Hutchinson's ecological theater and evolutionary play is a classical view of evolutionary ecology—ecology provides a template in which evolution occurs. An opposing view is that ecological and evolutionary changes are like two actors on a stage, intertwined by density and frequency dependence. These opposing views correspond to hard and soft selection, respectively. Although often presented as diametrically

How wide is the time window for introgression after divergence? Pulido‐Santacruz et al. (2020) addressed this question by studying the evolutionary history of the bird genus Dendrocincla. They found five introgression events that occurred between a few hundred thousand and around 2.5 million years after divergence. The introgressed genomic proportion declined exponentially with the age of the hybridizing

Global biodiversity currently peaks at the equator and decreases toward the poles. Growing fossil evidence suggest this hump‐shaped latitudinal diversity gradient (LDG) has not been persistent through time, with similar diversity across latitudes flattening out the LDG during past greenhouse periods. However, when and how diversity declined at high latitudes to generate the modern LDG remains an open

Coordination between nuclear and mitochondrial genomes is critical to metabolic processes underlying animals' ability to adapt to local environments, yet consequences of mitonuclear interactions have rarely been investigated in populations where individuals with divergent mitochondrial and nuclear genomes naturally interbreed. Genetic variation in the leaf beetle Chrysomela aeneicollis was assessed

Functional decoupling of oral and pharyngeal jaws is widely considered to have expanded the ecological repertoire of cichlid fishes. But, the degree to which the evolution of these jaw systems is decoupled and whether decoupling has impacted trophic diversification remains unknown. Focusing on the large Neotropical radiation of cichlids, we ask whether oral and pharyngeal jaw evolution is correlated

The study of hybrid zones can provide insight into the genetic basis of species differences that are relevant for the maintenance of reproductive isolation. Hybrid zones can also provide insight into climate change, species distributions, and evolution. The hybrid zone between black‐capped chickadees (Poecile atricapillus) and Carolina chickadees (P. carolinensis) is shifting northward in response

While 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

The within‐host evolutionary dynamics of tuberculosis (TB) remain unclear, and underlying biological characteristics render standard population genetic approaches based upon the Wright‐Fisher model largely inappropriate. In addition, the compact genome combined with an absence of recombination is expected to result in strong purifying selection effects. Thus, it is imperative to establish a biologically‐relevant

Pleiotropy between male signals and female preferences can facilitate evolution of sexual communication by maintaining coordination between the sexes. Alternatively, it can favor variation in the mating system, such as a reproductive polymorphism. It is unknown how common either of these scenarios is in nature. In Pacific field crickets (Teleogryllus oceanicus) on Kauai, Hawaii, a mutation (flatwing)

This study uses viability selection simulations to predict the evolvability of primate species based on specialization of limb morphology. Following the author's predictions, more specialized limb morphologies were less responsive to selective pressures. This led to a slower transition toward new adaptive peaks. Specifically, evolvability of primate limbs was found to be associated with the degree

Urbanization is intensifying worldwide, and while some species tolerate and even exploit urban environments, many others are excluded entirely from this new habitat. Understanding the factors that underlie tolerance of urbanization is thus of rapidly growing importance. Here, we examine urban tolerance across a diverse group of lizards: Caribbean members of the neotropical genus Anolis. Our analyses

Conflicting selection is an important evolutionary mechanism since it impedes directional evolution and helps to maintain phenotypic variation. It can arise when mutualistic and antagonistic selective agents exert opposing selection on the same trait and when distinct phenotypic optima are favored by different fitness components. In this study, we test for conflicting selection through different sexual

The rate of hybridization among taxa is a central consideration in any discussion of speciation, but rates of hybridization are difficult to estimate in most wild populations of animals. We used a successful citizen science dataset, eBird, to estimate the rates of hybridization for wild birds in the United States. We calculated the frequency at which hybrid individuals belonging to different species

What evolutionary processes shaped the genomic landscape of differentiation in Selaphorus hummingbirds? Battey (2020) shows that the islands of differentiation on the Z‐chromosome are most likely the outcome of linked selection. Furthermore, these islands might contain barrier loci that contribute to reproductive isolation between these hybridizing hummingbirds.

