Maternal investment and early thermal conditions affect performance and antipredator responses.

Exposure to increased temperatures during early development can lead to phenotypic plasticity in morphology, physiology, and behavior across a range of ectothermic animals. In addition, maternal effects are known to be important contributors to phenotypic variation in offspring. Whether the 2 factors interact to shape offspring morphology and behavior is rarely explored. This is critical because climate change is expected to impact both incubation temperature and maternal stress and resource allocation. Using a fully factorial design, and Bayesian multivariate mixed models, we explored how the manipulation of early thermal environment and yolk-quantity in eggs affected the morphology, performance, and antipredator behavior of 2 sympatric Australian skink species (Lampropholis delicata and L. guichenoti). We found that juveniles from the hot treatment were larger than those on the cold treatment in L. guichenoti but not L. delicata. Using repeated behavioral measures for individual lizards, we found an interaction between incubation temperature and maternal investment in performance, with running speed being affected in a species-specific way by the treatment. We predicted that changes in performance should influence antipredator responses. In support of this prediction, we found that maternal investment impacted antipredator behavior, with animals from the yolk-reduced and cold treatment resuming activity faster after a simulated predatory attack in L. delicata. However, the prediction was not supported in L. guichenoti. Our results highlight the importance of exploring the multifaceted role that environments play across generations to understand how different anthropogenic factors will impact wildlife in the future.

Sexual selection buffers the negative consequences of population fragmentation on adaptive plastic responses to increasing temperatures.

Whether sexual selection facilitates or hampers the ability to plastically respond to novel environments might depend on population structure, via its effects on sexual interactions and associated fitness payoffs. Using experimentally evolved lines of the seed beetle Callosobruchus maculatus, we tested whether individuals evolving under different sexual selection (monogamy vs. polygamy) and population spatial structure (metapopulation vs. undivided populations) treatments differed in their response across developmental thermal conditions (control, hot, or stressful) in a range of fitness and fitness-associated traits. We found that individuals from subdivided populations had lower lifetime reproductive success at hot temperatures, but only in lines evolving under relaxed sexual selection, revealing a complex interaction between sexual selection, population structure, and thermal environmental stress on fitness. We also found an effect of population structure on several traits, including fertility and adult emergence success, under exposure to high thermal conditions. Finally, we found a strong negative effect of hot and stressful temperatures on fitness and associated traits. Our results show that population structure can exacerbate the impact of a warming climate, potentially leading to declines in population viability, but that sexual selection can buffer the negative influence of population subdivision on adaptation to warm temperatures.

Global effects of forest modification on herpetofauna communities.

As the area covered by human-modified environments grows, it is increasingly important to understand the responses of communities to the novel habitats created, especially for sensitive and threatened taxa. We aimed to improve understanding of the major evolutionary and ecological processes that shape the assemblage of amphibian and reptile communities to forest modifications. To this end, we compiled a global data set of amphibian and reptile surveys in natural, disturbed (burned, logged), and transformed (monocultures, polyspecific plantations) forest communities to assess the richness, phylogenetic diversity, and composition of those communities, as well as the morphological disparity among taxa between natural and modified forest habitats. Forest transformations led to a diversity reduction of 15.46% relative to the statistically nonsignificant effect of disturbances. Transformations also led to a community composition that was 39.4% dissimilar to that on natural forests, compared with 16.1% difference in disturbances. Modifications did not affect the morphological disparity of communities (p = 0.167 and 0.744), and we found little evidence of taxon-specific responses to anthropic impacts. Monocultures and polyspecific plantations detrimentally affected the conservation and ecological value of both amphibian and reptile communities and altered the evolutionary processes shaping these communities, whereas forests with lower impact disturbances might, to some extent, serve as reservoirs of species. Although different mechanisms might buffer the collapse of herpetological communities, preserving remaining natural forests is necessary for conserving communities in the face of future anthropic pressures.

