Evolution最新文献

Sex determination was once thought to be unstable in ectothermic vertebrates, but several highly diversified groups of non-avian reptiles, such as iguanas sensu lato (Pleurodonta), appear to have conserved sex chromosomes. However, this statement has been criticized as being based on a parsimonious conclusion from limited sampling. Here, we tested sex chromosome homology in a further 35 species of pleurodont lizards, mainly of the family Anolidae. We demonstrated sex chromosome homology based on the comparison of the gene dosage of X-specific genes by quantitative PCR. Including these new data, the homology of sex chromosomes has so far been supported in 92 out of over 1,200 recently recognized species of Pleurodonta, representing all but one family of this clade. These very conserved sex chromosomes are at least as old as the basal split of Pleurodonta (estimated over 90 MY). In the case of the family Corytophanidae, all genera share different XX/XY sex chromosomes, which are thus over 25 million years old. We discuss the efficiency and limitations of the approach used for tests of the homology of sex chromosomes, as well as the reasons for the evolutionary stability of sex chromosomes in some lineages. We argue that to obtain a complete picture, all extant species should be tested for homology; however, until we reach this ambitious goal, parsimonious estimates in lineages where fragmentary data suggest stability of sex chromosomes, as in Pleurodonta, are substantiated.

Some trilobites underwent drastic morphological transformations through their development. The Ordovician trilobite Lonchodomas chaziensis transformed, in a single molt, from a globular protaspid larva to a drastically different adult-like meraspid juvenile. This metamorphosis may be related to a complete shift in lifestyle from a free-floating planktic life-mode into a bottom-dwelling benthic life-mode. By focusing on variation between individuals at distinct ontogenetic stages, shifts in covariation patterns through development can be identified to better understand this transformation. Organisms are composed of parts conceptualized in terms of modules i.e., semi-autonomous packages of highly correlated traits. Modularity is theorized to increase through ontogeny especially in arthropods which undergo metamorphosis. To test this hypothesis, we examine covariation patterns coincident with the restructuring of the trilobite head. Analyses show a decrease in the structure of modularity during metamorphosis and major shifts in the degree of modularity/integration during and preceding transformation. Further, the part which undergoes the most shape change becomes more integrated with other parts. As shape variation is organized in a mosaic fashion through ontogeny, modularity may have played a role in coordinated ontogenetic change among parts leading up to shifts in form and lifestyle occurring during the 'Plankton Revolution' of the early Paleozoic.

Sexual selection potentially drives the evolution of exaggerated traits used in intrasexual contests. However, the extent to which mating systems influence weapon morphology remains unclear. In fiddler crab males, an exaggerated claw functions both as a weapon and a signaling tool, varying according to the species' mating system. We examined claw evolution in male fiddler crabs, differentiating between two main mating strategies: (1) males defend their mating burrows (= "burrow"); (2) males do not mate in their own burrows (= "surface"). We measured claw morphological traits and tested whether the mating system affects their evolutionary rates, expecting "burrow" species to exhibit higher evolutionary rates. In general, claw size scales isometrically with body size across species. Both systems showed no correlation between claw elements and mechanical advantage, indicating the necessity of maintaining a conspicuous signaling tool alongside an efficient lever system for grip strength as body size increases. Contrary to predictions, however, "burrow" males exhibited lower evolutionary rates in claw traits than "surface" males, suggesting stronger stabilizing selection. These findings highlight the nuanced effects of sexual selection on male fiddler crab weapon evolution, suggesting that mating systems can modulate evolutionary trajectories, yet functional demands for dual weapon-signal roles constrain claw morphology.

Coevolutionary cycling in allele frequencies due to negative frequency-dependent selection-sometimes referred to as Red Queen Dynamics-is a key potential outcome of host-parasite coevolution. While many theoretical studies have focused on understanding the consequences of coevolutionary cycling for the evolution of sex and recombination, little is known about the impact of coevolutionary cycling on the evolution of other life history traits. It is therefore currently unknown how coevolutionary cycling in allele frequencies affects the evolution of key disease characteristics, such as virulence. Here, we combine population genetic and quantitative genetic approaches to theoretically determine the impacts of coevolutionary cycling in allele frequencies on the evolution of virulence in a free-living parasite. By varying the level of genetic specificity required for infection while controlling for the average infection rate, we induce coevolutionary cycles and examine their effects on virulence evolution. We show that coevolutionary cycling does indeed have a strong impact on virulence evolution, with more specific infection genetics and higher allelic diversity generally driving larger and more rapid cycles in allele frequencies, leading to selection for higher virulence. Our research provides new fundamental insights into the relationship between coevolutionary cycling and the evolution of virulence.

Historically, phylogenetic datasets had relatively few loci but were over-represented for cytoplasmic sequences (mitochondria and chloroplast) because of their ease of amplification and large numbers of informative sites. Under those circumstances, it made sense to contrast individual gene tree topologies obtained from cytoplasmic loci and nuclear loci, with the goal of detecting differences between them-so-called cytonuclear discordance. In the current age of phylogenomics and ubiquitous gene tree discordance among thousands of loci, it is important to distinguish between simply observing discordance between cytoplasmic trees and a species tree inferred from many nuclear loci and identifying the cause of discordance. Here, we examine what inferences one can make from trees representing different genomic compartments. While topological discordance can be caused by multiple factors, the end goal of many studies is to determine whether the compartments have different evolutionary histories: what we refer to as "cytonuclear dissonance." Answering this question is more complex than simply asking whether there is discordance, requiring additional analyses to determine whether genetic exchange has affected only (or mostly) one compartment. Furthermore, even when these histories differ, expectations about why they differ are not always clear. We conclude by pointing to current research and future opportunities that may help to shed light on topological variation across the multiple genomes contained within a single eukaryotic cell.