How do obligate parasites cope with hosts that lack genetic elements required for parasite replication? Gupta et. al. (2020) illustrate an experimental evolution system where lambda bacteriophages circumvent a defective gene network in their E. coli host (which initially made it impossible for them to replicate) through both intracellular cooperation and evolutionary changes in phage life‐history traits

In Fisher's model of sexual selection, a female preference for a male trait spreads together with the trait because their genetic bases become correlated. This can be interpreted as a “greenbeard” system: a preference gene, by inducing a female to mate with a trait‐bearing male, favors itself because the male is disproportionately likely also to carry the preference gene. Here, we use this logic to

To better predict how populations and communities respond to climatic temperature variation, it is necessary to understand how the shape of the response of fitness‐related rates to temperature evolves (the thermal performance curve). Currently, there is disagreement about the extent to which the evolution of thermal performance curves is constrained. One school of thought has argued for the prevalence

Natural selection has been studied for several decades, resulting in the computation of thousands of selection estimates. Although the importance of environmental conditions on selection has often been suggested, published estimates rarely take into account the effects of environmental heterogeneity on selection patterns. Here, we estimated linear and nonlinear viability selection gradients on morphological

Comparative phylogeographic studies often support shared divergence times for co‐distributed species with similar life histories and habitat specializations. During the late Holocene, West Africa experienced aridification and the turnover of rain forest habitats into savannas. These fragmented rain forests harbor impressive numbers of endemic and threatened species. In this setting, populations of

Environmentally transmitted parasites spend time in the abiotic environment, where they are subjected to a variety of stressors. Learning how they face this challenge is essential if we are to understand how host–parasite interactions may vary across environmental gradients. We used a zooplankton–bacteria host–parasite system where availability of sunlight (solar radiation) influences disease dynamics

Since the New Synthesis, most migration‐selection balance theory has predicted that there should be negligible differentiation over small spatial scales (relative to dispersal), because gene flow should erode any effect of divergent selection. Nevertheless, there are classic examples of microgeographic divergence, which theory suggests can arise under specific conditions: exceptionally strong selection

Sexual selection theory provides a framework for investigating the evolution of traits involved in attracting and competing for mates. Given the sexual function of such traits, studies generally focus on individual interactions (i.e., displays and contests) in explaining trait origin and persistence. We show that ecological factors can strongly influence the adaptive value of these traits, and changes

The incidence of introgression during the diversification process and the timespan following divergence when introgression is possible are poorly understood in the neotropics where high species richness could provide extensive opportunities for genetic exchange. We used thousands of genome‐wide SNPs to infer phylogenetic relationships, calculate ages of splitting, and to estimate the timing of introgression

The dorsal surfaces of many taxonomic groups often feature repetitive pattern elements consisting of stripes, spots, or bands. Here, we investigate how distinct categories of camouflage pattern work by relating them to ecological and behavioral traits in 439 species of gecko. We use phylogenetic comparative methods to test outstanding hypotheses based on camouflage theory and research in other taxa

Male genitals are highly divergent in animals with internal fertilization. Most studies attempting to explain this diversity have focused on testing the major hypotheses of genital evolution (the lock‐and‐key, pleiotropy, and sexual selection hypotheses), and quantifying the form of selection targeting male genitals has played an important role in this endeavor. However, we currently know far less

Many developmental traits that are critical to the survival of the organism are also robust. These robust traits are resistant to phenotypic change in the face of variation. This presents a challenge to evolution. In this article, we asked whether and how a well‐established robust trait, Drosophila segment patterning, changed over the evolutionary history of the genus. We compared segment position

An important driver of evolution in viruses is natural selection to optimize the use of their hosts’ genetic network. To learn how viruses respond to this pressure, we disrupted the genetic network of Escherichia coli to inhibit replication of its virus, bacteriophage lambda, and then observed how λ evolved to compensate. We deleted E. coli's dnaJ gene, which lambda uses to initiate DNA replication

Primate limb morphology is often described as either generalized, that is, suited to a range of locomotor and positional behaviors, or specialized for unique locomotor behaviors such as brachiation or bipedalism. The evolution of highly specialized limb morphology may result in loss of evolvability, that is, in a decreased capacity of the locomotor skeleton to evolve in response to selection towards

Levels of genetic differentiation vary widely along the genomes of recently diverged species. What processes cause this variation? Here, I analyze geographic population structure and genome‐wide patterns of variation in the Rufous, Allen's, and Calliope Hummingbirds (Selasphorus rufus/Selasphorus sasin/Selasphorus calliope) and assess evidence that linked selection on the Z chromosome drives patterns

Many animal species across different taxa change their habitat during their development. An ontogenetic habitat shift enables the development of early vulnerable‐to‐predation stages in a safe ‘nursery’ habitat with reduced predation mortality, while less vulnerable stages can exploit a more risky, rich feeding habitat. Therefore, the timing of the habitat shift is crucial for individual fitness. We

