Journal of Evolutionary Biology最新文献

Dispersal is a key demographic parameter that plays an important role in determining spatial population dynamic and genetic structure. Linking differences in dispersal patterns to key life-history traits is often confounded by inconsistent environmental pressures experienced by different populations. To explore the link between dispersal and life history, we focus on a site where oviparous and viviparous lineages of the common lizard (Zootoca vivipara) are found adjacent to each other. We take advantage of this shared environment to investigate parity-specific dispersal patterns using high resolution, individual-level spatial genetic autocorrelation and population genomic approaches (11,726 SNPs; 293 oviparous and 310 viviparous individuals). We found isolation-by-distance patterns to be present in both the oviparous and viviparous populations. Density was 2.5 times higher in the viviparous population than the oviparous one, though heterozygosity and genetic diversity measures were similar in the two populations. We found marked differences in the extent of genetic neighbourhoods between the lineages, with the viviparous population showing both dispersal (σ) and spatial genetic autocorrelation (Moran's I) at two-fold greater geographic distances than the oviparous population. We found clear evidence of male-biased dispersal from genetic estimates in the viviparous population. In the oviparous population, evidence of male-biased dispersal is weak or absent. These differences are likely to be closely linked to specific requirements of the alternative reproductive strategies and may be the demographic consequences of mother-offspring interactions. Fine-scale geographic and individual-level measures are key to understanding parity mode differences at microevolutionary scales and to better identifying their ecological and evolutionary impacts.

The dynamics of mating interactions can vary in response to a wide variety of environmental factors. Here, we investigate the potential for individuals to vary consistently in the environmental conditions under which they actively engage in courtship. Specifically, we quantify variation in how courtship activity changes with environmental temperature across levels of biological organization in Enchenopa binotata treehoppers. Male E. binotata produce vibrational courtship signals and receptive females respond with their own sex-specific vibrational courtship signal. We tested each individual twice for the production of courtship signals across a range of ecologically-relevant temperatures (18 - 36 °C). Then, we measured repeatability and variability in the resulting thermal courtship activity curves, including the temperature of peak activity and tolerance to thermal extremes. We also looked at patterns of variation across populations and sexes. We found minimal variation across populations, but significant variation across individuals. Specifically, we found prevalent repeatability in how thermally generalized or specialized individuals are. However, repeatability was limited to females only. We also found higher variability in female traits than in male traits, although patterns of variability did not always predict patterns of repeatability. These results suggest that thermal variation could alter the dynamics of mate competition, and that-due to potentially different selective optima for males and females-the sexes may respond to changes in temperature in different ways. Specifically, females show a higher potential to adapt but males show a higher potential to be more robust to changes in temperature due to overall higher courtship activity across temperatures.

Trade-offs are a fundamental concept in evolutionary biology because they are thought to explain much of nature's biological diversity, from variation in life-histories to differences in metabolism. Despite the predicted importance of trade-offs, they are notoriously difficult to detect. Here we contribute to the existing rich theoretical literature on trade-offs by examining how the shape of the distribution of resources or metabolites acquired in an allocation pathway influences the strength of trade-offs between traits. We further explore how variation in resource distribution interacts with two aspects of pathway complexity (i.e., the number of branches and hierarchical structure) affects tradeoffs. We simulate variation in the shape of the distribution of a resource by sampling 106 individuals from a beta distribution with varying parameters to alter the resource shape. In a simple "Y-model" allocation of resources to two traits, any variation in a resource leads to slopes less than -1, with left skewed and symmetrical distributions leading to negative relationships between traits, and highly right skewed distributions associated with positive relationships between traits. Adding more branches further weakens negative and positive relationships between traits, and the hierarchical structure of pathways typically weakens relationships between traits, although in some contexts hierarchical complexity can strengthen positive relationships between traits. Our results further illuminate how variation in the acquisition and allocation of resources, and particularly the shape of a resource distribution and how it interacts with pathway complexity, makes its challenging to detect trade-offs. We offer several practical suggestions on how to detect trade-offs given these challenges.

The central dogma of molecular biology can be conceptualised as the division of labour between templates and catalysts, where templates transmit genetic information, catalysts accelerate chemical reactions, and the information flows from templates to catalysts but not from catalysts to templates. How can template-catalyst division evolve in primordial replicating systems? A previous study has shown that even if the template-catalyst division does not provide an immediate fitness benefit, it can evolve through symmetry breaking between replicating molecules when the molecules are compartmentalised into protocells. However, cellular compartmentalisation may have been absent in primordial replicating systems. Here, we investigate whether cellular compartmentalisation is necessary for the evolution of the template-catalyst division via symmetry breaking using an individual-based model of replicators in a two-dimensional space. Our results show that replicators evolve the template-catalyst division via symmetry breaking when their diffusion constant is sufficiently high, a condition that results in low genetic relatedness between replicators. The evolution of the template-catalyst division reduces the risk of invasion by "cheaters," replicators that have no catalytic activities, encode no catalysts, but replicate to the detriment of local population growth. Our results suggest that the evolution of the template-catalyst division via symmetry breaking does not require cellular compartmentalization and is, instead, a general phenomenon in replicators with structured populations.