Omnivory has been hypothesized to be a macroevolutionary sink. A new study by Ochoa-Sanz et al. (2025) tests this hypothesis in Phyllostomidae, a highly ecologically and species-diverse bat family comprising species with different feeding habits, including omnivores and plant specialists. Plant specialists have higher speciation rates than omnivorous bat species, while balanced omnivores have higher speciation rates than plant-predominant ones. Part of the explanation for these differences might be related to the evolution of omnivory during periods of resource scarcity.

The regime of selection acting on a trait is expected to shape its static allometry. Few studies, however, have quantified the form of sexual selection acting on a trait in the wild to test whether the trait allometrically scales as predicted. Even fewer studies have tested these predictions using males expressing weapon polymorphism as part of their alternative mating strategies. Here, I use field data to test how sexual selection shapes scaling allometries of male weaponry in the Wellington tree wētā (H. crassidens), a male-trimorphic and harem-polygynous insect endemic to New Zealand. Contrary to the prediction that 10th instar males' large weaponry would scale hyperallometrically because it is under direct sexual selection, I found that 10th instar weaponry is not subject to direct sexual selection and scales hypoallometrically. Similarly, neither 8th nor 9th instar male weaponry experiences direct sexual selection, and their weaponry scales hyperallometrically and hypoallometrically, respectively. My study suggests that disentangling competing hypotheses for the evolution of scaling patterns of sexually selected traits must go beyond a simple viability-sexual selection dichotomy by also considering weapon function and the ecological context within which the weapon is used.

Winter is a formidable challenge for ectotherms that inhabit temperate climates. The extent to which winter conditions drive rapid adaptation, and separately, how selection from novel stressors affects adaptation to winter, remain poorly understood. Here, we use replicate populations of Drosophila melanogaster in a field experiment to test (i) whether winter conditions drive rapid adaptation and (ii) for trade-offs between insecticide resistance and overwintering survival. Following a longitudinal field experiment investigating the evolution of insecticide resistance, we tracked subsequent evolution during an overwintering period. In unexposed control populations, we detected parallel evolutionary shifts indicative of adaptation to winter conditions in multiple traits, including body size and fecundity. Additionally, populations that had evolved insecticide resistance during the growing season were more likely to go extinct than control populations. Further, both control and resistant populations showed patterns of lower resistance following the winter period, suggestive of a trade-off between overwintering success and insecticide resistance. Rapid evolutionary responses to winter conditions, and potential costs of resistance, provide important context for understanding overwintering performance in temperate insects with implications for pest management and ecosystem services.

Using the voice to produce sound is a widespread form of communication and plays an important role across diverse species and contexts. Variation in the rate and mode of sound production has been extensively studied within orders or classes, but understanding vocal signal evolution ultimately requires comparison across all major lineages involved. Here, we used phylogenetic comparative methods to investigate the evolution of dominant frequency and its association with body mass across a set of 873 species of mammals, birds, and frogs. Our results show that all vocal systems share the same general feature of the negative allometric relationship between body mass and dominant frequency, but that mammals clearly deviate compared to frogs and birds. We found mammals to vocalize at much higher frequencies and their signals evolved four- to sixfold faster compared to other tetrapod clades. Although all three groups strongly rely on vocal communication, our findings show that only mammals have extensively explored the spectral acoustic space. We argue that such high vocal diversity of mammals is made possible by their unique hearing system, and discuss the functional drivers that allowed their shared ancestors to evolve a richer array of frequencies than other tetrapods.

Ecological specialization is a result of the interplay between ecological and evolutionary processes. One iconic ecological specialization of the Neotropics involves birds that follow army ant swarms in feeding groups. Prior work has focused on a single avian family, the Neotropical antbirds (Thamnophilidae), but over a century of fieldwork has now revealed that ant-following occurs in hundreds of distantly related birds. To understand the relative contributions of shared ancestry and ecological specialization in the evolution of ant-following, we compiled a database of all Neotropical ant-following birds (n = 472 species) and their degree of specialization on army ants, and tested if (1) ant-following becomes increasingly specialized through evolutionary time and (2) ecomorphological functional traits predict ant-following behavior. Ancestral state reconstruction revealed that specialized ant-following evolved independently in 8 clades and 4 families of Neotropical birds (Antbirds: Thamnophilidae, Ovenbirds: Furnariidae, Tanagers: Thraupidae, and Cuckoos: Cuculidae). Ant-following behavior was highly conserved phylogenetically (Pagel's λ = 0.97), and specialized clades evolved from less specialized ancestors, with few evolutionary reversals. In contrast, ecomorphological traits poorly predicted the level of ant-following specialization across species. Our results suggest increasing specialization on army ants is governed by niche conservatism, not ecological specialization.