Dispersal syndromes are often defined by reference to fruit traits that are associated with distinct frugivore guilds. Studies rarely examine the relationship between seed traits and frugivores or test the alternative hypothesis that traits are shaped by climatic variables. We assess whether the evolution of seed size and physical defense are correlated with dispersal‐related traits and climatic variables

In the context of social evolution, the ecological drivers of selection are the phenotypes of other individuals. The social environment can thus evolve, potentially changing the adaptive value for different social strategies. Different branches of evolutionary biology have traditionally focused on different aspects of these feedbacks. Here, we synthesize behavioural ecology theory concerning evolutionarily

Elaborate sexually selected ornaments and armaments are costly but increase the reproductive success of their bearers (usually males). It has been postulated that high‐quality males can invest disproportionately more in such traits, making those traits honest signals of genetic quality. However, genes associated with such traits may have sexually antagonistic effects on fitness. Here, using a bulb

Organisms are exposed to environmental and mutational effects influencing both mean and variance of phenotypes. Potentially deleterious effects arising from this variation can be reduced by the evolution of buffering (canalizing) mechanisms, ultimately reducing phenotypic variability. There has been interest regarding the conditions enabling the evolution of canalization. Under some models, the circumstances

Factors that influence the distribution, abundance, and diversification of species can simultaneously affect multiple evolutionary lineages within or across communities. These include changes to the environment or inter‐specific ecological interactions that cause ranges of multiple species to contract, expand, or fragment. Such processes predict temporally clustered evolutionary events across species

The rachises of extant feathers, composed of dense cortex and spongy internal medulla, are flexible and light, yet stiff enough to withstand the load required for flight, among other functions. Incomplete knowledge of early feathers prevents a full understanding of how cylindrical rachises have evolved. Bizarre feathers with unusually wide and flattened rachises, known as “rachis‐dominated feathers”

Sexually selected ornaments are highly variable and the factors that drive variation in ornament expression are not always clear. Rare instances of female‐specific ornament evolution (such as in some dance fly species) are particularly puzzling. While some evidence suggests that such rare instances represent straightforward reversals of sexual selection intensity, the distinct nature of trade‐offs

Understanding the interplay between genetic differentiation, ancestral plasticity, and the evolution of plasticity during adaptation to environmental variation is critical to predict populations’ responses to environmental change. However, the role of plasticity in rapid adaptation in nature remains poorly understood. We here use the invasion of the horned beetle Onthophagus taurus in the United States

Allometric trends in the degree of sexual dimorphism with body size have long fascinated evolutionary biologists. Many male‐biased clades display more prominent sexual dimorphism in larger taxa (Rensch's rule), with most examples documenting this pattern for body size dimorphism. Although sexual dimorphism in traits other than body size is equally functionally relevant, characterizing allometric patterns

Conspicuous female coloration can evolve through male mate choice or via female‐female competition thereby increasing female mating success. However, when mating is not beneficial, such as in pre‐reproductive females, selection should favor cryptic rather than conspicuous coloration to avoid male detection and the associated harassment. Nevertheless, conspicuous female coloration occurs in many prereproductive

Experimental and theoretical studies have highlighted the impact of gene flow on the probability of evolutionary rescue in structured habitats. Mathematical modeling and simulations of evolutionary rescue in spatially or otherwise structured populations showed that intermediate migration rates can often maximize the probability of rescue in gradually or abruptly deteriorating habitats. These theoretical

Many closely related populations are distinguished by variation in sexual signals and this variation is hypothesized to play an important role in reproductive isolation and speciation. Within populations, there is considerable evidence that sexual signals provide information about the incidence and severity of parasite infections, but it remains unclear if variation in parasite communities across space

Saurischian dinosaurs evolved seven orders of magnitude in body mass, as well as a wide diversity of hip joint morphology and locomotor postures. The very largest saurischians possess incongruent bony hip joints, suggesting that large volumes of soft tissues mediated hip articulation. To understand the evolutionary trends and functional relationships between body size and hip anatomy of saurischians

The formation of new species via the accumulation of incompatible genetic changes is thought to result either from ecologically based divergent natural selection or the order by which mutations happen to arise, leading to different evolutionary trajectories even under similar selection pressures. There is growing evidence in support of both ecological speciation and mutation‐order speciation, but how

Do frog limb shapes reflect microhabitat use against the backdrop of shared ancestry, body size variation, and developmental constraints? Stepanova and Womack found that when phylogeny and body size are controlled, microhabitat use is a key factor in explaining anuran limb evolution. The shape of distal limb elements in anuran limbs also evolves at a higher rate than proximal elements, suggesting that