Con el aumento del área cubierta por entornos modificados por el humano, cada vez es más importante entender las respuestas que tienen las comunidades a los nuevos hábitats creados, especialmente en los taxones sensibles y amenazados. El objetivo de este estudio es mejorar el conocimiento sobre los principales procesos evolutivos y ecológicos que condicionan el ensamblado de las comunidades de anfibios y reptiles ante las modificaciones forestales. Con este fin, compilamos un conjunto de datos globales de los censos de anfibios y reptiles en las comunidades forestales naturales, perturbadas (taladas, incendiadas) y transformadas (monocultivos, plantaciones poliespecíficas) para valorar la riqueza, diversidad filogenética y composición de aquellas comunidades, así como la disparidad morfológica entre los taxones entre los hábitats forestales naturales y modificados. Las transformaciones forestales llevaron a una reducción de 15.46% de la diversidad en relación al efecto sin significancia estadística de las perturbaciones. Las transformaciones también derivaron en una composición comunitaria que fue 39.4% diferente a la de los bosques naturales, en comparación con el 16.1% de diferencia en las perturbaciones. Las modificaciones no afectaron la disparidad morfológica de las comunidades (p = 0.167 y 0.744) y no encontramos suficiente evidencia de respuestas específicas por taxón a los impactos antrópicos. Los monocultivos y las plantaciones poliespecíficas afectaron negativamente a la conservación y al valor ecológico de las comunidades de anfibios y reptiles y alteraron los procesos evolutivos que condicionan a estas comunidades, mientras que los bosques menos impactados podrían, hasta cierto punto, actuar como reservorios de especies. Sin embargo, mientras que diferentes mecanismos pueden amortiguar el colapso de las comunidades herpetológicas, se requiere la conservación de los bosques naturales para preservar las comunidades que se enfrentarán a presiones antrópicas.

Bird lineages colonizing urban habitats have diversified at high rates across deep time.

Aim: Urbanization exposes species to novel ecological conditions. Some species thrive in urban areas, whereas many others are excluded from these human-made environments. Previous analyses suggest that the ability to cope with rapid environmental change is associated with long-term patterns of diversification, but whether the suite of traits associated with the ability to colonize urban environments is linked to this process remains poorly understood. Location: World. Time period: Current. Major taxa studied: Passerine birds. Methods: We applied macroevolutionary models to a large dataset of passerine birds to compare the evolutionary history of urban-tolerant species with that of urban-avoidant species. Specifically, we examined models of state-dependent speciation and extinction to assess the macroevolution of urban tolerance as a binary trait, in addition to models of quantitative trait-dependent diversification based on relative urban abundance. We also ran simulation-based model assessments to explore potential sources of bias. Results: We provide evidence that historically, species with traits promoting urban colonization have undergone faster diversification than urban-avoidant species, indicating that urbanization favours clades with a historical tendency towards rapid speciation or reduced extinction. In addition, we find that past transitions towards states that currently impede urban colonization by passerines have been more frequent than in the opposite direction. Furthermore, we find a portion of urban-avoidant passerines to be recent and to undergo fast diversification. All highly supported models give this result consistently. Main conclusions: Urbanization is mainly associated with the loss of lineages that are inherently more vulnerable to extinction over deep time, whereas cities tend to be colonized by less vulnerable lineages, for which urbanization might be neutral or positive in terms of longer-term diversification. Urban avoidance is associated with high rates of recent diversification for some clades occurring in regions with relatively intact natural ecosystems and low current levels of urbanization.

Effects of developmental and adult environments on ageing.

Developmental and adult environments can interact in complex ways to influence the fitness of individuals. Most studies investigating effects of the environment on fitness focus on environments experienced and traits expressed at a single point in an organism's life. However, environments vary with time, so the effects of the environments that organisms experience at different ages may interact to affect how traits change throughout life. Here, we test whether thermal stress experienced during development leads individuals to cope better with thermal stress as adults. We manipulated temperature during both development and adulthood and measured a range of life-history traits, including senescence, in male and female seed beetles (Callosobruchus maculatus). We found that thermal stress during development reduced adult reproductive performance of females. In contrast, life span and age-dependent mortality were affected more by adult than developmental environments, with high adult temperatures decreasing longevity and increasing age-dependent mortality. Aside from an interaction between developmental and adult environments to affect age-dependent changes in male weight, we did not find any evidence of a beneficial acclimation response to developmental thermal stress. Overall, our results show that effects of developmental and adult environments can be both sex and trait specific, and that a full understanding of how environments interact to affect fitness and ageing requires the integrated study of conditions experienced during different stages of ontogeny.

In the shadows: wildlife behaviour in tree plantations.

Destruction of natural habitats for tree plantations is a major threat to wildlife. These novel environments elicit behavioural changes that can either be detrimental or beneficial to survival and reproduction, with population - and community - level consequences. However, compared with well-documented changes following other forms of habitat modification, we know little about wildlife behavioural responses to tree plantations, and even less about their associated fitness costs. Here, we highlight critical knowledge gaps in understanding the ecological and evolutionary consequences of behavioural shifts caused by tree plantations and discuss how wildlife responses to plantations could be critical in determining which species persist in these highly modified environments.

Best practices for building and curating databases for comparative analyses.

