Evolution最新文献

Theory predicts that selection against maladaptive hybridization leads to divergence of sexual characters in co-occurring closely related species. Consequently, signal disparity should be greater between sympatric versus allopatric lineage pairs. However, this pattern may also result from species sorting or the greater evolutionary age of sympatric pairs. We used species pairs comparisons to examine the existence of acoustic divergence in a Neotropical montane radiation, the Rhinocryptidae, whose members tend to occupy different elevational ranges. Most rhinocryptids exhibit conservative morphology and are only differentiated by song attributes. Our results show that sympatric species pairs that overlap in elevation exhibited overall greater song divergence compared to allopatric species pairs after controlling for morphological differences, age and phylogenetic effects. Song divergence decreased when excluding sympatric pairs that do not overlap in elevation, suggesting that selection for improved species identification between co-occurring (syntopic) species accentuates signal differentiation. Comparative evolutionary models of signal differentiation over time revealed a similar pattern which suggests that sexual selection in syntopy might have driven reproductive character displacement in this radiation. We conclude that selection against the production of unfit hybrids could favor acoustic traits that reliably signal species identity in tropical environments where many taxa are poorly differentiated by visual attributes.

Understanding evolutionary rescue mechanisms in fragmented populations is crucial in the context of rapidly changing environments. This study employs analytical derivations and simulations within a two-deme metapopulation model using Fisher's geometric model (FGM) framework. We explore the impacts of abrupt environmental changes on two subpopulations that lead to distinct phe- notypic optima. We determine the probability density of distances between these optima through analytical derivations. This enables us to calculate the inter- section volume of the rescue domains of two subpopulations in the phenotypic space. This approach also allows us to assess the fixation probability of muta- tions that concurrently rescue both subpopulations and identify the domain of one-step rescue mutations. Our findings reveal that the likelihood of joint evolu- tionary rescue diminishes with increasing dimensionality of the phenotypic space, posing significant challenges for species with complex trait configurations. The study underscores the importance of genetic variation due to de novo mutations, local adaptation, and migration rates. These insights enhance our understanding of the factors that govern the adaptive potential of fragmented populations in response to severe environmental disturbances.

Many organisms live in predictable environments with periodic variation in growth condition. Adaptation to these conditions can lead to loss of nonessential functions, which could be maladaptive in new environments. Alternatively, living in a predictable environment can allow populations to accumulate cryptic genetic variation that may have no fitness benefit in that condition, but can facilitate adaptation to new environments. However, how these processes together shape fitness of populations growing in predictable environments remains unclear. Through laboratory evolution experiments in yeast, we show that populations grown in a nutrient-rich environment for 1000 generations generally have reduced fitness and lower adaptability to novel stressful environments. These populations showed metabolic remodeling and increased lipid accumulation in rich medium which seemed to provide osmotic protection in salt stress. Subsequent adaptation to stressors was primarily driven by de novo mutations, with very little contribution from the mutations accumulated prior to the exposure. Thus, our work suggests that without exposure to new environments, populations might lose their ability to respond effectively to these environments. Further, our findings highlight a major role of exaptation and de novo mutations in adaptation to new environments, but do not reveal a significant contribution of cryptic variation in this process.

In species with separate sexes, selection on males causes evolutionary change in female traits values (and vice versa) via genetic correlations, which has far-reaching consequences for adaptation. Here, we utilise a sex-specific form of Robertson's Secondary Theorem of Natural Selection to estimate the expected response to selection for 474 organismal-level traits and ~28,000 gene expression traits measured in the Drosophila Genetic Reference Panel (DGRP). Across organismal-level traits, selection acting on males produced a larger predicted evolutionary response than did selection acting on females, even for female traits; while for transcriptome traits selection on each sex produced a roughly equal average evolutionary response. For most traits, selection on males and females was predicted to move average trait values in the same direction, though for some traits, selection on one sex increased trait values while selection on the other sex decreased them, implying intralocus sexual conflict. Our results provide support for the hypothesis that males experience stronger selection than females, potentially accelerating adaptation in females. Furthermore, sex-opposite responses to selection appear to exist for only a small proportion of traits, consistent with observations that the inter-sex genetic correlation for fitness is positive but less than one in most populations so far studied.

The prevalence and strength of antibiotic resistance has led to an ongoing battle between the development of new treatments and the evolution of resistance. Combining multiple drugs simultaneously is a potential solution for combating antibiotic resistance. However, this approach introduces new factors that must be considered, including the influence of drug interactions on the rate of resistance evolution. When antibiotics are used in combination, their effects can be additive, synergistic, or antagonistic. In this study, we investigated the effect of higher-order interactions involving three drugs on resistance evolution in Staphylococcus epidermidis. Previous studies have shown that synergistic interactions can increase the adaptation rate. However, the effects of higher-order interactions on rates of adaptation are unclear. We investigated the adaptation of Staphylococcus epidermidis to single-, two-, and three-drug environments to assess how interactions within drug combinations influence the rate of adaptation. We analyzed both the overall interaction and emergent interaction, the latter being a unique interaction that occurs in three-drug combinations due to the presence of all three drugs, rather than simply strong pairwise interactions. Our results show that neither the overall interactions nor the emergent interactions affect adaptation rates.

