Evolution Of Phenotypic Traits Research Articles

Ancient hybridization leads to the repeated evolution of red flowers across a monkeyflower radiation.

The reuse of old genetic variation can promote rapid diversification in evolutionary radiations, but in most cases, the historical events underlying this divergence are not known. For example, ancient hybridization can generate new combinations of alleles that sort into descendant lineages, potentially providing the raw material to initiate divergence. In the Mimulus aurantiacus species complex, there is evidence for widespread gene flow among members of this radiation. In addition, allelic variation in the MaMyb2 gene is responsible for differences in flower color between the closely related ecotypes of subspecies puniceus, contributing to reproductive isolation by pollinators. Previous work suggested that MaMyb2 was introgressed into the red-flowered ecotype of puniceus. However, additional taxa within the radiation have independently evolved red flowers from their yellow-flowered ancestors, raising the possibility that this introgression had a more ancient origin. In this study, we used repeated tests of admixture from whole-genome sequence data across this diverse radiation to demonstrate that there has been both ancient and recurrent hybridization in this group. However, most of the signal of this ancient introgression has been removed due to selection, suggesting that widespread barriers to gene flow are in place between taxa. Yet, a roughly 30 kb region that contains the MaMyb2 gene is currently shared only among the red-flowered taxa. Patterns of admixture, sequence divergence, and extended haplotype homozygosity across this region confirm a history of ancient hybridization, where functional variants have been preserved due to positive selection in red-flowered taxa but lost in their yellow-flowered counterparts. The results of this study reveal that selection against gene flow can reduce genomic signatures of ancient hybridization, but that historical introgression can provide essential genetic variation that facilitates the repeated evolution of phenotypic traits between lineages.

The Evolution of Diet and Morphology in Insular Lizards: Insights from a Replicated Island Introduction Experiment.

Resource-limited environments may drive the rapid evolution of phenotypic traits and ecological preferences optimizing the exploitation of resources. Very small islands are often characterized by reduced food availability, seasonal fluctuations in resources and strong unpredictability. These features may drive the evolution of phenotypic traits such as high bite forces, allowing animals to exploit a wider variety of the available resources. They may also lead to more generalist dietary patterns in response to food scarcity. However, the lack of predators and competitors on such small islands often also leads to high densities and the evolution of strong sexual dimorphism, which may also drive the evolution of bite force. Here, we take advantage of a unique replicated introduction experiment to test whether lizards introduced into very small islands alter their feeding ecology and use different resources, resulting in the evolution of a large body size, large head size and large bite forces. Our results show that three years after their introduction, the island lizards were larger and had greater bite forces and more pronounced sexual dimorphism. However, the diets were only marginally different between animals from the source population on a very large nearby island and those on the islets. Moreover, distinct differences in diet between animals on the different islets were observed, suggesting that the local environment is a strong driver of resource use. Overall, lizards with absolutely and relatively (adjusted for body size) large bite forces did eat larger and harder prey. Taken together, our data suggest that intraspecific competition is an important driver of the rapid evolution of bite force, which may allow these lizards to exploit the scarce and fluctuating resources on the islets. Whether or not lizards will evolve to include other types of food such as plants in their diet, facilitated by their large bite forces, remains to be explored in future studies.

Phenotypic trait variations in the frog Nanorana parkeri: differing adaptive strategies to altitude between sexes

In many animals, changes in altitude drive adaptive variation in body size. However, how other phenotypic traits change when faced with different environments has been little studied in ectotherms. In this study, we selected the high Himalaya frog Nanorana parkeri as a model species for investigating the adaptive evolution of phenotypic traits that respond to altitude in both sexes. First, we found that body mass in populations at higher altitudes was lower than at lower altitudes in females, with no difference observed in males. Second, we found significant differences in fresh liver mass, fresh heart mass, and the ratio of liver mass to body mass with increasing altitude, while hindlimb length decreased with altitude in both sexes. Third, snout-urostyle length, hindlimb length, fresh heart mass and the ratio of heart mass to body mass showed significant negative correlations with increasing altitude in both sexes. In contrast, body mass showed a significant correlation with altitude in females but not males. On the other hand, the ratio of liver mass to body mass showed a significant correlation with altitude in males but not in females. Thus, the species displayed sex-specific organ-size variation along elevation gradients, which may trade-off in life history strategies among populations. We speculate that selection favours a larger heart and liver mass to maintain a higher respiratory rate and energy consumption as an adaptation to high-altitude environments.

