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1.
    
By constraining gene flow, group living and natal philopatry can result in fine‐scale genetic structure. Although the genetic structure of some group‐living lizards has been characterised, studies are few compared with those for group‐living bird and mammal species. The Egerniinae group of lizards exhibits a high diversity of social structures, making it a useful group for comparative studies of genetic structure across a broader range of social taxa. A well‐studied member of Egerniinae is Egernia stokesii, a lizard that forms long‐term pair bonds and stable social groups and exhibits natal philopatry and limited dispersal. Evidence exists for consistent E. stokesii social structure across seven close but disconnected rocky outcrops within a 40 × 10 km area. We used summary statistics, analysis of molecular variance, Bayesian clustering, and discriminant analysis of principal components to assess if E. stokesii exhibit a consistent pattern of fine‐scale genetic structure across the same seven outcrops. Due to E. stokesii social structure and constrained dispersal, we predicted significant genetic structuring – based on microsatellite markers – among outcrops. We found significant fine‐scale genetic structuring and evidence for two genetic clusters. We discuss features of E. stokesii biology and ecology that may explain our findings. Some rocky outcrops, and some social groups, contained lizards from both genetic clusters. An examination of the composition of mixed cluster social groups did not detect any notable patterns. Therefore, further work is necessary to identify how the observed patterns may have arisen. Future investigations in E. stokesii and other group‐living lizard species are likely to contribute greatly to our understanding of the genetic consequences of group living.  相似文献   

2.
    
Group living often requires strong levels of communication between individuals. This communication is usually studied in the context of visual or auditory communication. However, chemical communication is the most widely used form of communication. We examined the role of chemical communication in mediating social decisions in a group‐living lizard, Egernia stokesii. Specifically, we examined the extent to which scat‐piling, a behaviour by which individuals deposit scat in a communal area, affected the refuge choice of individual E. stokesii. To achieve this, we examined individual refuge choice in response to scat piles or single scats and against two types of scat stimuli, one being their own scat and the other being scat belonging to an unrelated and unfamiliar conspecific. We show that lizards behave differently when presented with a scat pile compared with a single scat, and whether the scat stimulus was their own or sourced from an unfamiliar conspecific. When scats were in piles, individuals spent more time inspecting, more time in, and more often chose the treatment refuge as their final refuge choice, at a trial’s end, when the treatment was their own scat compared with when the treatment was the refuge with the unfamiliar scat. In contrast, for individual scat treatments, individuals spent more time inspecting and more often ended up in the treatment refuge with an unfamiliar scat compared with when the treatment was their own scat. These results suggest that individuals are responding to information contained within multiple components of the scats – both their volume and their source. These results have implications for understanding how social aggregations are maintained within squamates, where sociality has evolved independently from other vertebrate lineages.  相似文献   

3.
    
The evolutionary and adaptive potential of populations or species facing an emerging infectious disease depends on their genetic diversity in genes, such as the major histocompatibility complex (MHC). In birds, MHC class I deals predominantly with intracellular infections (e.g., viruses) and MHC class II with extracellular infections (e.g., bacteria). Therefore, patterns of MHC I and II diversity may differ between species and across populations of species depending on the relative effect of local and global environmental selective pressures, genetic drift, and gene flow. We hypothesize that high gene flow among populations of Humboldt and Magellanic penguins limits local adaptation in MHC I and MHC II, and signatures of selection differ between markers, locations, and species. We evaluated the MHC I and II diversity using 454 next‐generation sequencing of 100 Humboldt and 75 Magellanic penguins from seven different breeding colonies. Higher genetic diversity was observed in MHC I than MHC II for both species, explained by more than one MHC I loci identified. Large population sizes, high gene flow, and/or similar selection pressures maintain diversity but limit local adaptation in MHC I. A pattern of isolation by distance was observed for MHC II for Humboldt penguin suggesting local adaptation, mainly on the northernmost studied locality. Furthermore, trans‐species alleles were found due to a recent speciation for the genus or convergent evolution. High MHC I and MHC II gene diversity described is extremely advantageous for the long‐term survival of the species.  相似文献   

4.
    
