of ROS, which caused high levels of DNA damage in Daphnia. This points out the importance of indirect and unsuspected effects, by which climate change may affect aquatic organisms.

Image caption: Image provided by authors.
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The Ecology of De-Extinction

De-extinction and evolution

Alexandre Robert, Charles Thévenin, Karine Princé, François Sarrazin and Joanne ClavelPhoto credit: Alexandre Robert.

Some biologists suggest that they can recreate long lost creatures and bring revived lineages back into suitable habitats. However, the potential for this de-extinction process to contribute effectively to the conservation of biodiversity remains unexplored, especially from the perspective of evolution. We discuss the application of the existing evolutionary conservation framework to potential de-extinction projects. We aim to understand how evolutionary processes can influence the dynamics of resurrected populations, and what the potential evolutionary benefits of de-extinction are. In programs aiming to revive long-extinct species, the most important constraints to the short-term dynamics of any resurrected population are their intrinsically low potential to grow and persist, and their poor adaptation to biotic and abiotic changes in the recipient environment. Assuming that some populations of resurrected species can persist locally, they have the potential to bring substantial benefits to biodiversity if the time since initial extinction is short relative to the time scale of evolution. The restoration of lost genetic information could lead, along with the re-instatement of lost ecological functions, to the restoration of some evolutionary patrimony and processes, such as adaptation. However, substantial costs might occur, including unintended ecological and evolutionary changes in the local system, and unintended spread of the species. Further, evolutionary benefits are limited because extinct species that are original from an evolutionary point of view might be those for which de-extinction is the most difficult to achieve practically. Further, the resurrection of a few extinct species does not have the potential to conserve as much evolutionary history as traditional conservation strategies, such as the reduction of ongoing species declines. De-extinction is a stimulating idea, which is not intrinsically antagonistic to the conservation of evolutionary processes. However, poor choice of candidate species, and most importantly, lengthy time scales between a species’ extinction and its resurrection are associated with low expected evolutionary benefits and likely unacceptable ecological and evolutionary risks.

Photo credit: Alexandre Robert.
Read the article in full here.

The Ecology of De-Extinction

A mammoth undertaking: harnessing insight from functional ecology to shape de-extinction priority setting

Molly Hardesty-Moore, Douglas McCauley, Benjamin Halpern and Hillary YoungImage provided by authors.

De-extinction, or the process of resurrecting extinct species, is an idea that once only seemed possible in science fiction films. Rapidly advancing technologies, however, are bringing de-extinction within reach. Most of the scientific discussion of de-extinction has been focused on the methods that could be used to make it operable and the ethics surrounding whether it is right or wrong to bring back once-extinct species. If made successful, de-extinction could prove an interesting new tool for ecologists and conservation biologists. From an ecologist’s vantage point, the great risk in de-extinction is that it becomes overly focused on the fabrication of species that look like once-extinct species – but do not act like them. In this paper we critically evaluate how de-extinction as a science would have to evolve in order to become a tool of strategic value to ecological communities and ecosystems.

We suggest three ways that de-extinction can produce species that resurrect the ecological jobs of extinct species with high fidelity. First, select candidate species that played a unique role in ecosystems and their loss is more likely to have left gaps in the operation of living systems that have not yet been filled. Second, concentrate on species that went extinct recently, rather than older extinctions. Ecosystems change, and the more time that passes the harder it will be for once extinct species to step back into ecosystems and assume their former roles. Lastly, work only with species that de-extinction can bring back to historic abundance levels, because abundance and ecological performance are often tied together. Following this playbook can help ensure that de-extinction does more than produce ecological zombies.

Image caption: Image provided by authors.
Read the article in full here.

 

Conserving rare species when de-extinction is an option

Gwenllian Iacona, Richard F. Maloney, Iadine Chadès, Joseph R. Bennett, Philip J. Seddon, Hugh P. PossinghamThe Huia (Heteralocha acutirostris), is an extinct New Zealand bird species with an interesting dimorphism such that the female has a dramatically longer bill than the male. The last individuals may have survived until as recently as the 1960s. Species such as this are often suggested as candidates for de-extinction: they are recently lost species of significant conservation interest, and the threats that caused their extinction are known. This paper discusses how using a decision theory approach to conservation prioritization can help managers decide if de-extinction of such species is a good idea.   – photographer J.L . Kendrick. Photo courtesy of the New Zealand Department of Conservation.

