Journal of Evolutionary Biology最新文献

Through behavioural adaptation, organisms can alter their environment, and consequently, their exposure to selective pressures. In contrast, physiological traits adapt by accommodating environmental influences. Here, we examine how the coevolution of behavioural and physiological traits is shaped by their different relationships to the environment by modelling the adaptation of species with temperature-dependent sex determination to climate change. In these species, pivotal temperature and maternal nesting behaviour can evolve in response to rising temperatures that destabilise sex ratios. We used individual-based simulation modelling to ascertain the relative response to selection of these traits and determine how temperature-dependent embryonic survival and behavioural plasticity influence their coevolution. We found that pivotal temperature evolved to ameliorate sex-ratio bias more readily than nesting behaviour, though behaviour played an important role in adaptation to extreme environments. Selection favoured increased behavioural evolution when embryonic survival depended on nest temperature, while plasticity reduced the adaptive potential of behaviour. We demonstrate that the capacity of behavioural traits to respond to multiple selective pressures has a substantial impact on the coevolution of behavioural and physiological traits. Our findings highlight the complex interactions that occur when species adapt to new environments and the potential for plasticity to shape the course of evolution.

Kin recognition in plants may lead to plastic changes in their behavior, such as altering their floral display size. In this study, we conducted evolutionary simulations of the two floral tactics utilized by plants depending on the genetic relatedness of their neighboring plants. We found that the evolutionary consequences of the floral display size in plants can be classified into four types, based on whether the floral display size increased or decreased in comparison with the case plants disable of kin recognition. As a typical result, the plants that grew with kin behaved altruistically by increasing their floral display size, whereas those that coexisted with strangers behaved selfishly by reducing their floral display size, as is observed in the field. The kin recognition and resultant evolution of the floral display size had the spillover effect on the population scale. Kin recognition generally increased the intraspecific variation in the floral display size and seed production, and decreased the genetic diversity of plant populations.

Sex chromosomes are theorised to stop recombining and become fixed, yet many taxa show ambiguous genomic signals of sex consistent with either continuous recombination or sex chromosome turnover. Elucidating the basis of sex chromosome conservation or alternatively, turnover, requires comparative studies among natural populations with shared evolutionary histories. The African Great Lake radiations of cichlid fishes display an outstanding propensity to rapidly evolve novel sex-linked regions, yet older cichlid lineages external to these radiations seem to show conservation of a few sex chromosomes. Here, we studied sex-determining regions of species uniquely representing two older lineages within Lake Tanganyika; Oreochromis tanganicae (Oreochromini) and Tylochromis polylepis (Tylochromini). Using a combined SNP- and kmer-based approach, we confirm a ZW system on linkage group (LG) 3 in O. tanganicae, but not the previously proposed sex-determining gene. However, in T. polylepis, no clear region of sex-association could be identified, although kmer-based analyses point towards LG12 as a candidate sex chromosome. Additionally, we investigated four other species from older, non-East African radiation lineages and confirm LG3 to be frequently associated with sex, but also find stronger signals of sex association on different chromosomes not previously discovered. Combined, these results suggest that homomorphic sex chromosomes are a feature of African cichlids at large. LG3 frequently harbours regions of sex-linkage, but is often polygenic with more strongly sex-linked regions on other chromosomes, possibly denoting its ancestral function as sex-determining across African cichlids, that leaves traces as novel sex-determining regions emerge. Our investigation captures this in a phylogenetic context, from emergence, to fixation, or turnover to a new sex chromosome.

Phenotype-environment associations in neonatal animals may arise in wild environments by virtue of ecological dynamics within the nest. Such dynamics may be of special importance to the evolution of temperature-dependent sex determination (TSD), an enigmatic trait which can be adaptive when the incubation temperatures that affect sexual differentiation also have differential effects on fitness of the sexes. To infer causal effects of the nest environment on fitness-relevant phenotypes, we apply structural equation modeling (SEM) to a 14-year dataset of 3085 individual embryos whose position in 179 wild snapping turtle nests could be estimated. We find that temperature has a positive effect on hatchling size, and that the same temperatures that predict hatchling size also predict sex of hatchlings. Further, the probability that embryos develop as males is correlated with hatchling size in the wild, where across all environments, males are slightly and significantly larger than females at hatching. Our SEM reveals that the covariance between size and sex arises because of temperature effects on size, and because of a predictable covariance between egg placement within the nest coupled with maternal effects on egg size. Finally, embryos deep in the nest have a high probability of becoming male even in the hottest years. Our study suggests ecological dynamics occurring within the nest are an interesting and underappreciated source of phenotypic variation. Our study also supports the view that TSD is an adaptive trait, rather than a neutral trait, by showing consistent associations between phenotype and temperature in wild nests of a TSD reptile.

