共查询到20条相似文献,搜索用时 31 毫秒
1.
This study assessed the genotype by environment (G × E) interaction for diameter growth in 15 Eucalyptus globulus progeny trials in Australia. Single-site analyses revealed significant subrace and family-within-subrace variance in all trials. Across-site subrace () and family () correlations were estimated by linear mixed model analyses of pairs of trials. Using a factor analytic structure for subrace and family random terms in a multi-environment mixed model analysis, best linear unbiased predictions of subrace effects were obtained for each trial. These were then averaged for each of four states (Victoria, Tasmania, South Australia and Western Australia) and across all sites. Statistically significant G × E interaction was detected, and weighted means across states for and were 0.73 and 0.76, respectively. Nevertheless, the three subraces from the Otway Ranges were both fast growing and relatively stable in their ranks over all sites. We evaluated the sensitivity of subraces to changing environmental conditions, on the basis of random coefficient models regressing subrace performance on selected trial climatic variables. The results suggested differential susceptibility of subraces to water, light and (to a less extent) temperature stresses during summer. Moreover, using multivariate techniques to visualize and interpret the across-site correlation structure for subrace effects, we could identify site clusters of reduced G × E interaction related to soil water availability and evaporative demand during summer. A revised site-type classification using these factors should allow a better capture of genetic gains from breeding and deployment. 相似文献
2.
Desmond J. Stackpole René E. Vaillancourt Marcelo de Aguigar Brad M. Potts 《Tree Genetics & Genomes》2010,6(2):179-193
Genetic parameters for stem diameter and wood density were compared at selection (4–5 years) and harvest (16–17 years) age
in an open-pollinated progeny trial of Eucalyptus globulus in Tasmania (Australia). The study examined 514 families collected from 17 subraces of E. globulus. Wood density was assessed on a subsample of trees indirectly using pilodyn penetration at both ages and directly by core
basic density at harvest age. Significant additive genetic variance and narrow-sense heritabilities (
h\textop2 h_{\text{op}}^2 ) were detected for all traits. Univariate and multivariate estimates of heritabilities were similar for each trait except
harvest-age diameter. Comparable univariate estimates of selection- and harvest-age heritabilities for diameter masked changes
in genetic architecture that occurred with stand development, whereby the loss of additive genetic variance through size-dependent
mortality was countered by the accentuation of additive genetic differences among survivors with age. Regardless, the additive
genetic (r
a) and subrace (r
s) correlations across ages were generally high for diameter (0.95 and 0.61, respectively) and pilodyn penetration (0.77 and
0.96), as were the correlations of harvest-age core basic density with selection- and harvest-age pilodyn (r
a −0.83, −0.88; r
s −0.96, −0.83). While r
s between diameter and pilodyn were close to zero at both ages, there was a significant change in r
a from adverse at selection age (0.25) to close to zero (−0.07) at harvest age. We argue that this change in the genetic correlation
reflects a decoupling of the genetic association of growth and wood density with age. This result highlights the need to validate
the use of selection-age genetic parameters for predicting harvest-age breeding values. 相似文献
3.
Emily H. Le Sage Sarah I. Duncan Travis Seaborn Jennifer Cundiff Leslie J. Rissler Erica J. Crespi 《Heredity》2021,126(5):790
Phenotypic variation among populations is thought to be generated from spatial heterogeneity in environments that exert selection pressures that overcome the effects of gene flow and genetic drift. Here, we tested for evidence of isolation by distance or by ecology (i.e., ecological adaptation) to generate variation in early life history traits and phenotypic plasticity among 13 wood frog populations spanning 1200 km and 7° latitude. We conducted a common garden experiment and related trait variation to an ecological gradient derived from an ecological niche model (ENM) validated to account for population density variation. Shorter larval periods, smaller body weight, and relative leg lengths were exhibited by populations with colder mean annual temperatures, greater precipitation, and less seasonality in precipitation and higher population density (high-suitability ENM values). After accounting for neutral genetic variation, the QST–FST analysis supported ecological selection as the key process generating population divergence. Further, the relationship between ecology and traits was dependent upon larval density. Specifically, high-suitability/high-density populations in the northern part of the range were better at coping with greater conspecific competition, evidenced by greater postmetamorphic survival and no difference in body weight when reared under stressful conditions of high larval density. Our results support that both climate and competition selection pressures drive clinal variation in larval and metamorphic traits in this species. Range-wide studies like this one are essential for accurate predictions of population’s responses to ongoing ecological change.Subject terms: Biogeography, Ecological modelling, Evolutionary ecology, Evolution 相似文献
4.