Comparative analyses have a long history of macro-ecological and -evolutionary approaches to understand structure, function, mechanism and constraint. As the pace of science accelerates, there is ever-increasing access to diverse types of data and open access databases that are enabling and inspiring new research. Whether conducting a species-level trait-based analysis or a formal meta-analysis of study effect sizes, comparative approaches share a common reliance on reliable, carefully curated databases. Unlike many scientific endeavors, building a database is a process that many researchers undertake infrequently and in which we are not formally trained. This Commentary provides an introduction to building databases for comparative analyses and highlights challenges and solutions that the authors of this Commentary have faced in their own experiences. We focus on four major tips: (1) carefully strategizing the literature search; (2) structuring databases for multiple use; (3) establishing version control within (and beyond) your study; and (4) the importance of making databases accessible. We highlight how one's approach to these tasks often depends on the goal of the study and the nature of the data. Finally, we assert that the curation of single-question databases has several disadvantages: it limits the possibility of using databases for multiple purposes and decreases efficiency due to independent researchers repeatedly sifting through large volumes of raw information. We argue that curating databases that are broader than one research question can provide a large return on investment, and that research fields could increase efficiency if community curation of databases was established.

The role of maternal effects on offspring performance in familiar and novel environments.

Maternal effects are an important evolutionary force that may either facilitate adaptation to a new environment or buffer against unfavourable conditions. The degree of variation in traits expressed by siblings from different mothers is often sensitive to environmental conditions. This could generate a Maternal-by-Environment interaction (M × E) that inflates estimates of Genotype-by-Environment effects (G × E). We aimed to test for environment-specific maternal effects (M × E) using a paternal full-sib/half-sib breeding design in the seed beetle Callosobruchus maculatus, where we split and reared offspring from the same mother on two different bean host types-original and novel. Our quantitative genetic analysis indicated that maternal effects were very small on both host types for all the measured life-history traits. There was also little evidence that maternal oviposition preference for a particular host type predicted her offspring's performance on that host. Further, additive genetic variance for most traits was relatively high on both hosts. While there was higher heritability for offspring reared in the novel host, there was no evidence for G × Es, and most cross-host genetic correlations were positive. This suggests that offspring from the same family ranked similarly for performance on both host types. Our results point to a genetic basis of host adaptation in the seed beetle, rather than maternal effects. Even so, we encourage researchers to test for potential M × Es because, due to a lack of testing, it remains unclear how often they arise.

The effects of competition on fitness depend on the sex of both competitors.

In intraspecific competition, the sex of competing individuals is likely to be important in determining the outcome of competitive interactions and the way exposure to conspecifics during development influences adult fitness traits. Previous studies have explored differences between males and females in their response to intraspecific competition. However, few have tested how the sex of the competitors, or any interactions between focal and competitor sex, influences the nature and intensity of competition. We set up larval seed beetles Callosobruchus maculatus to develop either alone or in the presence of a male or female competitor and measured a suite of traits: development time, emergence weight; male ejaculate mass, copulation duration, and lifespan; and female lifetime fecundity, offspring egg-adult survival, and lifespan. We found effects of competition and competitor sex on the development time and emergence weight of both males and females, and also of an interaction between focal and competitor sex: Females emerged lighter when competing with another female, while males did not. There was little effect of larval competition on male and female adult fitness traits, with the exception of the effect of a female competitor on a focal female's offspring survival rate. Our results highlight the importance of directly measuring the effects of competition on fitness traits, rather than distant proxies for fitness, and suggest that competition with the sex with the greater resource requirements (here females) might play a role in driving trait evolution. We also found that male-male competition during development resulted in shorter copulation times than male-female competition, a result that remained when controlling for the weight of competitors. Although it is difficult to definitively tease apart the effects of social environment and access to resources, this result suggests that something about the sex of competitors other than their size is driving this pattern.

Stress in the city: meta-analysis indicates no overall evidence for stress in urban vertebrates.

As cities continue to grow it is increasingly important to understand the long-term responses of wildlife to urban environments. There have been increased efforts to determine whether urbanization imposes chronic stress on wild animals, but empirical evidence is mixed. Here, we conduct a meta-analysis to test whether there is, on average, a detrimental effect of urbanization based on baseline and stress-induced glucocorticoid levels of wild vertebrates. We found no effect of urbanization on glucocorticoid levels, and none of sex, season, life stage, taxon, size of the city nor methodology accounted for variation in the observed effect sizes. At face value, our results suggest that urban areas are no more stressful for wildlife than rural or non-urban areas, but we offer a few reasons why this conclusion could be premature. We propose that refining methods of data collection will improve our understanding of how urbanization affects the health and survival of wildlife.

Combined effects of rearing and testing temperatures on sperm traits.