Phenotypic divergence of traits that mediate antagonistic and mutualistic interactions between island and continental populations of the tropical plant, Tribulus cistoides (Zygophyllaceae).

Island systems have long served as a model for evolutionary processes due to their unique species interactions. Many studies of the evolution of species interactions on islands have focused on endemic taxa. Fewer studies have focused on how antagonistic and mutualistic interactions shape the phenotypic divergence of widespread nonendemic species living on islands. We used the widespread plant Tribulus cistoides (Zygophyllaceae) to study phenotypic divergence in traits that mediate antagonistic interactions with vertebrate granivores (birds) and mutualistic interactions with pollinators, including how this is explained by bioclimatic variables. We used both herbarium specimens and field-collected samples to compare phenotypic divergence between continental and island populations. Fruits from island populations were larger than on continents, but the presence of lower spines on mericarps was less frequent on islands. The presence of spines was largely explained by environmental variation among islands. Petal length was on average 9% smaller on island than continental populations, an effect that was especially accentuated on the Galápagos Islands. Our results show that Tribulus cistoides exhibits phenotypic divergence between island and continental habitats for antagonistic traits (seed defense) and mutualistic traits (floral traits). Furthermore, the evolution of phenotypic traits that mediate antagonistic and mutualistic interactions partially depended on the abiotic characteristics of specific islands. This study shows the potential of using a combination of herbarium and field samples for comparative studies on a globally distributed species to study phenotypic divergence on island habitats.

Human-animal interactions from an evolutionary perspective: Symbioses as extended ultrasociality

Abstract The field of human-animal interactions (HAI) is focused primarily on human-companion animal relationships, especially the impact of such relationships on human health. Here, we demonstrate how a wider, integrative approach, consisting of an evolutionary framework, provides new insights into the varieties of HAIs and their emergence and significance during human evolution. Along with other HAI researchers, we show that those HAIs which develop into interrelationships can best be treated as ecological symbioses that involve fitness interdependence among the symbionts and entail the evolution of phenotypic traits that support the adaptive features of the symbionts. We present the novel idea that the formation of mutualistic symbiotic relationships through the process of domestication depended on the prior evolution of hominin hypersociality and ultrasociality in modern humans. Hypersociality was characterized by high levels of social cooperation and social tolerance that became increasingly important for human social life and cooperative hunting. The further development of ultrasociality in modern humans consisted of the development of large-scale (i.e., beyond the hunting band) cooperative social networks of genetically unrelated individuals. This depended on the evolution of further enhancements in socio-cognitive skills, especially representational abilities (e.g., theory of mind), symbolic capacities, and formation of tribal societies with complex social institutions. These modern cognitive and socio-cultural features were made possible by significant brain reorganization during the past 60,000 years. Tribal social institutions were founded on normative moral sentiments and behavior and regulated and ultimately reduced levels of lethal violence. The extension of fitness interdependent, cooperative relationships to large networks of unrelated individuals (i.e., ultrasociality), we argue, was foundational in modern humans to the formation of mutualistic symbioses (i.e., process of domestication) with other animals. Because they are an outgrowth of ultrasociality, we suggest that the term “extended ultrasociality” appropriately describes human interrelationships with domesticated animals. We further suggest that these human-animal interrelationships are unique in that they become imbued with and immersed in our symbolic world, as is demonstrated by the earliest representational art in caves after 50,000 years when enhanced modern human representational and symbolic capacities were evolving. An evolutionary framework invites new questions and avenues for research.