Investigating the evolution of complex traits in nature requires accurate assessment of their genetic basis. Quantitative genetic (QG) modeling is frequently applied to estimate the additive genetic variance (VA) in traits, combining phenotypic and pedigree data from a sample of individuals. Whether reconstructed from social links or molecular markers, empirical pedigrees differ in completeness, genealogical error rates and other attributes that can impact QG estimation. Here we investigate this impact using human genealogical data for six French-Canadian (FC) populations originating from the same genetic founding source but differing in their pedigrees' attributes. First, we simulated phenotypic values along pedigrees and under different trait architecture and 'true' parameter values (e.g. VA). Then we fitted mixed effects 'animal' models to these simulated data, to assess how QG estimation was impacted by pedigree attributes. Our results show that pedigree size and depth were important determinants of the precision, but not accuracy, of genetic parameter estimates. In contrast, pedigree completeness and entropy, two attributes related to the density of genealogical links, were not clearly associated with the performance of parameter estimation. Noticeably, a slight increase in the genealogical error rate was sufficient to cause a detectable underestimation of VA. Including maternal genetic effects into the simulations lead to a slight underestimation of VA with pedigrees of smaller size and depth. Despite originating from the same genetic source, the six pedigrees yielded wide variations in QG estimates under identical conditions. These findings highlight the importance of sensitivity analyses in pedigree-based genetic studies on natural populations.

Researchers have shown growing interest in using deep neural networks (DNNs) to efficiently test the effects of perceptual processes on the evolution of colour patterns and morphologies. Whether this is a valid approach remains unclear, as it is unknown whether the relative detectability of ecologically relevant stimuli to DNNs actually matches that of biological neural networks. To test this, we compare image classification performance by humans and 6 DNNs (AlexNet, VGG-16, VGG-19, ResNet-18, SqueezeNet, and GoogLeNet) trained to detect artificial moths on tree trunks. Moths varied in their degree of crypsis, conferred by different sizes and spatial configurations of transparent wing elements. Like humans, four of six DNN architectures found moths with larger transparent elements harder to detect. However, humans and only one DNN architecture (GoogLeNet) found moths with transparent elements touching one side of the moth's outline harder to detect than moths with untouched outlines. When moths took up a smaller proportion of the image (i.e., were viewed from further away), the camouflaging effect of transparent elements touching the moth's outline was reduced for DNNs but enhanced for humans. Viewing distance can thus interact with camouflage type in opposing directions in humans and DNNs, which warrants a deeper investigation of viewing distance/size interactions with a broader range of stimuli. Overall, our results suggest that human and DNN responses had some similarities, but not enough to justify widespread use of DNNs for studies of camouflage.

Allometry, the relationship between body size and the size of other body parts, explains a significant portion of morphological variation across biological levels, at the individual level, within and between species. We used external morphology measurements of 6 Triturus (sub)species, focussing on the T. marmoratus species group, to explore allometric parameters within and between taxa. We tested for allometry of sexual size dimorphism in body, head, and limb dimensions and examined whether intraspecific allometry directed evolutionary allometry, as described by Rensch's rule. Our findings indicated that female-biased trunk and head dimensions exhibited positive allometry, whereas male-biased limb dimensions showed isometric relationships or weak correlations with body size. Morphological divergences between sexes occurred along common allometric slopes, most often through changes in the intercepts. Among taxon, comparisons revealed that (sub)species diverged in the direction of the allometric slopes. In line with Rensch's rule, sexual size dimorphism in female-biased traits significantly decreased as overall body size increased. However, the observed intraspecific allometric parameters deviated from theoretical expectations because the steepest allometric slopes for female-biased traits were recorded in the larger species. Our results contribute to understanding the dynamics of allometric relationships and sexual dimorphism in amphibians and provide a robust baseline for future comparative analyses.

Identifying the presence and strength of reproductive isolating barriers is necessary to understand how species form and then remain distinct in the face of ongoing gene flow. Here, we study reproductive isolation at two stages of the speciation process in the closely related mushroom-feeding species Drosophila recens and Drosophila subquinaria. We assess 3 isolating barriers that occur after mating, including the number of eggs laid, the proportion of eggs laid that hatched, and the number of adult offspring from a single mating. First, all 3 reproductive barriers are present between D. recens females and D. subquinaria males, which are at the late stages of speciation but still produce fertile daughters through which gene flow can occur. There is no evidence for geographic variation in any of these traits, concurrent with patterns of behavioural isolation. Second, all 3 of these reproductive barriers are strong between geographically distant conspecific populations of D. subquinaria, which are in the early stages of speciation and show genetic differentiation and asymmetric behavioural discrimination. The reduction in the number of eggs laid is asymmetric, consistent with patterns in behavioural isolation, and suggests the evolution of postmating prezygotic isolation due to cascade reinforcement against mating with D. recens. In summary, not only may postmating prezygotic reproductive barriers help maintain isolation between D. recens and D. subquinaria, but they may also drive the earliest stages of isolation within D. subquinaria.

Communication via evolved signals is ubiquitous (both within and between species) in the natural world. However, how honest we should expect signals to be remains an open question. Hybrid equilibria are a form of equilibria predicted by discrete signaling games in which signalers are sometimes dishonest and signals do not completely reliably convey information on signaler quality. While these equilibria have been theoretically demonstrated in several signaling games, their dynamics in a stochastic simulation of evolutionary trajectories (that include representation of the inherent noise expected in evolution in the natural world) have not previously been studied. In this paper, we present an agent-based simulation of a discrete signaling game which exhibits hybrid equilibria. We find that while hybrid equilibria are evolutionarily attractive where they exist, populations exhibit variable and often drastic oscillating behavior around the predicted equilibrium values. We discuss how these dynamics might offer valuable opportunity for detecting hybrid equilibria in natural populations.