Evidence shows that social cooperation among kin may evolve even in birds with extensive dispersal. In such cases, maintaining kinship during dispersal is essential to the subsequent expression of kin cooperation. This hypothesis has not been examined for most bird species. We addressed it in the ground tit (Parus humilis), a passerine where kin frequently interact in terms of cooperative polygamy and extra‐pair mating despite fast annual turnover of the breeding population. Pedigree and genotype data showed that while groups varied in composition throughout the non‐breeding season due to continual individual emigration and immigration, they always contained kin coalitions consisting of either local or immigrant individuals of different age and sexes. The first‐order kin coalitions, according to the information from local individuals, stemmed from single‐family lineages (siblings and their parents), and the lower‐order ones from neighbouring, related family lineages that merged after fledging. It was probable that immigrants had formed kin coalitions in similar ways before dispersing. Groups broke up in the breeding season. Pairing between unrelated individuals from different coalitions within a group was more likely, whereas related individuals from the same coalition tended to nest near each other. The resulting fine‐scale population genetic structure is expected to facilitate breeding interactions among kin. Our findings give clues to understanding the evolution of social cooperation in relation to dispersal.  相似文献   

5.
    
Clonal propagation becomes more abundant with increasing altitudes as environmental conditions worsen. To date, little attention has been paid to the way in which clonal propagation affects genetic diversity and the fine‐scale spatial genetic structure (FSGS) of clonal alpine trees. An AFLP study was undertaken to quantify the clonal and genetic diversity and FSGS of the vulnerable treeline species Polylepis reticulata in Ecuador. We successfully genotyped 32 and 75 ramets within 4 m × 100 m (coarse scale) and 4 m × 4 m (fine scale) transects of one population, respectively. Higher genotypic diversity was detected at the coarse scale than at the fine scale, while lower genetic diversity was detected for P. reticulata than other Polylepis spp. at both scales. Significantly stronger FSGS was detected at the ramet level than the genet level for P. reticulata within a spatial distance of 3 m. The studied P. reticulata population showed pronounced FSGS (Sp = 0.012 at the genet level, a statistic reflecting declining pairwise kinship with distance) revealed restricted gene dispersal, which implies restricted seed dispersal for this population, assuming pollen flow is as extensive as that described for other wind‐pollinated tree species. Our results revealed that clonal diversity is a function of both sample size and the spatial scale of the sampling area. The findings highlights that clonal propagation has affected FSGS within a spatial distance of 3 m for this species.  相似文献   

6.
7.
    
Forest fragmentation may negatively affect plants through reduced genetic diversity and increased population structure due to habitat isolation, decreased population size, and disturbance of pollen‐seed dispersal mechanisms. However, in the case of tree species, effective pollen‐seed dispersal, mating system, and ecological dynamics may help the species overcome the negative effect of forest fragmentation. A fine‐scale population genetics study can shed light on the postfragmentation genetic diversity and structure of a species. Here, we present the genetic diversity and population structure of Cercis canadensis L. (eastern redbud) wild populations on a fine scale within fragmented areas centered around the borders of Georgia–Tennessee, USA. We hypothesized high genetic diversity among the collections of C. canadensis distributed across smaller geographical ranges. Fifteen microsatellite loci were used to genotype 172 individuals from 18 unmanaged and naturally occurring collection sites. Our results indicated presence of population structure, overall high genetic diversity (HE = 0.63, HO = 0.34), and moderate genetic differentiation (FST = 0.14) among the collection sites. Two major genetic clusters within the smaller geographical distribution were revealed by STRUCTURE. Our data suggest that native C. canadensis populations in the fragmented area around the Georgia–Tennessee border were able to maintain high levels of genetic diversity, despite the presence of considerable spatial genetic structure. As habitat isolation may negatively affect gene flow of outcrossing species across time, consequences of habitat fragmentation should be regularly monitored for this and other forest species. This study also has important implications for habitat management efforts and future breeding programs.  相似文献   

8.
    