A novel phylogenetic comparative method for evaluating the strength of branch-specific directional selection.

Phylogenetic comparative methods (PCMs) have played a central role in studying the evolution of phenotypic traits. However, when a trait experienced directional selection, previous PCMs have faced a dilemma between mathematically tractable but restrictive models (i.e., simple Gaussian process models) and flexible but intractable approaches (i.e., a simulation-based process model of phenotype evolution built on population genetics frameworks). This paper proposes a novel Gaussian process macroevolutionary model, called the "branch-specific directional selection (BSDS)," for evaluating the strength of directional selection to reconcile these two approaches. This model is based on a second-order approximation of a previous simulation-based process model but has a closed-form likelihood function. This can also be extended to incorporate intraspecies variations and to linear mixed models, which are necessary for meta-analysis. We conduct numerical experiments to validate the proposed method and apply it to the brain volume of Hominidae species. The results show that the proposed methods yield statistically more reliable inferences and computational time is about hundred thousand times faster than the previous simulation-based methods. Further extensions of the BSDS model are expected to provide a clearer picture of the connection of microevolutionary processes and macroevolutionary patterns.

Discovering novel reproductive genes in a non-model fly using de novo GridION transcriptomics.

Gene discovery has important implications for investigating phenotypic trait evolution, adaptation, and speciation. Male reproductive tissues, such as accessory glands (AGs), are hotspots for recruitment of novel genes that diverge rapidly even among closely related species/populations. These genes synthesize seminal fluid proteins that often affect post-copulatory sexual selection-they can mediate male-male sperm competition, ejaculate-female interactions that modify female remating and even influence reproductive incompatibilities among diverging species/populations. Although de novo transcriptomics has facilitated gene discovery in non-model organisms, reproductive gene discovery is still challenging without a reference database as they are often novel and bear no homology to known proteins. Here, we use reference-free GridION long-read transcriptomics, from Oxford Nanopore Technologies (ONT), to discover novel AG genes and characterize their expression in the widespread dung fly, Sepsis punctum. Despite stark population differences in male reproductive traits (e.g.: Body size, testes size, and sperm length) as well as female re-mating, the male AG genes and their secretions of S. punctum are still unknown. We implement a de novo ONT transcriptome pipeline incorporating quality-filtering and rigorous error-correction procedures, and we evaluate gene sequence and gene expression results against high-quality Illumina short-read data. We discover highly-expressed reproductive genes in AG transcriptomes of S. punctum consisting of 40 high-quality and high-confidence ONT genes that cross-verify against Illumina genes, among which 26 are novel and specific to S. punctum. Novel genes account for an average of 81% of total gene expression and may be functionally relevant in seminal fluid protein production. For instance, 80% of genes encoding secretory proteins account for 74% total gene expression. In addition, median sequence similarities of ONT nucleotide and protein sequences match within-Illumina sequence similarities. Read-count based expression quantification in ONT is congruent with Illumina's Transcript per Million (TPM), both in overall pattern and within functional categories. Rapid genomic innovation followed by recruitment of de novo genes for high expression in S. punctum AG tissue, a pattern observed in other insects, could be a likely mechanism of evolution of these genes. The study also demonstrates the feasibility of adapting ONT transcriptomics for gene discovery in non-model systems.

Quantifying (non)parallelism of gut microbial community change using multivariate vector analysis.

