Evolution最新文献

Local adaptation is the biological process by which native populations become more fit. Intraspecific patterns of local adaptation occur through shifts in allele frequency within or near genes and may occur similarly across species. Identifying repeated adaptation across species increases statistical power to determine causal genes driving adaptation and reveals insights into the nature of evolution. These types of insights could have theoretical and applied applications, particularly as the climate continues to change. We interrogate repeated molecular adaptation across 13 eucalypt species. In total, we found 38 candidate genes with shared putatively adaptive signals in as many as 12 species. This suite of genes contains important functions, including MYB proteins, acyl-CoA dehydrogenases and Leucine-rich kinases. Species with restricted and widespread geographical distributions shared putative patterns of adaptation, and phylogenetic closeness did not increase patterns of repeated adaptation compared to geographic overlap. This work provides further evidence that repeated adaptation can occur among orthologs, which may play a consistent role in local adaptation.

Understanding organismal responses to environmental change is a central goal of biology with profound implications for the conservation of biodiversity. Widespread evidence of epigenetic modifications in response to environmental stress, including those inherited across generations, has led to considerable speculation about their role in organismal responses to environmental change. Yet, the magnitude and fitness consequences of epigenetic marks carried beyond maternal inheritance are largely unknown. Here, we tested how transgenerational epigenetic inheritance (TEI) shapes the phenotypic response of Daphnia clones to the environmental stressor Microcystis. We split individuals from each of eight genotypes into exposure and control treatments (P0 generation) and tracked the fitness of their descendants to the F3 generation. We found transgenerational epigenetic exposure to Microcystis led to reduced survival and growth rates and no consistent effect on offspring production. TEI was associated with increases in trait variance, suggesting the potential for heritable bet hedging driven by TEI. Taken together, our results demonstrate that TEI causes substantial-but not adaptive-trait shifts, suggesting transgenerational adaptive plasticity may be rare.

Natural selection acts on traits at different scales, often with opposing consequences. This article identifies the particular forces that act at each scale and how those forces combine to determine the overall evolutionary outcome. A series of extended models derive from the tragedy of the commons, illustrating opposing forces at different scales. Examples include the primary tension between conflict and cooperation and the evolution of virulence, sex ratios, dispersal, and evolvability. The unified analysis subsumes interactions within and between species by generalizing multitrait interactions. Expanded notions of recombination and cotransmission arise. The core theoretical approach isolates the fundamental forces of selection, including marginal valuation, correlation between interacting entities, and reproductive value. Those fundamental forces act as partial causes that combine at different temporal and spatial scales. Modeling focuses on statics, in the sense of how different forces at various scales tend to oppose each other, ultimately combining to shape traits. That type of static analysis emphasizes explanation rather than the calculation of dynamics. The article builds on the duality between explanation versus calculation in terms of statics versus dynamics. The literature often poses that duality as a controversy, whereas this article develops the pair as complementary tools that together provide deeper understanding. Along the way, the unified approach clarifies the subtle distinctions between kin selection, multilevel selection, and inclusive fitness, subsuming these topics into the broader perspectives of fundamental forces and multiple scales.

Adaptive radiation (AR), a process of rapid speciation and ecomorphological diversification, played an important role in generating past and contemporary global biodiversity. An unsolved question is what maintains high rates of speciation during AR, a phenomenon we call "speciation paradox". One possible explanation for resolving this paradox is a sequential trait evolution, i.e., a series of ecological diversifications, which enables evolving lineages to fully and more effectively exploit the ecological space. We tested this hypothesis using the highly diverse subterranean amphipod genus Niphargus. Niphargus shows distinct signatures of adaptive radiation both at the genus level and at the level of four larger clades. Our analysis revealed decoupled evolution of habitat-related traits and trophic-biology-related traits. Moreover, on a genus level, we found the evidence that AR commences with a tight association between speciation rates and the dynamics of habitat-related traits. At a later stage, speciation dynamics become associated with diversification of trophic-biology-related traits. This suggests that the dependence of macroevolutionary rates in this group switches among niche axes before saturation, resulting in prolonged high speciation rates during AR.

The evolutionary dynamics of color pattern diversification in animals is strongly influenced by visual interactions within and among species. While much attention has been given to color pattern variation in the human-visible range, perception outside this range is observed in a wide array of species and is poised to influence color pattern evolution. Butterfly species often show sensitivity to ultraviolet (UV) light, impacting wing color pattern diversification as their evolution is influenced by both predator vision and sexual selection. Here, we explore UV color pattern diversification in Papilionidae within a comparative phylogenetic framework, by quantifying variation from UV photographs of museum specimens using a machine-learning based method. We find decoupled dorsal and ventral UV color pattern evolution, with brighter and more rapidly evolving ventral sides, especially in males. Conversely, we find a smaller dorso-ventral difference in visible-light color patterns. Moreover, we find divergence in male ventral UV patterns in closely related sympatric species, even after accounting for variation due to visible-light pattern. These results suggest an influence of sexual selection on UV ventral pattern diversification. These findings highlight how the trade-off between sexual and natural selection may lead to contrasted evolution of ventral vs. dorsal sides of the same organ.