As a dispersive lineage expands its distribution across a heterogeneous landscape, it leaves behind allopatric populations with varying degrees of geographic isolation that often differentiate rapidly. In the case of oceanic islands, even narrowly separated populations often differentiate, which seems contrary to the highly dispersive nature of the founding lineage. This pattern of highly dispersive

Although metamorphosis is widespread in the animal kingdom, several species have evolved life‐cycle modifications to avoid complete metamorphosis. Some species, for example, many salamanders and newts, have deleted the adult stage via a process called paedomorphosis. Others, for example, some frog species and marine invertebrates, no longer have a distinct larval stage and reach maturation via direct

Evolutionary rescue can prevent populations from declining under climate change, and should be more likely at high‐latitude, “leading” edges of species’ ranges due to greater temperature anomalies and gene flow from warm‐adapted populations. Using a resurrection study with seeds collected before and after a 7‐year period of record warming, we tested for thermal adaptation in the scarlet monkeyflower

Many animals breed exclusively in plants that accumulate rainwater (phytotelma; e.g., bromeliad, bamboo, fruit husk, and tree hole), to which they are either physiologically or behaviorally specialized for this microhabitat. Of the numerous life‐history modes observed in frogs, few are as striking or potentially consequential as the transition from pond‐ or stream‐breeding to the deposition of eggs

There is no general explanation for why species have restricted geographic distributions. One hypothesis posits that range expansion or increasing scarcity of suitable habitat results in accumulation of mutational load due to enhanced genetic drift, which constrains population performance toward range limits and further expansion. We tested this hypothesis in the North American plant, Arabidopsis lyrata

Do mitonuclear interactions impact life history traits? Rank et al. found that these genomic interactions are of great importance in wild populations of the leaf beetle Chrysomela aeneicollis and may explain why populations are highly differentiated.

Connecting the selective forces that drive the evolution of phenotypes to their underlying genotypes is key to understanding adaptation, but such connections are rarely tested experimentally. Threespine stickleback (Gasterosteus aculeatus ) are a powerful model for such tests because genotypes that underlie putatively adaptive traits have been identified. For example, a regulatory mutation in the Ectodysplasin

As species richness varies along the tree of life, there is a great interest in identifying factors that affect the rates by which lineages speciate or go extinct. To this end, theoretical biologists have developed a suite of phylogenetic comparative methods that aim to identify where shifts in diversification rates had occurred along a phylogeny and whether they are associated with some traits. Using

Accurately estimating genetic variance components is important for studying evolution in the wild. Empirical work on domesticated and wild outbred populations suggests that dominance genetic variance represents a substantial part of genetic variance, and theoretical work predicts that ignoring dominance can inflate estimates of additive genetic variance. Whether this issue is pervasive in natural systems

A growing number of empirical studies have quantified the degree to which evolution is geometrically parallel by estimating and interpreting pairwise angles between multiple replicate lineages’ evolutionary change vectors in multivariate trait space. Similar comparisons, of distance in trait space, are used to assess the degree of convergence. These approaches amount to element‐by‐element interpretation

Male genitalia are among the most phenotypically diverse morphological traits, and sexual selection is widely accepted as being responsible for their evolutionary divergence. Studies of house mice suggest that the shape of the baculum (penis bone) affects male reproductive fitness and experimentally imposed postmating sexual selection has been shown to drive divergence in baculum shape across generations

In temperate climates, the recurring seasonal exigencies of winter represent a fundamental physiological challenge for a wide range of organisms. In response, many temperate insects enter diapause, an alternative developmental program, including developmental arrest, that allows organisms to synchronize their life cycle with seasonal environmental variation. Geographic variation in diapause phenology

Switches in pollinators have been argued to be key drivers of floral evolution in angiosperms. However, few studies have tested the relationship between floral shape evolution and switches in pollination in large clades. In concert with a dated phylogeny, we present a morphometric analysis of corolla, anther connective, and style shape across 44% of nearly 1000 species of Salvia (Lamiaceae) and test

The adaptation of populations to changing conditions may be affected by interactions between individuals. For example, when cooperative interactions increase fecundity, they may allow populations to maintain high densities and thus keep track of moving environmental optima. Simultaneously, changes in population density alter the marginal benefits of cooperative investments, creating a feedback loop

When divergent populations are connected by gene flow, the establishment of complete reproductive isolation usually requires the joint action of multiple barrier effects. One example where multiple barrier effects are coupled consists of a single trait that is under divergent natural selection and also mediates assortative mating. Such multiple‐effect traits can strongly reduce gene flow. However,