Parallel evolution of phenotypic traits is regarded as strong evidence for natural selection and has been studied extensively in a variety of taxa. However, we have limited knowledge of whether parallel evolution of host organisms is accompanied by parallel changes of their associated microbial communities (i.e., microbiotas), which are crucial for their hosts' ecology and evolution. Determining the extent of microbiota parallelism in nature can improve our ability to identify the factors that are associated with (putatively adaptive) shifts in microbial communities. While it has been emphasized that (non)parallel evolution is better considered as a quantitative continuum rather than a binary phenomenon, quantitative approaches have rarely been used to study microbiota parallelism. We advocate using multivariate vector analysis (i.e., phenotypic change vector analysis) to quantify direction and magnitude of microbiota changes and discuss the applicability of this approach for studying parallelism, and we compiled an R package for multivariate vector analysis of microbial communities ('multivarvector'). We exemplify its use by reanalyzing gut microbiota data from multiple fish species that exhibit parallel shifts in trophic ecology. We found that multivariate vector analysis results were largely consistent with other statistical methods, parallelism estimates were not affected by the taxonomic level at which the microbiota is studied, and parallelism might be stronger for gut microbiota function compared to taxonomic composition. This approach provides an analytical framework for quantitative comparisons across host lineages, thereby providing the potential to advance our capacity to predict microbiota changes. Hence, we emphasize that the development and application of quantitative measures, such as multivariate vector analysis, should be further explored in microbiota research in order to better understand the role of microbiota dynamics during their hosts' adaptive evolution, particularly in settings of parallel evolution.

Evolution of predator–prey interactions during range expansion in an aquatic insect predator

Abstract Many ectotherms are shifting their distributions polewards, which has been associated with the evolution of phenotypic traits and their thermal plasticity. Trophic interactions may determine the dynamics and ecological impact of range expansions. However, it is largely unknown how trait evolution in edge populations shapes trophic interactions. We studied evolutionary changes in the short‐term (functional response) and long‐term predator–prey interactions between an aquatic insect predator (the damselfly Ischnura elegans) and its prey (the water flea Daphnia magna) during the predator's ongoing poleward range expansion in northern Europe. Using a common‐garden warming experiment at 20 and 24°C we tested for differentiation between predator populations from edge and core regions in metabolic rate and functional response parameters, and used these empirical data to estimate the effects of range expansion on the short‐ and long‐term predator–prey interaction strengths. Metabolic rates did not differ between populations from edge and core regions nor between rearing temperatures. Functional response parameters and their thermal plasticity showed signals of evolution during the range expansion. Attack rates did not differ between predators from edge and core regions, but only decreased under warming in predators from the edge region. Handling times decreased under warming in predators from the edge region but increased under warming in predators from the core region. While handling times were shorter in predators from the core region at 20°C, these did not differ between regions at 24°C. As a result, the short‐term interaction strength was higher for predators from the core region at 20°C, but not different between regions at 24°C. The predator–prey system from the edge region showed lower long‐term system stability at 20°C, but this region difference disappeared under warming because the edge region stability then increased. Our results suggest that rapid evolution of functional response parameters during a predator's range expansion reduced the direct feeding impact on its prey and made the predator–prey system from the edge region more unstable, but not under warming. This provides rare evidence that functional responses can rapidly evolve during range expansions, potentially destabilizing food web dynamics. Read the free Plain Language Summary for this article on the Journal blog.

Allopatric speciation, niche conservatism and gradual phenotypic change in the evolution of European green lizards

AbstractAimThe contributions of historical biogeography, morphology and climatic niche evolution in shaping species diversification have been typically examined separately. To fill this gap, we assessed the relative role of geologic history, environment and phenotypic trait evolution in lineage diversification of green lizards in the Mediterranean biodiversity hotspot.LocationEurasia and North Africa.TaxonGreen lizards (genera Timon and Lacerta).MethodsFor all green lizard lineages, we characterized distributional ranges and external morphological traits across discrete biogeographical areas, occupied macro‐habitats and climatic niches using environmental variables that represent average and extreme climatic conditions. To assess the contribution of geographical factors in shaping diversity patterns, we evaluated the fit of 24 biogeographical models. We used BAMM and estimated phylogenetic signal to assess the rates of lineage diversification and of phenotypic and climatic niche evolution, and to determine whether these processes occurred steadily or at specific time periods as a response to palaeogeological or palaeoclimatic events. Finally, we tested for associations between phenotypic traits and lineage diversification using trait‐dependent diversification analyses (QuaSSE, ES‐sim and STRAPP).ResultsBiogeographical analyses favoured a dispersal–vicariance model explaining speciation patterns in green lizards, including jump dispersal and constrained dispersal by geographical distance. Lineages accumulated gradually towards the present, with minor divergence in morphological traits and conservatism of climatic niches. In contrast, in the Lacerta agilis lineage, niche evolution may have allowed expansion towards colder environments. Morphological and climatic niche evolution were uncoupled from diversification rates.Main ConclusionsBiogeographical processes largely explain the constant lineage diversification of green lizards in the Mediterranean Basin since the Miocene, followed by gradual phenotypic divergence unrelated to cladogenesis. Climatic niche conservatism promoted the accumulation of lineages within the Mediterranean, except for L. agilis, where climatic niche evolution might underpin its range spread towards higher latitudes.