The technology to revive extinct species (de-extinction) may soon no longer be simply in the realm of science fiction. In the exciting rush to bring back populations of wild mammoths, or moa, or passenger pigeons, we need to take a step back and make sure that the conservation benefits of such an action outweighs any potential perverse negative impacts. We suggest that the decision tools used in modern conservation prioritization approaches can quantitatively and transparently weigh the pros and cons of de-extinction. This is especially relevant to managing a de-extinct species in the wild in systems where there are extant species of conservation concern. While outlining the steps to the process, we discuss the new considerations that would be important if de-extinction was a possible conservation action. One particularly interesting implication of de-extinction would be its capacity to change the biodiversity conservation problem from the current one that is similar to managing non-renewable natural resources, to a version where the management is of a potentially renewable natural resource. This switch opens up a new suite of time preference and risk aspects to rare species management which could change the strategies employed by managers and the possible conservation outcomes. We are not arguing for or against de-extinction. Instead, we are proposing that the technological advances need to be considered within the context of the existing conservation landscape, and that such considerations may include unprecedented modifications to the current species prioritization problem.

Image caption: The Huia (Heteralocha acutirostris), is an extinct New Zealand bird species with an interesting dimorphism such that the female has a dramatically longer bill than the male. The last individuals may have survived until as recently as the 1960s. Species such as this are often suggested as candidates for de-extinction: they are recently lost species of significant conservation interest, and the threats that caused their extinction are known. This paper discusses how using a decision theory approach to conservation prioritization can help managers decide if de-extinction of such species is a good idea. – photographer J.L . Kendrick. Photo courtesy of the New Zealand Department of Conservation.
Read the article in full here.

The Ecology of De-Extinction

How close can we get to bringing an extinct species back to life?

Beth Shapiro A researcher prepares a fragment of mammoth bone for DNA extraction in the Paleogenomics Lab at UC Santa Cruz. Credit: Beth Shapiro.

Over the last five years, de-extinction, which is the term used to describe the idea that extinct species may soon be brought back to life, has received increasing attention in both scientific and public arenas. Discussions about de-extinction tend to concentrate on the ethical and political implications of resurrecting extinct species and, increasingly, to focus on the ecological consequences of releasing resurrected species into the wild. Relatively less attention has been paid, however, to the process of de-extinction itself, specifically whether the technology is sufficiently advanced to bring an extinct animal species back to life.

I review the three main technologies that are being considered at present for de-extinction: back-breeding, cloning via somatic cell nuclear transfer, and genetic engineering. Back-breeding aims to concentrate ancestral traits that persist within a population into a single individual using selective breeding. Cloning aims to create genetically identical copies of an extinct species from preserved cells, which means that this approach may not be feasible for long-dead organisms whose cells, and the genetic material within them, have decayed. Genetic engineering draws on recent advances in both ancient DNA and genome editing technologies, and aims to edit the genome sequence within a living cell so that the sequence more closely resembles that of a closely related extinct species. This edited cell would then be cloned, creating a genetic hybrid between the living and extinct species.

Because the phenotype of an organism is the consequence of the interaction between its genotype and the environment in which it develops and lives, none of these processes will create exact copies of the extinct species that they are attempting to resurrect. Precise replication, however, is not necessary to achieve the conservation-oriented goals of de-extinction. In the majority of ongoing de-extinction projects, the goal is to create functional equivalents of species that once existed: ecological proxies that are capable of filling the extinct species’ ecological niches. It is this application of de-extinction technologies that is likely to have the most positive impact on conservation.

Image caption: A researcher prepares a fragment of mammoth bone for DNA extraction in the Paleogenomics Lab at UC Santa Cruz. Credit: Beth Shapiro.
Read the article in full here.

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