Temperature experienced during early development can affect a range of adult life-history traits. Animals often show seemingly adaptive developmental plasticity-with animals reared at certain temperatures performing better as adults at those temperatures. The extent to which this type of adaptive response occurs in gonadal tissue that affects sperm traits is, however, poorly studied. We initially reared male mosquito fish (Gambusia holbrooki) at either 18°C or 30°C, and then measured their sperm reserves as adults. We also looked at the velocity of their sperm, at both the matched and mismatched temperatures. Although males reared at 30°C were larger than those initially reared at 18°C, there was no detectable effect of rearing temperature on absolute sperm number. Sperm swam faster at 30°C than 18°C regardless of the male's rearing temperature. Therefore, we found no evidence of adaptive developmental plasticity. Rearing temperature did, however, significantly influence the relationship between male body size and sperm velocity. Larger males had faster sperm when reared at the warmer temperature and slower sperm when reared at the cooler temperature. This suggests that rearing temperature could alter the relationship between pre-copulatory sexual selection and post-copulatory sexual selection as male size affects mating success. Finally, there was a positive correlation between velocities at the two test temperatures, suggesting that temperature experienced during sperm competition is unlikely to affect a male's relative fertilization success.

Sex in the city: sexual selection and urban colonization in passerines.

Urbanization leads to a rapid and drastic transformation of habitats, forcing native fauna to manage novel ecological challenges or to move. Sexual selection is a powerful evolutionary force, which is sometimes predicted to enhance the ability of species to adapt to novel environments because it allows females to choose high-quality males, but other times is predicted to reduce the viability of populations because it pushes males beyond naturally selected optima. However, we do not know whether or how sexual selection contributes to the likelihood that animals will establish in urban areas. We use a comparative analysis of passerine birds to test whether traits associated with pre- and post-mating sexual selection predict successful colonization of urban areas. We found that plumage dichromatism was negatively associated with urban tolerance, but found no relationship with sexual size dimorphism or testes mass relative to body mass. While we cannot determine the exact reason why species with high plumage dichromatism occur less in cities, it is likely that urban areas increase the costs of expressing bright coloration due, for instance, to dietary constraints, limited male parental care or increased predation.

An experimental test for body size-dependent effects of male harassment and an elevated copulation rate on female lifetime fecundity and offspring performance.

Many studies investigate the benefits of polyandry, but repeated interactions with males can lower female reproductive success. Interacting with males might even decrease offspring performance if it reduces a female's ability to transfer maternal resources. Male presence can be detrimental for females in two ways: by forcing females to mate at a higher rate and through costs associated with resisting male mating attempts. Teasing apart the relative costs of elevated mating rates from those of greater male harassment is critical to understand the evolution of mating strategies. Furthermore, it is important to test whether a male's phenotype, notably body size, has differential effects on female reproductive success versus the performance of offspring, and whether this is due to male body size affecting the costs of harassment or the actual mating rate. In the eastern mosquitofish Gambusia holbrooki, males vary greatly in body size and continually attempt to inseminate females. We experimentally manipulated male presence (i.e., harassment), male body size and whether males could copulate. Exposure to males had strong detrimental effects on female reproductive output, growth and immune response, independent of male size or whether males could copulate. In contrast, there was a little evidence of a cross-generational effect of male harassment or mating rate on offspring performance. Our results suggest that females housed with males pay direct costs due to reduced condition and offspring production and that these costs are not a consequence of increased mating rates. Furthermore, exposure to males does not affect offspring reproductive traits.

Sexual selection, body mass and molecular evolution interact to predict diversification in birds.

Sexual selection is a powerful agent of evolution, driving microevolutionary changes in the genome and macroevolutionary rates of lineage diversification. The mechanisms by which sexual selection might influence macroevolution remain poorly understood. For example, sexual selection might drive positive selection for key adaptations that facilitate diversification. Furthermore, sexual selection might be a general driver of molecular evolutionary rate. We lay out some of the potential mechanisms that create a link between sexual selection and diversification, based on causal effects on other life-history traits such as body mass and the rate of molecular evolution. Birds are ideally suited for testing the importance of these relationships because of their diverse reproductive systems and the multiple evolutionary radiations that have produced their astounding modern diversity. We show that sexual selection (measured as the degree of polygyny) interacts with the rate of molecular evolution and with body mass to predict species richness at the genus level. A high degree of polygyny and rapid molecular evolution are positively associated with the net rate of diversification, with the two factors being especially important for explaining diversification in large-bodied taxa. Our findings further suggest that mutation rates underpin some of the macroevolutionary effects of sexual selection. We synthesize the existing theory on sexual selection as a force for diversity and propose avenues for exploring this association using genome data.