Cold tolerance, the ability to cope with low temperature stress, is a critical adaptation in thermally variable environments. An individual's cold tolerance comprises several traits including minimum temperatures for growth and activity, ability to survive severe cold, and ability to resume normal function after cold subsides. Across species, these traits are correlated, suggesting they were shaped

Evolution should render individuals resistant to stress and particularly to stress experienced by ancestors. However, many studies report negative effects of stress experienced by one generation on the performance of subsequent generations. To assess the strength of such transgenerational effects we propose a strategy aimed at overcoming the problem of type I errors when testing multiple proxies of

Maternal effects, either environmental or genetic in origin, are an underappreciated source of phenotypic variance in natural populations. Maternal genetic effects have the potential to constrain or enhance the evolution of offspring traits depending on their magnitude and their genetic correlation with direct genetic effects. We estimated the maternal effect variance and its genetic component for

Innovations in foraging behavior can drive morphological diversity by opening up new ways of interacting with the environment, or limit diversity through functional constraints associated with different foraging behaviors. Several classic examples of adaptive radiations in birds show increased variation in ecologically relevant traits. However, these cases primarily focus on geographically narrow adaptive

Landscape genomics studies focus on identifying candidate genes under selection via spatial variation in abiotic environmental variables, but rarely by biotic factors (i.e., disease). The Tasmanian devil (Sarcophilus harrisii ) is found only on the environmentally heterogeneous island of Tasmania and is threatened with extinction by a transmissible cancer, devil facial tumor disease (DFTD). Devils

Female mate preference for males displaying costly traits is a puzzling phenomenon found in nature. Fisher was the first to propose a formal model describing this paradoxical system of sexual selection. Despite the many models constructed from his theory, much remains unknown about its mechanics, especially in different genetic settings. Through simulations, Veller et al. (2020) compared population

Many cells in the thorax of Drosophila were found to stall during replication, a phenomenon known as underreplication. Unlike underreplication in nuclei of salivary and follicle cells, this stall occurs with less than one complete round of replication. This stall point allows precise estimations of early‐replicating euchromatin and late‐replicating heterochromatin regions, providing a powerful tool

A handful of studies have investigated sexually antagonistic constraints on achieving sex‐specific fitness optima, although exclusively through male‐genome‐limited evolution experiments. In this article, we established a female‐limited X chromosome evolution experiment, where we used an X chromosome balancer to enforce the inheritance of the X through the matriline, thus removing exposure to male selective

Earth's temperature is increasing due to anthropogenic CO2 emissions; and organisms need either to adapt to higher temperatures, migrate into colder areas, or face extinction. Temperature affects nearly all aspects of an organism's physiology via its influence on metabolic rate and protein structure, therefore genetic adaptation to increased temperature may be much harder to achieve compared to other

Humans have, and continue to, dramatically influence the life history of many taxa. Identification of traits that allow taxa to tolerate humans and urban environments is important for informed conservation policy. Winchell et al. (2020) uses a phylogenetic comparative framework to identify such traits in the Caribbean clade of Anolis lizards. They provide an example of how to use disparate data sources

How does environmental heterogeneity affect natural selection on tree swallow nestlings? Houle et al. (2020) show that more precipitation and higher temperatures result in stronger selection on body mass and wing length and that agricultural intensity can affect the direction of selection. These findings raise the question of how genetic diversity changes under strong selection pressures, which will

Pleiotropy (multiple phenotypic effects of single genes) and epistasis (gene interaction) have key roles in the development of complex phenotypes, especially in polymorphic taxa. The development of discrete and heritable phenotypic polymorphisms often emerges from major‐effect genes that interact with other loci and have pleiotropic effects on multiple traits. We quantified gene expression changes

Rates of climatic niche evolution vary widely across the tree of life and are strongly associated with rates of diversification among clades. However, why the climatic niche evolves more rapidly in some clades than others remains unclear. Variation in life history traits often plays a key role in determining the environmental conditions under which species can survive, and therefore, could impact the

Although the evolution and diversification of flowers is often attributed to pollinator-mediated selection, interactions between co-occurring plant species can alter patterns of selection mediated by pollinators and other agents. The extent to which both floral density and congeneric species richness affect patterns of net and pollinator-mediated selection on multiple co-occurring species in a community

Geographical distribution of color phenotypes and associations with ecological predictors remains poorly understood. An important geographic pattern concerning this topic is Gloger's rule, which predicts the increase of pigmentation in endothermic animals from cold and dry to warm and wet environments. Didelphid marsupials exhibit a variety of color patterns, ranging from light and dark uniform to