How do water regime and herbivory shape phenotypic variation in plants along environmental gradients? Using a multifactorial field common garden approach, Jameel et al. (2024) showed that water availability and herbivore abundance influence the expression of foliar and reproductive traits in the perennial forb Boechera stricta. The concordance between phenotypic plasticity, phenotypic clines, and the direction of selection demonstrates the adaptive nature of plasticity in ecologically relevant traits. Furthermore, the experimental manipulations highlight which agents of selection drive the evolution of these traits.

Endosymbiotic reproductive manipulators are widely studied as sources of postzygotic isolation in arthropods, but their effect on prezygotic isolation between genetically differentiated populations has garnered less attention. We tested this using two partially isolated populations of the red and green color forms of Tetranychus urticae, either uninfected or infected with different Wolbachia strains, one inducing cytoplasmic incompatibility and the other not. We first investigated male and female preferences and found that, in absence of infection, females were not choosy, but all males preferred red-form females. Wolbachia effects were more subtle, with only the cytoplasmic incompatibility-inducing strain slightly strengthening color-form-based preferences. We then performed a double-mating experiment to test how incompatible matings affect subsequent mating behavior and offspring production as compared to compatible matings. Females mated with an incompatible male (infected and/or heterotypic) were more attractive and/or receptive to subsequent (compatible) matings, although analyses of offspring production revealed no clear benefit for this remating behavior (i.e., apparently unaltered first male sperm precedence). Finally, by computing the relative contributions of each reproductive barrier to total isolation, we showed that premating isolation matches both host-associated and Wolbachia-induced postmating isolation, suggesting that Wolbachia could contribute to reproductive isolation in this system.

During their radiation, certain groups of animals evolved significant phenotypic disparity (morphological diversity), enabling them to thrive in diverse environments. Adaptations to the same type of environment can lead to convergent evolution in function and morphology. However, well-documented examples in repeated adaptations of teleost fishes to different habitats, which are not primarily related to trophic specialization, are still scarce. Gobies are a remarkable fish group, exhibiting a great species diversity, morphological variability, and extraordinary ability to colonize very different environments. A variety of lifestyles and body forms evolved also in European lineages of gobies. We conducted two-dimensional geometric morphometric and phylomorphospace analyses in European lineages of gobies and evaluated the extent of convergent evolution in shape associated with adaptation to various habitats. Our analyses revealed the change in shape along the nektonic-cryptobenthic axis, from very slender head and body to stout body and wide head. We showed convergent evolution related to mode of locomotion in the given habitat in four ecological groups: nektonic, hyperbenthic, cryptobenthic, and freshwater gobies. Gobies, therefore, emerge as a highly diversified lineage with unique lifestyle variations, offering invaluable insights into filling of ecomorphological space and mechanisms of adaptation to various aquatic environments with distinct locomotion requirements.

Hybrid zones provide valuable opportunities to interrogate the processes that drive speciation. In a new study, Hardy et al. (2025) demonstrate that the dominant vegetation type in patchy cordgrass salt marshes and mangrove swamps drives a mosaic hybrid zone between two species of killifish. Furthermore, the authors showed that hybridization is asymmetrical, and that Fundulus grandis is more likely to hybridize than F. heteroclitus. This study highlights the need for interdisciplinary study of the environmental context of reproductive isolation.

Evolutionary theorists have emphasized for over half a century that population sampling must be conducted at the intergenerational boundary if the distinct effects of selection and inheritance are to be reliably quantified, with individuals recognized at the point of conception and lifetime reproductive success (LRS) defined as the total number of zygotic offspring produced per zygote. However, in those species whose ecology is otherwise well-suited to individual-level population studies, the prenatal part of an individual's life is often difficult to observe. While uncertainty has long surrounded the fertilization status of unhatched bird eggs-hatching failure can arise through fertilization failure or prenatal mortality-2 recent studies show fertilization failure to be extremely rare within 2 of the most popular avian study species. As such, unhatched eggs are highly reliable indicators of prenatal mortality. Although the generality of these results remains unclear, they demonstrate that prenatality can be incorporated into the observable lifespan of free-living animals. This allows zygotic LRS to be retrospectively quantified using historical nest observations and facilitates a more complete characterization of the evolutionary dynamics of wild populations.