Despite substantial interest in coevolution's role in diversification, examples of coevolution contributing to speciation have been elusive. Here, we build upon past studies that have shown both coevolution between South Hills crossbills and lodgepole pine (Pinus contorta), and high levels of reproductive isolation between South Hills crossbills and other ecotypes in the North American red crossbill (Loxia curvirostra) complex. We used genotyping by sequencing to generate population genomic data and applied phylogenetic and population genetic analyses to characterize the genetic structure within and among nine of the ecotypes. Although genome‐wide divergence was slight between ecotypes (FST = 0.011–0.035), we found evidence of relative genetic differentiation (as measured by FST) between and genetic cohesiveness within many of them. As expected for nomadic and opportunistic breeders, we detected no evidence of isolation by distance. The one sedentary ecotype, the South Hills crossbill, was genetically most distinct because of elevated divergence at a small number of loci rather than pronounced overall genome‐wide divergence. These findings suggest that mechanisms related to recent local coevolution between South Hills crossbills and lodgepole pine (e.g. strong resource‐based density dependence limiting gene flow) have been associated with genome divergence in the face of gene flow. Our results further characterize a striking example of coevolution driving speciation within perhaps as little as 6000 years.  相似文献   

9.
    
Heritable color polymorphisms have a long history of study in evolutionary biology, though they are less frequently examined today than in the past. These systems, where multiple discrete, visually identifiable color phenotypes co‐occur in the same population, are valuable for tracking evolutionary change and ascertaining the relative importance of different evolutionary mechanisms. Here, we use a combination of citizen science data and field surveys in the Great Lakes region of North America to identify patterns of color morph frequencies in the eastern gray squirrel (Sciurus carolinensis). Using over 68,000 individual squirrel records from both large and small spatial scales, we identify the following patterns: (a) the melanistic (black) phenotype is often localized but nonetheless widespread throughout the Great Lakes region, occurring in all states and provinces sampled. (b) In Ohio, where intensive surveys were performed, there is a weak but significantly positive association between color morph frequency and geographic proximity of populations. Nonetheless, even nearby populations often had radically different frequencies of the melanistic morph, which ranged from 0% to 96%. These patterns were mosaic rather than clinal. (c) In the Wooster, Ohio population, which had over eight years of continuous data on color morph frequency representing nearly 40,000 records, we found that the frequency of the melanistic morph increased gradually over time on some survey routes but decreased or did not change over time on others. These differences were statistically significant and occurred at very small spatial scales (on the order of hundreds of meters). Together, these patterns are suggestive of genetic drift as an important mechanism of evolutionary change in this system. We argue that studies of color polymorphism are still quite valuable in advancing our understanding of fundamental evolutionary processes, especially when coupled with the growing availability of data from citizen science efforts.  相似文献   

10.
    
The spinyhead croaker Collichthys lucidus (Richardson) is a small sciaenid species distributed along the inshore waters of northwestern Pacific Ocean, and now has been listed as Key Protected Commercial Sources of Aquatic Animals and Plants in China. To delineate stock boundaries and inform conservation policy for its management, samples were collected from eight locations across the Chinese coastal waters and analyzed at nine microsatellite loci. C. lucidus populations showed low genetic diversity (expected heterozygosity = 0.445–0.542; observed heterozygosity = 0.392–0.539; Polymorphism Information Content = 0.268–0.684). Strong genetic fdifferentiation (Fst = 0.065–0.510, all significant after Bonferroni correction) among all populations and high levels of self‐recruitment (89.2%–91.5%) were observed, which suggested limited genetic exchange for this species. Clustering results of discriminant analysis of principal components and STRUCTURE found strong support for obvious genetic clusters (populations FZ, XM and SZ vs. populations SH, YRE, ZS, WZ and ND). The results of the present study not only supported the phylogeographic pattern of north‐south differentiation, but also suggested that C. lucidus populations may be predominantly sustained by self‐replenishment rather than by recruitment from distant populations.  相似文献   

11.
    