Evolution of personality and locomotory performance traits during a late Pleistocene island colonization in a tree frog.

Recent empirical and theoretical studies suggest that personality and locomotory performance traits linked to dispersal abilities are crucial components of the dispersal syndromes, and that they can evolve during range expansions and colonization processes. Island colonization is one of the best characterized processes in dispersal biogeography, and its implication in the evolution of phenotypic traits has been investigated over a wide range of temporal scales. However, the effect of island colonization on personality and performance traits of natural populations, and how these traits could drive island colonization, has been little explored. Noteworthy, no studies have addressed these processes in the context of late Pleistocene range expansions. Here, we investigated the contribution of island colonization triggered by postglacial range expansions to intraspecific variation in personality and locomotory performance traits. We compared boldness, exploration, jumping performance, and stickiness abilities in populations from 3 equidistant areas of the Tyrrhenian tree frog Hyla sarda, 2 from the main island (Corsica Island), and 1 from the recently colonized island of Elba. Individuals from Elba were significantly bolder than individuals from Corsica, as they emerged sooner from a shelter (P = 0.028), while individuals from Corsica showed markedly higher jumping and stickiness performance (both P < 0.001), resulting as more performing than those of Elba. We discuss these results in the context of the major microevolutionary processes at play during range expansion, including selection, spatial sorting, founder effects, and their possible interaction with local adaptation processes.

Resource acquisition and pre-copulatory sexual selection.

abstractSexual selection influences the evolution of phenotypic traits and contributes to patterns of biodiversity. In many animals, mating involves sequential steps. Often, individuals must secure resources that are essential for mating (nests, territories, food), and then after securing a resource, individuals engage in competition for access to limited opposite sex mates and gametes. A large body of empirical research and some verbal models have illustrated that resource acquisition can influence sexual selection. In general, though, we lack a priori predictions of when and how resource acquisition will influence sexual selection. Here, we use a mathematical framework to explore the link between resource acquisition and sexual selection on an advantageous mate‐acquisition trait across biologically relevant trade‐off scenarios. Our findings provide a set of testable predictions of how resource acquisition can influence sexual selection on mating traits. In general, selection on mate‐acquisition traits is expected to be heavily influenced by: (1) the episode of selection considered, and in particular, whether one considers selection associated with the mating pool only or selection associated with both the mating pool and pre‐mating pool; (2) whether resource‐acquisition and mate‐acquisition traits are positively associated or whether they trade off; and (3) the proportion of males with the resource‐ and mate‐acquisition traits.

