Journal of Evolutionary Biology最新文献

Adaptive plasticity allows organisms to interact with heterogenous environments and respond to environmental change. Population-level comparisons of plasticity provide insights into the selective factors driving plasticity evolution and properties of reaction norms likely to evolve. We test how thermal environments shape melanin plasticity in response to a seasonal cue in the white-lined sphinx moth, Hyles lineata. We compare how photoperiod affects melanization in two populations that experience different thermal environments: Colorado and Arizona. If thermal environment drives differences in melanin plasticity in response to photoperiod, then the reaction norms should differ in intercept (higher melanization in Colorado larvae across photoperiods, due to colder temperatures), slope (steeper in Arizona larvae, due to a larger range of temperatures across relevant photoperiods), and shape (linear in Arizona larvae and quadratic in Colorado larvae, due to the relationship between photoperiod and temperature). Results are partially consistent with these predictions: the Arizona population had a steeper slope, but a higher intercept. The Colorado population likely relies more heavily on temperature cues to inform melanization, requiring lower temperatures to increase melanin. Populations did not differ in reaction norm shape, suggesting that while slope and intercept are labile, there may be constraints on the evolution of shape. Because only two populations were compared in this study, replication at the population level is needed to corroborate the generality of these results. This study highlights the complexity of plasticity evolution and the need to consider multiple cues and selective pressures, as well as potential constraints on the evolution reaction norms.

Evolution in variable environments is predicted to disfavour genetic canalization and instead select for alternative strategies, such as phenotypic plasticity or possibly bet-hedging, depending on the accuracy of environmental cues and type of variation. While these two alternatives are often contrasted in theoretical studies, their evolution are seldom studied together in empirical work. We used experimental evolution for 30 generations in the nematode worm Caenorhabditis remanei to simultaneously study the evolution of plasticity and bet-hedging in environments differing only in their temperature variability, where one regime is exposed to faster temperature cycles between 20 and 25 °C, with little autocorrelation between parent and offspring environment, while the other regime had slowly increasing temperature with high autocorrelation in temperature between parent and offspring. These two environments had the same average temperature over evolutionary time, but one varied with larger magnitude on a shorter time scale. After experimental evolution, we scored adult size and fitness in full siblings reared in two different temperatures, optimal 20 °C and mildly stressful 25 °C. Experimental evolution in fast temperature cycles resulted in the evolution of increased body size plasticity but not increased bet-hedging, compared to evolution in the slowly changing environment. Plasticity followed the temperature-size rule as size decreased with increasing temperature and this plastic response was adaptive. In addition, we documented substantial standing genetic variation in body size, which represents a potential for further evolutionary change.

New genes can emerge de novo from non-genic genomic regions. In budding yeast, computational predictions have shown that intergenic regions harbour a higher-than-expected propensity to encode transmembrane domains, if theoretically translated into proteins. This propensity seems to be linked to the high prevalence of predicted transmembrane domains in evolutionarily young genes. However, what accounts for this enriched propensity is not known. Here, we show that specific arrangements of polyA/T tracts, which are abundant and enriched in yeast intergenic regions, explain this observation. These tracts are known to function as nucleosome-depleted regions, which prevent or reduce nucleosome formation to enable transcription of surrounding genes. We provide evidence that these polyA/T tracts have been repeatedly coopted through de novo gene emergence for the evolution of novel small genes encoding proteins with predicted transmembrane domains. These findings support a previously proposed "transmembrane-first" model of de novo gene birth and help explain why evolutionarily young yeast genes are rich in transmembrane domains. They contribute to our understanding of the process of de novo gene evolution and show how seemingly distinct but potentially interacting levels of functionality can exist within the same genomic loci.

This study explores the thermal tolerance of geographically isolated Mediterranean fruit fly, Ceratitis capitata (Wiedemann) populations and examines how response to thermal stress is associated with its capacity to invade cooler temperate regions. The remarkable invasion success of C. capitata, facilitated by global fruit trade and human activity, offers an opportunity to explore the role of phenotypic plasticity in shaping invasion dynamics. We assessed critical thermal limits across populations from varying latitudes, examining the effects of latitude, climate, and thermal acclimation. Critical thermal minimum (CTmin) was lower in populations obtained from colder, higher-latitude regions and influenced by climatic variability. While acclimation temperature had a marginally non-significant effect on CTmin, its interaction with latitude was significant, showing a pronounced increase in CTmin with acclimation at higher latitudes. Critical thermal maximum (CTmax) was influenced by microclimatic variability, with higher values in populations originating from colder, higher-latitude sites. Acclimation temperature increased CTmax across populations, with females exhibiting higher CTmax values than males. Significant interactions between latitude and climatic variability (PC1) for both CTmin and CTmax underscore the role of local climate conditions in shaping thermal tolerance. These findings enhance our understanding of the physiological mechanisms driving the invasive potential of C. capitata and its adaptation to temperate climates.