Comparisons of to can provide insights into the evolutionary processes that lead to differentiation, or lack thereof, among the phenotypes of different groups (e.g., populations, species), and these comparisons have been performed on a variety of taxa, including humans. Here, I show that for neutrally evolving (i.e., by genetic drift, mutation, and gene flow alone) quantitative characters, the two commonly used estimators have somewhat different interpretations in terms of coalescence times, particularly when the number of groups that have been sampled is small. A similar situation occurs for estimators. Consequently, when observations come from only a small number of groups, which is not an unusual situation, it is important to match estimators appropriately when comparing to .  相似文献   

12.
    
The outcome of species interactions may manifest differently at different spatial scales; therefore, our interpretation of observed interactions will depend on the scale at which observations are made. For example, in ladybeetle–aphid systems, the results from small‐scale cage experiments usually cannot be extrapolated to landscape‐scale field observations. To understand how ladybeetle–aphid interactions change across spatial scales, we evaluated predator–prey interactions in an experimental system. The experimental habitat consisted of 81 potted plants and was manipulated to facilitate analysis across four spatial scales. We also simulated a spatially explicit metacommunity model parallel to the experiment. In the experiment, we found that the negative effect of ladybeetles on aphids decreased with increasing spatial scales. This pattern can be explained by ladybeetles strongly suppressing aphids at small scales, but not colonizing distant patches fast enough to suppress aphids at larger scales. In the experiment, the positive effects of aphids on ladybeetles were strongest at three‐plant scale. In a model scenario where predators did not have demographic dynamics, we found, consistent with the experiment, that both the effects of ladybeetles on aphids and the effects of aphids on ladybeetles decreased with increasing spatial scales. These patterns suggest that dispersal was the primary cause of ladybeetle population dynamics in our experiment: aphids increased ladybeetle numbers at smaller scales because ladybeetles stayed in a patch longer and performed area‐restricted searches after encountering aphids; these behaviors did not affect ladybeetle numbers at larger spatial scales. The parallel experimental and model results illustrate how predator–prey interactions can change across spatial scales, suggesting that our interpretation of observed predator–prey dynamics would differ if observations were made at different scales. This study demonstrates how studying ecological interactions at a range of scales can help link the results of small‐scale ecological experiments to landscape‐scale ecological problems.  相似文献   

13.
    
Comparative studies of closely related taxa can provide insights into the evolutionary forces that shape genome evolution and the prevalence of convergent molecular evolution. We investigated patterns of genetic diversity and differentiation in stonechats (genus Saxicola), a widely distributed avian species complex with phenotypic variation in plumage, morphology and migratory behaviour, to ask whether similar genomic regions have become differentiated in independent, but closely related, taxa. We used whole‐genome pooled sequencing of 262 individuals from five taxa and found that levels of genetic diversity and divergence are strongly correlated among different stonechat taxa. We then asked whether these patterns remain correlated at deeper evolutionary scales and found that homologous genomic regions have become differentiated in stonechats and the closely related Ficedula flycatchers. Such correlation across a range of evolutionary divergence and among phylogenetically independent comparisons suggests that similar processes may be driving the differentiation of these independently evolving lineages, which in turn may be the result of intrinsic properties of particular genomic regions (e.g. areas of low recombination). Consequently, studies employing genome scans to search for areas important for reproductive isolation or adaptation should account for corresponding regions of differentiation, as these regions may not necessarily represent speciation islands or evidence of local adaptation.  相似文献   

14.
    