Sexual selection has been proposed to promote genetic variants that improve resistance to pathogens (a variant of the "good genes" hypothesis). Two key mechanisms linking sexual success and pathogen resistance have been proposed: the "condition-dependent" scenario, where general health improves both sexual traits and pathogen resistance, and the "context-dependent" scenario, where resistance to specific pathogens benefits sexual success only in certain environments. Few studies distinguish between these two mechanisms. Here, we used Drosophila melanogaster in an experiment designed to test for additive genetic relationship between males' sexual success and the resistance of its offspring to the fungal pathogen Metarhizium brunneum, and to investigate if this relationship depends on pathogen exposure during sexual selection as well as on offspring sex. In the absence of the pathogen, more sexually successful males sired less pathogen-resistant offspring whereas no relationship was detected when sires competed for paternity after pathogen exposure. For daughters, the relationship tended to be negative irrespective of sire's pathogen exposure. Thus, while we confirmed that sexual selection may act on genes affecting resistance in a context- and sex-dependent manner, we found no circumstances under which it promoted resistance, in contradiction to the "good genes" hypothesis.

Many species experience heterogeneous environments and adapt genetically to local condi- tions. The extent of such local adaptation depends on a balance between divergent selection and gene flow, but also on other factors such as phenotypic plasticity or the genetic architecture of traits. Here, we explore the role of life history in this process. We develop a quantita-tive genetics model and run individual-based simulations to contrast the evolution of local adaptation between short- and long-lived species. We show that local adaptation varies with a species' life cycle and how this cycle modulates the scheduling of selection and dispersal among stages. When a longer generation time is associated with more frequent events of selection than dispersal, local adaptation is more pronounced in long-lived than in short-lived species. Contrastingly, if dispersal occurs more frequently than selection, long-lived species evolve weaker local adaptation. Our simulations confirm these findings and further show how longevity shapes additive genetic variance, effective dispersal between patches, and the genetic response at quantitative trait loci. Taken together, our results suggest that the effect of longevity on local adaptation depends on the specifics of a species' life cycle, potentially explaining why current meta-analyses have not consistently detected this effect.

Sister lineage comparisons provide a valuable tool for understanding evolutionary origins of species-rich clades and the role of habitat transitions in lineage diversification. Percomorpha, comprising over 18,900 species, represents one of the most species-rich lineage of vertebrates. However, the phylogenetic resolution of its sister lineage remains unclear, obscuring whether contrasts in histories of diversification provide insights into the factors that gave rise to this clade's high diversity. Using 887 ultraconserved element loci and eight Sanger-sequenced nuclear genes, we resolve the phylogenetic relationships of the three closest relatives of Percomorpha-the roughies, flashlightfishes, porcupinefishes and fangtooths (Trachichthyiformes), the squirrelfishes and soldierfishes (Holocentridae), and the whalefishes, bigscales, and alfonsinos (Berycoidei)-and the placement of percomorphs among them. Contrary to expectations from the fossil record, we demonstrate that living lineages of Berycoidei, Holocentridae, and Trachichthyiformes all diversified after the Cretaceous-Paleogene mass extinction. Our findings show that multiple clades in Trachichthyiformes and Berycoidei independently colonized deep ocean habitats during the climatically unstable Eocene and Oligocene and shallow-water reefs during the extensive hotspot migration and faunal turnover of the Early Miocene. This coincided with the evolution of novel life history traits, including pelagic cnidarian-mimicking larvae and extreme sexual dimorphism in some deep-sea forms. Because of their recent invasions of these habitats, the closest relatives of Percomorpha are not ideal for understanding the origins of this exceptionally species-rich clade in the marine realm.

The evolution of aposematism, in which prey exhibit conspicuous signals indicating the presence of anti- predator defenses, is puzzling. Before predators learn to associate the signal with defense, increased visibility makes the conspicuous prey highly vulnerable to predation. Although several hypotheses have been proposed to explain the evolution of aposematism, they often assume that these signals can only be recognized by predators. Yet, many studies show that aposematic signals can also be involved in mate choice. Here, we demonstrate that some aposematic signals may have originally evolved as mating signals driven by sexual selection. In this study, we analyze a mathematical model to explore how sexual selection can drive the evolution of aposematism. We thereby identify key features of this 'sexual selection hypothesis' for the origin of aposematism to be tested with empirical data. Our results show that the evolution of conspicuous signals through sexual selection increases the visibility of prey to predators and thus predation pressure. This, in turn, promotes the evolution of defense mechanisms, ultimately leading to aposematism when predators learn to associate the signal with defense. Additionally, we show that when sexual selection drives the evolution of aposematism, it often results in sexual dimorphism in both signaling and defense traits.

We study how rugged fitness landscapes are explored by spatially structured popula- tions with demes on the nodes of a graph, connected by migrations. In the weak mutation and rare migration regime, we find that, in most landscapes, migration asymmetries as- sociated with some suppression of natural selection allow the population to reach higher fitness peaks first. In this sense, suppression of selection can make early adaptation more efficient. However, the time it takes to reach the first fitness peak is then increased. We also find that suppression of selection tends to enhance finite-size effects. Finite struc- tures can adapt more efficiently than very large ones, especially in high-dimensional fitness landscapes. We extend our study to frequent migrations, suggesting that our conclusions hold in this regime. We then investigate the impact of spatial structure with rare migra- tions on long-term evolution by studying the steady state of the population with weak mutation, and introducing an associated steady-state effective population size. We find that suppression of selection is associated to small steady-state effective population sizes, and thus to small average steady-state fitnesses.