Eucalypt leaf litter impairs growth and development of amphibian larvae, inhibits their antipredator responses and alters their physiology.

Consequences of human actions like global warming, spread of exotic species or resource consumption are pushing species to extinction. Even species considered to be at low extinction risk often show signs of local declines. Here, we evaluate the impact of eucalypt plantations, the best-known exotic tree species worldwide and its interaction with temperature and predators on amphibian development, growth, antipredator responses and physiology. For this purpose, we applied a fully factorial experiment crossing two types of leaf litter (native oak or eucalypt), two temperatures (15 and 20°C) and presence/absence of native predators. We found that leachates of eucalypt leaf litter reduced amphibian development and growth, compromised their antipredator responses and altered their metabolic rate. Increased temperature itself also posed serious alterations on development, growth, antioxidant ability and the immune status of tadpoles. However, the combined effects of eucalypt leaf litter and increased temperature were additive, not synergistic. Therefore, we show that non-lethal levels of a globally spread disruptor such as leachates from eucalypt leaf litter can seriously impact the life history and physiology of native amphibian populations. This study highlights the need to evaluate the status of wild populations exposed to human activities even if not at an obvious immediate risk of extinction, based on reliable stress markers, in order to anticipate demographic declines that may be hard to reverse once started. Replacing eucalypt plantations with native trees in protected areas would help improving the health of local amphibian larvae. In zones of economic interest, we would recommend providing patches of native vegetation around ponds and removing eucalypt leaf litter from pond basins during their dry phase.

Increased temperature disrupts chemical communication in some species but not others: The importance of local adaptation and distribution.

Environmental conditions experienced by a species during its evolutionary history may shape the signals it uses for communication. Consequently, rapid environmental changes may lead to less effective signals, which interfere with communication between individuals, altering life history traits such as predator detection and mate searching. Increased temperature can reduce the efficacy of scent marks released by male lizards, but the extent to which this negative effect is related to specific biological traits and evolutionary histories across species and populations have not been explored. We experimentally tested how increased temperature affects the efficacy of chemical signals of high- and low-altitude populations of three lizard species that differ in their ecological requirements and altitudinal distributions. We tested the behavioral chemosensory responses of males from each species and population to male scent marks that had been incubated at one of two temperatures (cold 16°C or hot 20°C). In high-altitude populations of a mountain species (Iberolacerta monticola), the efficacy of chemical signals (i.e., latency time and number of tongue flicks) was lower after scent marks had been exposed to a hot temperature. The temperature that scent marks were incubated at did not affect the efficacy of chemical signals in a ubiquitous species (Podarcis muralis) or another mountain species (I. bonalli). Our results suggest that specific ecological traits arising through local adaptation to restricted distributions may be important in determining species vulnerability to climatic change.

Condition-dependent trade-offs between sexual traits, body condition and immunity: the effect of novel habitats.

BACKGROUND: The optimal allocation of resources to sexual signals and other life history traits is usually dependent on an individual's condition, while variation in the expression of sexual traits across environments depends on the combined effects of local adaptation, mean condition, and phenotypic responses to environment-specific cues that affect resource allocation. A clear contrast can often be drawn between natural habitats and novel habitats, such as forest plantations and urban areas. In some species, males seem to change their sexual signals in these novel environments, but why this occurs and how it affects signal reliability is still poorly understood. RESULTS: The relative size of sexual traits and level of immune responses were significantly lower for male palmate newts Lissotriton helveticus caught in pine and eucalyptus plantations compared to those caught in native forests, but there was no habitat-dependent difference in body condition (n = 18 sites, 382 males). The reliability with which sexual traits signalled body condition and immune responses was the same in all three habitats. Finally, we conducted a mesocosm experiment in which males were maintained in pine, eucalypt or oak infused water for 21 days. Males in plantation-like water (pine or eucalypt) showed significantly lower immune responses but no change in body condition. This matches the pattern seen for field-caught males. Unlike field-caught males, however, there was no relationship between water type and relative sexual trait size. CONCLUSIONS: Pine and eucalyptus plantations are likely to be detrimental to male palmate newt because they are associated with reduced immune function and smaller sexual traits. This could be because ecological aspects of these novel habitats, such as high water turbidity or changes in male-male competition, drive selection for reduced investment into sexual traits. However, it is more probable that there are differences in the ease of acquisition, hence optimal allocation, of resources among habitats. Our mesocosm experiment also provides some evidence that water toxicity is a causal factor. Our findings offer insights into how plantations affect amphibian life histories, and how novel habitats might generate long-term selection for new resource allocation strategies in native species.