Understanding the drivers of species adaptations to changing environments on the one hand and the limits for hybridization on the other hand is among the hottest questions in evolutionary biology. Parasites represent one of the major selective forces driving host evolution and at least those with free‐living stages are at the same time dependent on the ecological conditions of their host's habitat. Local immunological adaptations of host species to varying parasite pressure are therefore expected and might represent the genetic basis for ecological speciation and the maintenance of recently diverged species. Madagascar provides one of the rare examples where two partially sympatric primate species (Microcebus griseorufus, M. murinus) and their hybrids, as well as an allopatric species (M. cf rufus) live in close proximity along a very steep environmental gradient ranging from southern dry spiny bush to gallery forest to evergreen eastern humid rain forest, thus mimicking the situation encountered during extensions and retreats of vegetation formations under changing climatic conditions. This system was used to study parasite infection and immune gene (MHC) adaptations to varying parasite pressure that might provide selective advantages to pure species over hybrids. Parasite burdens increased with increasing humidity. M. griseorufus, M. murinus, and their hybrids but not M. rufus shared the same MHC alleles, indicating either retention of ancestral polymorphism or recent gene flow. The hybrids had much higher prevalence of intestinal parasites than either of the parent species living under identical environmental conditions. The different representation of parasites can indicate a handicap for hybrids that maintains species identities.  相似文献   

15.
    
Temperature is one of the most important environmental parameters with crucial impacts on nearly all biological processes. Due to anthropogenic activity, average air temperatures are expected to increase by a few degrees in coming decades, accompanied by an increased occurrence of extreme temperature events. Such global trends are likely to have various major impacts on human society through their influence on natural ecosystems, food production and biotic interactions, including diseases. In this study, we used a combination of statistical genetics, experimental evolution and common garden experiments to investigate the evolutionary potential for thermal adaptation in the potato late blight pathogen, Phytophthora infestans, and infer its likely response to changing temperatures. We found a trade‐off associated with thermal adaptation to heterogeneous environments in P. infestans, with the degree of the trade‐off peaking approximately at the pathogen's optimum growth temperature. A genetic trade‐off in thermal adaptation was also evidenced by the negative association between a strain's growth rate and its thermal range for growth, and warm climates selecting for a low pathogen growth rate. We also found a mirror effect of phenotypic plasticity and genetic adaptation on growth rate. At below the optimum, phenotypic plasticity enhances pathogen's growth rate but nature selects for slower growing genotypes when temperature increases. At above the optimum, phenotypic plasticity reduces pathogen's growth rate but natural selection favours for faster growing genotypes when temperature increases further. We conclude from these findings that the growth rate of P. infestans will only be marginally affected by global warming.  相似文献   

16.
    
Positive selection not only increases beneficial allele frequency but also causes augmentation of allele frequencies of sequence variants in close proximity. Signals for positive selection were detected by the statistical differences in subsequent allele frequencies. To identify selection signatures in Korean cattle, we applied a composite log‐likelihood (CLL)‐based method, which calculates a composite likelihood of the allelic frequencies observed across sliding windows of five adjacent loci and compares the value with the critical statistic estimated by 50 000 permutations. Data for a total of 11 799 nucleotide polymorphisms were used with 71 Korean cattle and 209 foreign beef cattle. As a result, 147 signals were identified for Korean cattle based on CLL estimates (< 0.01). The signals might be candidate genetic factors for meat quality by which the Korean cattle have been selected. Further genetic association analysis with 41 intragenic variants in the selection signatures with the greatest CLL for each chromosome revealed that marbling score was associated with five variants. Intensive association studies with all the selection signatures identified in this study are required to exclude signals associated with other phenotypes or signals falsely detected and thus to identify genetic markers for meat quality.  相似文献   