Unmated females in haplodiploid populations may enjoy reproductive success but with the constraint that all their offspring-developing from unfertilised eggs-are male. The presence of such females, constrained to produce only male offspring, is expected to lead to a corresponding female bias being favoured among the offspring of unconstrained females. Godfray (J Evol Biol 3, 3-17) derived a mathematical expression for the unbeatable sex allocation strategy for unconstrained females in the context of local mate competition in 2-foundress patches, and concluded that there is negligible impact of the presence of constrained females on the unbeatable sex allocation of unconstrained females. However, Godfray's result assumes diploid-rather than haplodiploid-genetics and his derivation contains a mathematical error. We correct Godfray's error and extend his model to incorporate haplodiploid genetics. This results in a more substantial impact of constrained females on the sex allocation behaviour of unconstrained females under local mate competition.

Predator and prey communities are important putative drivers of phenotypic variation in consumers. However, in natural food webs, we often lack an understanding of the ecological interactions by which the species community affects consumer traits. In a comparative study, we explore how phenotypic variation of 34 Greenlandic threespine stickleback populations is affected by the presence and absence of an intraguild predator (Arctic char). In the presence of char, we find that stickleback have a larger body size but a similar head size, resulting in allometric changes (i.e., change in relative head size) that are consistent with resource mediation of ontogenetic growth trajectories observed in other fishes. Using path analysis, we show that the observed shift in the relative head size of stickleback can be partly explained by predator-mediated effects on the species composition and biomass of zooplankton. Our study suggests that top predators can indirectly affect resource limitation of consumers via changes in the prey communities of consumers, and thereby influence the allometry of consumer traits, likely via allocation tradeoffs. These results have important implications for interpreting the putative causes of allometric variation among populations and for using comparative studies to discern the ecological causes of phenotypic variation in natural populations.

Despite numerous lineages exhibiting ecologically and phenotypically similar species across continents, the interplay between evolutionary convergence and biogeographical dispersal in shaping continental community assembly remains largely unknown. Tropical wandering spiders (Ctenidae) are a diverse group of terrestrial predators with a pantropical distribution, exhibiting a variety of specialised morphotypes across different habitats. We used phylogenetic comparative methods to investigate the role of ecomorphological convergence through continental in situ diversification and biogeographic dispersal in assembling tropical wandering spiders (Ctenidae). We address three evolutionary questions: (1) Did independent habitat shifts result in the repeated origin of similar morphologies? (2) Is similarity in morphology across continental assemblages caused by evolutionary convergence or by biogeographic dispersal? (3) Are there differences in dispersal rates between different ecomorphs (ground and arboreal) and if so how does this affect community assembly? Ancestral habitat reconstruction suggests that ctenids were likely originally arboreal and later colonized terrestrial habitats at least six times independently. We detected morphological shifts on the phylogeny in carapace height, spine length of the first legs, and leg span that were associated with habitat transitions. Our biogeographic analyses suggest that ground-dwelling ctenids show significantly higher dispersal rates compared to arboreal ctenids. Our findings imply that ctenid ecomorphological diversity in certain continental areas originated from in situ diversification within specific biogeographical regions, driven by multiple habitat shifts closely linked to morphological changes. Furthermore, our study reveals that ctenid assembly across various regions has also been influenced by long-distance dispersal events of evolutionarily conserved ground-adapted forms.

The tendency for the genital morphology of animals to diverge more rapidly than other traits is one of the most pervasive evolutionary patterns in animal form. Current controversy regarding explanations of this pattern stems in part from the difficulty of observing the behaviour of male genitalia during copulation. This limitation is reduced in tipuloid crane flies, because most of the male's elaborate, divergent genital structures remain outside the female during copulation. Observations of genital behaviour during copulation in 45 species in 21 genera and subgenera, the most extensive sample of genital behaviour in any comparable group of animals, show a combination of trends that fits better with the stimulation version of the cryptic female choice hypothesis than with any of the other hypotheses commonly cited to explain rapid divergent genital evolution: sustained, rhythmic male genital movements such as brushing and tapping; frequent female facilitation of stimulation; lack of consistent morphological coevolution between corresponding male and female structures; lack of forceful male manipulations of females; lack of female "defenses" that impede male stimulation; and lack of direct male interference with other males' sperm. Tipuloids are atypical among Diptera in generally lacking rhythmic, forceful genital thrusting and squeezing.

Whether evolution is predictable has been tested in evolutionary biology by comparing lineages that experienced parallel evolution. For example, the repeatability of gene expression between strains was examined in the experimental evolution of bacteria. However, whether it is possible to predict the evolutionary fate of a gene (i.e., loss or retention) after an organism colonizes a new habitat and experiences a long period is not sufficiently clear. Here, we investigate a visual gene set in two species of eyeless trechine beetles (Coleoptera: Carabidae: Trechinae), which are thought to have colonized caves independently, and show that many of the lost genes and retained genes are common between them. We also estimate the pleiotropy that represents the extent to which these genes act in several tissues, using gene expression data in a model organism, and show that commonly lost genes have low pleiotropy. Our results suggest that the loss and retention of a visual gene set are relatively easy to predict in cave-dwelling trechine beetles. Furthermore, this study supports the possibility that even evolutionary fates of genes, which occur after a long period, are influenced by the functional constraints of these genes.