Macroclimatic niches are indirect and potentially inadequate predictors of the realized environmental conditions that many species experience. Consequently, analyses of niche evolution based on macroclimatic data alone may incompletely represent the evolutionary dynamics of species niches. Yet, understanding how an organisms’ climatic (Grinnellian) niche responds to changing macroclimatic conditions

Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of non‐random mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focuses on self‐fertilization and its consequences for

A classic hypothesis posits that lineages exhibiting long‐term stasis are broadly adapted generalists that remain well‐adapted despite environmental change. However, lacking constraints that steepen adaptive peaks and stabilize the optimum, generalists’ phenotypes might drift around a broad adaptive plateau. We propose that stasis would be likely for morphological specialists that behave as ecological

Cave adaptation has evolved repeatedly across the Tree of Life, famously leading to pigmentation and eye degeneration and loss, yet its macroevolutionary implications remain poorly understood. We use the North American amblyopsid fishes, a family spanning a wide degree of cave adaptation, to examine the impact of cave specialization on the modes and tempo of evolution. We reconstruct evolutionary relationships

A pattern of population structure called isolation‐by‐environment (IBE) evolves when gene flow connecting populations in different habitats is lower than expected. Although IBE is widespread, there is limited information on its magnitude compared with other factors influencing gene flow. We estimated the relative importance of IBE in the frog Rana temporaria in the Swiss Alps, a geographic context

Communication signals serve crucial survival and reproductive functions. In Gabon, the widely distributed mormyrid fish Paramormyrops kingsleyae emits an electric organ discharge (EOD) signal with a dual role in communication and electrolocation that exhibits remarkable variation: populations of P. kingsleyae have either biphasic or triphasic EODs, a feature which characterizes interspecific signal

Comparing divergences across multiple sister population‐pairs has been a focus in phylogeography since its inception. Initial approaches utilized organelle genetic data and involved qualitative comparisons of phylogenetic patterns to evaluate hypotheses of shared and variable evolutionary responses. This endeavor has progressed with coalescent model‐based statistical techniques and advances in next‐generation

Sex is determined by chromosomes in mammals but it can be influenced by the environment in many worms, crustaceans, and vertebrates. Despite this, there is little understanding of the relationship between ecology and the evolution of sexual systems. The nematode Auanema freiburgensis has a unique sex determination system in which individuals carrying one X chromosome develop into males while XX individuals

Male hummingbirds have repeatedly evolved sexually dimorphic tails that they use as ornaments during courtship. We examine how male ornament evolution is reflected in female morphology. Lande's two‐step model of the evolution of dimorphism predicts that γ (the genetic correlation between the sexes) causes trait elaboration to first evolve quickly in both sexes, then dimorphism evolves more slowly.

Why do females of socially monogamous species engage in extra‐pair copulations? This long‐standing question remains a puzzle, because the benefits of female promiscuous behavior often do not seem to outweigh the costs. Genetic constraint models offer an answer by proposing that female promiscuity emerges through selection favoring alleles that are either beneficial for male reproductive success (intersexual

Adaptive explanations for the evolution of extra‐pair paternity (EPP) suggest that females seek extra‐pair copulations with high quality males. Still, the link between ornamentation, individual quality, and paternity remains unclear. Moreover, honest signaling is essential when explaining EPP because it is needed for sexual selection to occur; yet, it is understudied in multiple ornaments. Because

Abiotic stress is a major force of selection that organisms are constantly facing. While the evolutionary effects of various stressors have been broadly studied, it is only more recently that the relevance of interactions between evolution and underlying ecological conditions, that is, eco‐evolutionary feedbacks, have been highlighted. Here, we experimentally investigated how populations adapt to pH‐stress

Most flowering plants are hermaphroditic and experience strong pressures to evolve self‐pollination (automatic selection and reproductive assurance). Inbreeding depression (ID) can oppose selection for selfing, but it remains unclear if ID is typically strong enough to maintain outcrossing. To measure the full cost of sustained inbreeding on fitness, and its genomic basis, we planted highly homozygous

Understanding the mechanisms of adaptive population differentiation requires that both the functional and adaptive significance of divergent traits are characterized in contrasting environments. Here, we (a) determined the effects of floral spur length on pollen removal and receipt using plants with artificial spurs representing the species‐wide variation in length, and (b) quantified pollinator‐mediated

Ecological specialization is a central driver of adaptive evolution. However, selective pressures may uniquely affect different ecomorphological traits (e.g., size and shape), complicating efforts to investigate the role of ecology in generating phenotypic diversity. Comparative studies can help remedy this issue by identifying specific relationships between ecologies and morphologies, thus elucidating