Trophic niche shifts and phenotypic trait evolution are largely decoupled in Australasian parrots

BackgroundTrophic shifts from one dietary niche to another have played major roles in reshaping the evolutionary trajectories of a wide range of vertebrate groups, yet their consequences for morphological disparity and species diversity differ among groups.MethodsHere, we use phylogenetic comparative methods to examine whether the evolution of nectarivory and other trophic shifts have driven predictable evolutionary pathways in Australasian psittaculid parrots in terms of ecological traits such as body size, beak shape, and dispersal capacity.ResultsWe found no evidence for an ‘early-burst’ scenario of lineage or morphological diversification. The best-fitting models indicate that trait evolution in this group is characterized by abrupt phenotypic shifts (evolutionary jumps), with no sign of multiple phenotypic optima correlating with different trophic strategies. Thus, our results point to the existence of weak directional selection and suggest that lineages may be evolving randomly or slowly toward adaptive peaks they have not yet reached.ConclusionsThis study adds to a growing body of evidence indicating that the relationship between avian morphology and feeding ecology may be more complex than usually assumed and highlights the importance of adding more flexible models to the macroevolutionary toolbox.

Hearing loss genes reveal patterns of adaptive evolution at the coding and non-coding levels in mammals

BackgroundMammals possess unique hearing capacities that differ significantly from those of the rest of the amniotes. In order to gain insights into the evolution of the mammalian inner ear, we aim to identify the set of genetic changes and the evolutionary forces that underlie this process. We hypothesize that genes that impair hearing when mutated in humans or in mice (hearing loss (HL) genes) must play important roles in the development and physiology of the inner ear and may have been targets of selective forces across the evolution of mammals. Additionally, we investigated if these HL genes underwent a human-specific evolutionary process that could underlie the evolution of phenotypic traits that characterize human hearing.ResultsWe compiled a dataset of HL genes including non-syndromic deafness genes identified by genetic screenings in humans and mice. We found that many genes including those required for the normal function of the inner ear such as LOXHD1, TMC1, OTOF, CDH23, and PCDH15 show strong signatures of positive selection. We also found numerous noncoding accelerated regions in HL genes, and among them, we identified active transcriptional enhancers through functional enhancer assays in transgenic zebrafish.ConclusionsOur results indicate that the key inner ear genes and regulatory regions underwent adaptive evolution in the basal branch of mammals and along the human-specific branch, suggesting that they could have played an important role in the functional remodeling of the cochlea. Altogether, our data suggest that morphological and functional evolution could be attained through molecular changes affecting both coding and noncoding regulatory regions.

Normal approximation for mixtures of normal distributions and the evolution of phenotypic traits

AbstractExplicit bounds are given for the Kolmogorov and Wasserstein distances between a mixture of normal distributions, by which we mean that the conditional distribution given some $\sigma$ -algebra is normal, and a normal distribution with properly chosen parameter values. The bounds depend only on the first two moments of the first two conditional moments given the $\sigma$ -algebra. The proof is based on Stein’s method. As an application, we consider the Yule–Ornstein–Uhlenbeck model, used in the field of phylogenetic comparative methods. We obtain bounds for both distances between the distribution of the average value of a phenotypic trait over n related species, and a normal distribution. The bounds imply and extend earlier limit theorems by Bartoszek and Sagitov.

Directed genome evolution driven by structural rearrangement techniques.

Directed genome evolution simulates the process of natural evolution at the genomic level in the laboratory to generate desired phenotypes. Here we review the applications of recent technological advances in genome writing and editing to directed genome evolution, with a focus on structural rearrangement techniques. We highlight how these techniques can be used to generate diverse genotypes, and to accelerate the evolution of phenotypic traits. We also discuss the perspectives of directed genome evolution.

The Order of Trait Emergence in the Evolution of Cyanobacterial Multicellularity.

The transition from unicellular to multicellular organisms is one of the most significant events in the history of life. Key to this process is the emergence of Darwinian individuality at the higher level: Groups must become single entities capable of reproduction for selection to shape their evolution. Evolutionary transitions in individuality are characterized by cooperation between the lower level entities and by division of labor. Theory suggests that division of labor may drive the transition to multicellularity by eliminating the trade off between two incompatible processes that cannot be performed simultaneously in one cell. Here, we examine the evolution of the most ancient multicellular transition known today, that of cyanobacteria, where we reconstruct the sequence of ecological and phenotypic trait evolution. Our results show that the prime driver of multicellularity in cyanobacteria was the expansion in metabolic capacity offered by nitrogen fixation, which was accompanied by the emergence of the filamentous morphology and succeeded by a reproductive life cycle. This was followed by the progression of multicellularity into higher complexity in the form of differentiated cells and patterned multicellularity.