The evolutionary forces arising from differential dispersal are known as "spatial sorting," distinguishing them from natural selection arising from differential survival or differential reproductive success. Spatial sorting is often considered to be transient because it is offset by the return of dispersers in many cases. However, in riverine systems, spatial sorting by downstream dispersal can be cumulative in habitats upstream of migration barriers such as weirs or falls, which can block the return of the dispersers. Terraced rice paddies are often found on steep mountain slopes in Japan and often incorporate small streams with numerous migration barriers. This study investigated the morphological features of fat minnow, Rhynchocypris oxycephalus jouyi (Cyprinidae), inhabiting above-barrier habitats of the small streams flowing through flood-prone terraced rice paddies and examined their function via a mark-recapture experiment. Although this study did not reveal a consistent pattern across all local populations, some above-barrier populations were characterized by individuals with a thinner caudal peduncle, thinner body, and longer ventral caudal fin lobes than those in neighbouring mainstream populations. A mark-recapture experiment during minor flooding showed that a thinner caudal peduncle and deeper body helped fat minnow avoid downstream dispersal and ascend a small step, and suggested that a longer ventral caudal fin lobe was important for ascending. These results suggest that the caudal morphologies of some above-barrier populations avoid or reduce the risk of downstream dispersal, supporting the idea that spatial sorting shapes functional traits, enhancing the spatial persistence of individuals in upstream habitats.

In evolutionary game theory, a relative comparison of the cost and benefit associated with obtaining a resource, called payoff, is used as an indicator of fitness of an organism. Payoffs of different strategies, quantitatively represented as payoff matrices, are used to understand complex inter-species and intra-species interactions like cooperation, mutualism, and altruism. Payoff matrices, however, are usually treated as invariant with time - largely due to the absence of any empirical data quantifying their evolution. In this paper, we present empirical evidence of three types of resource-dependent changes in the payoff matrices of evolving Saccharomyces cerevisiae populations. We show that depending on the carbon source and participating genotypes, N-player games could collapse, be born, or be maintained. Our results highlight the need to consider the dynamic nature of payoff matrices while making even short-term predictions about population interactions and dynamics.

Larger effective populations (Ne) are characterized by higher genetic diversity, which is expected to predict population performance (average individual performance that influences fitness). Empirical studies of the relationship between neutral diversity and performance mostly represent species with small Ne, while there is limited data from the species-rich and ecologically important arthropods that are assumed to have large Ne but are threatened by massive declines. We performed a systematic literature search and used meta-analytical models to test the prediction of a positive association between neutral genetic diversity and performance in wild arthropods. From 14 relevant studies of 286 populations, we detected a weak (r = 0.15) but nonsignificant positive association both in the full data set (121 effect sizes) and a reduced data set accounting for dependency (14 effect sizes). Theory predicts that traits closely associated with fitness show a relatively stronger correlation with neutral diversity; this relationship was upheld for longevity and marginally for reproduction. Our analyses point to major knowledge gaps in our understanding of relationships between neutral diversity and performance. Future studies using genome-wide data sets across populations could guide more powerful designs to evaluate relationships between adaptive, deleterious and neutral diversity and performance.

Glacial periods have been considered as inhospitable environments that consist of treeless vegetation at higher latitudes. The fossil record suggests many species survived the Last Glacial Maximum within refugia, usually at lower latitudes. However, phylogeographic studies have given support to the existence of previously unknown high-latitude refugia that were not detected in the fossil record. Here, we test the hypothesis that cold-tolerant trees of Patagonia survived cold periods in microclimatically favourable locales where hybridization occurred between sister taxa. To study local presence through glacial periods in multiple refugia, we used pollen records and genetic information (isozymes, microsatellites, and combined nuclear and chloroplast DNA sequences) of population pairs of Nothofagus antarctica and N. pumilio that belong to the ancient subgenus Nothofagus which can potentially hybridize in nature, along their entire latitudinal range in Patagonia. Studied species share the N. dombeyi type pollen, which was abundant at >20% in the northernmost latitudinal bands (35-43°S), even during the Last Glacial Maximum. Mid- and southern latitudinal records (44-55°S) yielded lower abundances of ~10% that increased after c. 15.0 cal. ka BP. Therefore, fossil pollen evidence suggests a long-lasting local presence of Nothofagus throughout glacial-interglacial cycles but mostly as small populations between 44°S and 51°S. We found species-specific and shared genetic variants, the latter of which attained relatively high frequencies, thus providing evidence of ancestral polymorphisms. Populations of each species were similarly diverse, suggesting survival throughout the latitudinal range. Estimates of coalescent divergence times were broadly synchronous across latitudes, suggesting that regional climates similarly affected populations and species that hybridized through climate cycles, fostering local persistence.