Ecological specialization is an important engine of evolutionary change and adaptive radiation, but empirical evidence of local adaptation in marine environments is rare, a pattern that has been attributed to the high dispersal ability of marine taxa and limited geographic barriers to gene flow. The broad‐nosed pipefish, Syngnathus typhle, is one of the most broadly distributed syngnathid species and

Sex chromosomes in vertebrates range from highly heteromorphic (as in most birds and mammals) to strictly homomorphic (as in many fishes, amphibians, and nonavian reptiles). Reasons for these contrasted evolutionary trajectories remain unclear, but species such as common frogs with polymorphism in the extent of sex chromosome differentiation may potentially deliver important clues. By investigating

Most of the theory for the evolution of caste specialization in social insects assumes that increased efficiency in worker labor leads to specialization and increased worker efficiency gives colonies with behavioral specialists an advantage. However, there are an increasing number of studies that show that the task specialists within social insect colonies do not have the highest efficiency. Indeed

Understanding how selective forces influence patterns of symmetry remains an active area of research in evolutionary biology. One hypothesis, which has received relatively little attention, suggests that the functional importance of morphological characters may influence patterns of symmetry. Specifically, it posits that for structures that display bilateral symmetry, those with greater functional

Closely related species that occur across steep environmental gradients often display clear body size differences, and examining this pattern is crucial to understanding how environmental variation shapes diversity. Australian endemic rodents in the Pseudomys Division (Muridae: Murinae) have repeatedly colonized the arid, monsoon, and mesic biomes over the last 5 million years. Using occurrence records

Why are female birds ornamented? In a comparative phylogenetic study of hummingbirds (Trochilidae), Clark and Rankin tackled this crucial question and investigated how male tail evolution is reflected in female morphology.

Outcrossing is maintained in many hermaphroditic species despite theoretical work suggesting that alleles increasing selfing should invade outcrossing populations. Brown and Kelly (2019) identify reasons why this may not have occurred in an outcrossing population of monkeyflower, namely that inbreeding depression causes strong reductions in fitness, resulting in selection for the maintenance of outcrossing

In systems with early stage sex‐chromosome evolution, climate gradients can largely explain changes in the sex‐determining systems (i.e., genetic or environmental factors). However, in the common frog Rana temporaria, Phillips et al. found that phylogeography, rather than elevation (used as a proxy for climate), was associated with homomorphic sex‐chromosome differentiation levels.

Biome shifts are thought to be relatively rare, but some clades shift among starkly different environments with relative ease. What causes these shifts, and how do they shape phenotypic evolution? Roycroft et al. found that biome shifts in the Pseudomys Division of murid rodents were repeatedly accompanied by body size evolution in accordance with Bergmann's rule, suggesting adaptive evolution in response

Morales et al. test predictions of adaptive radiation theory and phenotypic convergence in Myotis bats using genomic target capture and a morphological dataset that represents 80% of the species described for this genus. The authors demonstrate that ecomorphological convergence has occurred multiple times throughout the history of Myotis, despite finding no diversification rate shifts associated with

This multi-day exercise is designed for a college Genetics and Evolution laboratory to demonstrate concepts of inheritance and phenotypic and molecular evolution using a live model organism, Drosophila simulans. Students set up an experimental fruit fly population consisting of ten white eyed flies and one red eyed fly. Having red eyes is advantageous compared to having white eyes, allowing students

There is no place on Earth like the Galapagos Islands and no better destination to discuss the reality of evolution. Under the theme 'Why Does Evolution Matter', the University San Francisco of Quito (USFQ), Ecuador, and its Galapagos Institute for the Arts and Sciences (GAIAS), organized the III World Evolution Summit in San Cristóbal Island. The 200-attendee meeting took place on 1 to 5 June 2013;

Even students who reject evolution are often willing to consider cases in which evolutionary biology contributes to, or undermines, biomedical interventions. Moreover the intersection of evolutionary biology and biomedicine is fascinating in its own right. This review offers an overview of the ways in which evolution has impacted the design and deployment of live-attenuated virus vaccines, with subsections

Acceptance of evolution by educators of prospective teachers remains superficially studied despite their role in having mentored schoolteachers whose weak support of evolution is known. Here, we contrast the views of New England educators of prospective teachers (n=62; 87% Ph. D./doctorate holders in 32 specializations) with those of the general faculty (n=244; 93% Ph.D./doctorate holders in 40 disciplines)

Public health courses are emerging as popular undergraduate offerings, especially at universities with schools of public health. It is important to note that evolution has shaped the burden of disease in the modern world in which we practice and educate for public health. Human cultures and technologies have modified life on Planet Earth and have co-evolved with myriad other species, including microorganisms