Inferring Phenotypic Trait Evolution on Large Trees With Many Incomplete Measurements

Comparative biologists are often interested in inferring covariation between multiple biological traits sampled across numerous related taxa. To properly study these relationships, we must control for the shared evolutionary history of the taxa to avoid spurious inference. An additional challenge arises as obtaining a full suite of measurements becomes increasingly difficult with increasing taxa. This generally necessitates data imputation or integration, and existing control techniques typically scale poorly as the number of taxa increases. We propose an inference technique that integrates out missing measurements analytically and scales linearly with the number of taxa by using a post-order traversal algorithm under a multivariate Brownian diffusion (MBD) model to characterize trait evolution. We further exploit this technique to extend the MBD model to account for sampling error or nonheritable residual variance. We test these methods to examine mammalian life history traits, prokaryotic genomic and phenotypic traits, and HIV infection traits. We find computational efficiency increases that top two orders-of-magnitude over current best practices. While we focus on the utility of this algorithm in phylogenetic comparative methods, our approach generalizes to solve long-standing challenges in computing the likelihood for matrix-normal and multivariate normal distributions with missing data at scale. Supplementary materials for this article are available online.

Genetic diversity and phenotypic variation of the red swamp crayfish, Procambarus clarkii (Girard, 1852) (Decapoda: Astacidea: Astacidae), in China

Abstract The red swamp crayfish, Procambarus clarkii (Girard, 1852), is a paradox in China because it has developed as a popular aquaculture species while becoming a notorious invasive species. We investigated the population genetic diversity and population dynamics of wild Chinese populations of P. clarkii based on proPO fragments and the morphological traits across these populations. The results showed that the populations of P. clarkii exhibit high genetic diversity and significant population structure, inferring that the crayfish was artificially transferred rapidly among different locations for different reasons. Results also revealed distinct phenotypic differentiation, with individuals of some populations having a shorter pleon and wider carapace width, whereas other populations have a small length to width ratio. This study provided comprehensive insights into the population dynamics and morphological variations of P. clarkii, which contribute to understanding the rapid evolution of phenotypic traits after its successful invasion. Results should help establish efficient management strategies for the control of the invasion and at the same time using the genetic information in crayfish aquaculture.

Coping with extremes: convergences of habitat use, territoriality, and diet in summer but divergences in winter between two sympatric snow finches on the Qinghai-Tibet Plateau.

On the Qinghai-Tibet Plateau, extreme environmental conditions have imposed intense selective pressure on the evolution of phenotypic traits of wild animals. To date, limited information is available on behavioral and ecological traits concerning niche differentiation among sympatric animals on the Qinghai-Tibet Plateau, especially during winter when the environments are most severe. Here, we studied the seasonal variations in habitat occurrence, territorial behavior, and diet in two sympatric snow finches (the white-rumped snow finch, Onychostruthus taczanowskii, WRSF; and the rufous-necked snow finch, Pyrgilauda ruficollis, RNSF) to determine convergence and divergence of ecological traits in such severe climatic conditions. Our results showed that: (i) WRSF occupied rural areas as a dominant species throughout the annual cycle while RNSF occupied the rural areas in summer and then shifted to human-occupied areas in winter and spring; (ii) WRSFs exhibited robust aggressive behavior and territoriality during winter relative to RNSFs; (iii) the diets of both species varied with the season but did not vary between species except that WRSF ate significantly more seeds but RNSF consumed more starchy material derived from human food waste during winter. Therefore, the separations in the spatial niche and territoriality between WRSF and RNSF, especially in winter, may contribute to alleviating the pressure of interspecific competition, and promoting the coexistence of the two sympatric snow finches in the extreme environments on the Qinghai-Tibet Plateau.