Hybrid zones provide insights into the evolution of reproductive isolation. Sexual selection can contribute to the evolution of reproductive barriers, but it remains poorly understood how sexual traits impact gene flow in secondary contact. Here, we show that a recently evolved suite of sexual traits that function in male-male competition mediates gene flow between two lineages of wall lizards (Podarcis

Within-population variation in the traits underpinning reproductive output has long been of central interest to biologists. Since they are strongly linked to lifetime reproductive success, these traits are expected to be subject to strong selection and, if heritable, to evolve. Despite the formation of durable pair bonds in many animal taxa, reproductive traits are often regarded as female-specific

Group selection models combine selection pressure at the individual level with selection pressure at the group level. Cooperation can be costly for individuals, but beneficial for the group, and therefore, if individuals are sufficiently much assorted, and cooperators find themselves in groups with disproportionately many other cooperators, cooperation can evolve. The existing literature on group selection

Inbreeding depression resulting from partially recessive deleterious alleles is thought to be the main genetic factor preventing self-fertilizing mutants from spreading in outcrossing hermaphroditic populations. However, deleterious alleles may also generate an advantage to selfers in terms of more efficient purging, while the effects of epistasis among those alleles on inbreeding depression and mating

Do developmentally robust phenotypes evolve over the evolutionary history of a genus, and if so, how? Kalay et al. (2020) found that segmentation along the head to tail axis, a robust phenotype, has evolved in Drosophila over the evolutionary history of the genus, primarily through many small changes. This article is protected by copyright. All rights reserved.

Phenotypes respond to environments experienced directly by an individual, via phenotypic plasticity, or to the environment experienced by ancestors, via transgenerational environmental effects. The adaptive value of environmental effects depends not only on the strength and direction of the induced response but also on how long the response persists within and across generations, and how stably it

Is variation in geckos’ dorsal color patterns linked to specific camouflage strategies? In this article, Allen et al. investigate correlations at the interspecific level between color patterns and ecological traits, such as habitat or activity time, in 439 species of geckos.

All known vertebrate clones have originated from hybridization events and some have produced distinct evolutionary lineages via hybrid speciation. Amazon mollies (Poecilia formosa ) present an excellent study system to investigate how clonal species have adapted to heterogeneous environments because they are the product of a single hybridization event between male sailfin mollies (Poecilia latipinna

Forced copulation is an extreme form of sexual aggression that can affect the evolution of sex‐specific anatomy, morphology, and behavior. To characterize mechanistic and evolutionary aspects of forced copulation, we artificially selected male fruit flies based on their ability to succeed in the naturally prevalent behavior of forced matings with newly eclosed (teneral) females. The low and high forced

Species can evolve diverse strategies to survive periods of uncertainty. Animals may either invest in energy storage, allowing them to decrease foraging costs, such as locomotion or risk of predation, or they may invest in better cognitive abilities helping them to flexibly adapt their behaviour to meet novel challenges. Here we test this idea of a fat-brain trade-off in 38 species of Chinese anurans

The evolution of sexual traits often involves correlated changes in morphology and behavior. For example, in Drosophila , divergent mating displays are often accompanied by divergent pigment patterns. To better understand how such traits co‐evolve, we investigated the genetic basis of correlated divergence in wing pigmentation and mating display between the sibling species Drosophila elegans and Drosophila

Hybridization among different bird species is relatively common, but the hybridization rate of individuals is not well known. Justyn et al. use data from the citizen science project eBird to assess the individual hybridization rate in birds, showing that 0.064% of individuals are hybrids. The accuracy of this new estimate is affected by potential biases introduced by birdwatchers, such as over‐reporting

Tetrapod limbs have been used as a model system to investigate how selective pressures and constraints shape morphological evolution. Anurans have had many independent transitions to various microhabitats, allowing us to dissect how these factors influence limb morphology. Furthermore, anurans provide a unique system to test the generality of developmental constraints proposed in mammals, namely that

The diversity and the motor performance of birdsongs can both be sexually selected. In wood warblers, most species with high motor performance sing a greater proportion of trills, presumably to advertise performance, and thus have lower syllable diversity. We tested if this trade‐off between motor performance and syllable diversity extends to canaries, goldfinches and allies, a clade with much longer

Traditionally focused on Amazonian and Atlantic rainforests, studies on the origins of high Neotropical biodiversity have recently shifted to also investigate biodiversity processes in the South American dry diagonal, encompassing Chaco, Cerrado savannas, and Caatinga seasonally dry tropical forests. The plateau/depression hypothesis states that riparian forests in the Brazilian Shield in central Brazil