17.
Sexual selection involving genetically disassortative mate choice is one of several evolutionary processes that can maintain or enhance population genetic variability. Examples of reproductive systems in which choosers (generally females) select mates depending on their major histocompatibility complex (MHC) genes have been reported for several vertebrate species. Notably, the role of MHC‐dependent choice not in mating contexts, but in other kinds of social interactions such as in the establishment of complex social systems, has not yet drawn significant scientific interest and is virtually absent from the literature. We have investigated male and female MHC‐dependent choice in an invasive population of North American raccoons (Procyon lotor) in Germany. Both male and female raccoons rely on olfaction for individual recognition. Males have an unusually complex social system in which older individuals choose unrelated younger ones to form stable male coalitions that defend territories and a monopoly over females. We have confirmed that females perform MHC‐disassortative mate choice and that this behaviour fosters genetic diversity of offspring. We have also observed that males build coalitions by choosing male partners depending on their MHC, but in an assortative manner. This is the first observation of antagonistic MHC‐dependent behaviours among sexes. We show that this is the only combination of MHC‐dependent partner choice that leads to outbreeding. In the case of introduced raccoons, such behaviours can act together to promote the invasive potential of the species by increasing its adaptive genetic divergence.  相似文献   

18.
    
Fungal endophytes have been documented in almost all terrestrial plant groups. Although the endophyte infection syndrome in agronomic cultivars is well studied, relatively little work addresses questions of spatial ecology and fire effects on epichloae endophyte infection in native grasses, and none, to our knowledge, in sub‐Saharan Africa. We sampled seven populations of the native Festuca costata Nees along the spline of the Drakensberg range in South Africa at several spatial scales, including both recently burned and unburned stands. We tested epichloae presence and prevalence with immunoblot assays, PCR and genetic sequencing. We found epichloae endophytes were present and prevalent (38–98% infection rates depending on location). Variation in infection rates occurred primarily among locations, but also among bunches. There was little evidence that endophyte infection rates varied with fire. Novel evidence of epichloae infection of a native Festuca in South Africa opens the door to several new research questions, from the phylogenetic relationship between epichloae of sub‐Saharan Africa and other continents to the ecological advantages or disadvantages that endophytes confer upon their hosts, especially in a fire‐prone ecosystem vulnerable to global environmental change.  相似文献   

19.
    
Freshwater green microalgae are diverse and widely distributed across the globe, yet the population structuring of these organisms is poorly understood. We assessed the degree of genetic diversity and differentiation of the desmid species, Micrasterias rotata. First, we compared the sequences of four nuclear regions (actin, gapC1, gapC2, and oee1) in 25 strains and selected the gapC1 and actin regions as the most appropriate markers for population structure assessment in this species. Population genetic structure was subsequently analyzed, based on seven populations from the Czech Republic and Ireland. Hudson's Snn statistics indicated that nearest‐neighbor sequences occurred significantly more frequently within geographical populations than within the wider panmictic population. Moreover, Irish populations consistently showed higher genetic diversity than the Czech samples. These results are in accordance with the unbalanced distribution of alleles in many land plant species; however, the large genetic diversity in M. rotata differs from levels of genetic diversity found in most land plants.  相似文献   

20.
    
The capacity of restored plant populations to adapt to new environmental challenges depends on within‐population genetic variation. We examined how much genetic and environmentally based variation for fitness‐associated traits exists within populations of two native grasses commonly used for restoration in California. We were also interested in understanding how phenotypic expression of genetic variation for these traits varies with growth environment. Thirty maternal families of Elymus glaucus (Blue wild rye) and Nassella pulchra (Purple needlegrass) were sampled from both coastal and interior populations and reciprocally transplanted into three replicated common gardens with and without interspecific competition at each site. Reproductive output of families differed both among years and with competition treatments. Phenotypic expression of genetic variation in culm production differed among populations and was very low when families were grown with interspecific competition. Without interspecific competition, the degree of genetic determination peaked in year two in both species (8.4 and 15.1% in E. glaucus and N. pulchra, respectively). Significant genetic differences in reproduction and phenotypic plasticity were found among N. pulchra subpopulations sampled less than 3 km apart, further highlighting the importance of thoroughly sampling available genetic variation in populations used for restoration. The variable and generally low expression of genetic variation indicates that rates of adaptation in restored populations of these native grasses may vary temporally and may be especially slow within competitive environments.  相似文献   

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