Julianne M. O’Reilly-Wapstra Alison M. Miller Matthew G. Hamilton Dean Williams Naomi Glancy-Dean Brad M. Potts 《PloS one》2013,8(3)
Understanding among and within population genetic variation of ecologically important plant traits provides insight into the potential evolutionary processes affecting those traits. The strength and consistency of selection driving variability in traits would be affected by plasticity in differences among genotypes across environments (G×E). We investigated population divergence, selection and environmental plasticity of foliar plant secondary metabolites (PSMs) in a dominant tree species, Eucalyptus globulus. Using two common garden trials we examined variation in PSMs at multiple genetic scales; among 12 populations covering the full geographic range of the species and among up to 60 families within populations. Significant genetic variation in the expression of many PSMs resides both among and within populations of E. globulus with moderate (e.g., sideroxylonal A h2op = 0.24) to high (e.g., macrocarpal G h2op = 0.48) narrow sense heritabilities and high coefficients of additive genetic variation estimated for some compounds. A comparison of Qst and Fst estimates suggest that variability in some of these traits may be due to selection. Importantly, there was no genetic by environment interaction in the expression of any of the quantitative chemical traits despite often significant site effects. These results provide evidence that natural selection has contributed to population divergence in PSMs in E. globulus, and identifies the formylated phloroglucinol compounds (particularly sideroxylonal) and a dominant oil, 1,8-cineole, as candidates for traits whose genetic architecture has been shaped by divergent selection. Additionally, as the genetic differences in these PSMs that influence community phenotypes is stable across environments, the role of plant genotype in structuring communities is strengthened and these genotypic differences may be relatively stable under global environmental changes. 相似文献
5.
Dorothy A. Steane Natalie Conod Rebecca C. Jones René E. Vaillancourt Bradley M. Potts 《Tree Genetics & Genomes》2006,2(1):30-38
Eucalyptus globulus (Myrtaceae) is a forest tree native to southeastern Australia, but is grown globally for pulpwood and timber. Eight microsatellite
loci were used to determine the degree of selectively neutral differentiation between native populations of the geographic
races of E. globulus that are used in a national breeding programme. Spatial differentiation was detected among 340 samples from across the species
range (F
ST=0.09±0.02). Analysis of molecular variance showed that there was significant variation between the races, and an unweighted
pair group method with arithmetic mean analysis of Nei’s genetic distance between races showed that geographically proximal
races tended to be more closely related than geographically distant races. This contrasted markedly with analyses based on
quantitative genetic data, where some races appeared to be highly divergent from their geographically closest neighbours.
Comparison of racial differentiation based on quantitative (Q
ST) and molecular (F
ST) data suggested that at least five of the quantitative traits used for defining races of E. globulus have been influenced by natural selection, resulting in cases of both phenotypic divergence of parapatric races and phenotypic
convergence of allopatric races. We conclude that selectively neutral molecular markers are more useful than quantitative
genetic data for identifying the evolutionary affinities and lineages within E. globulus. However, both sources of information should be used in defining evolutionarily important units for conservation. The population
structure observed in E. globulus has important consequences for future association studies and may also affect breeding strategies if significant genome co-adaptation
has occurred. 相似文献
6.
Genetic differentiation along environmental clines is often observed as a result of interplay between gene flow and natural
selection. In order to understand the relative roles of these processes in shaping this differentiation, we designed a study
in which we used two approaches that have not previously been combined, the Q
ST–F
ST comparison and crossbreeding. We examined (1) interpopulation phenotypic and genetic (AFLP) variation, and (2) performance
of interpopulation hybrids in a common annual Senecio glaucus. Fitness of interpopulation hybrids (F1 and F2) was tested under simulated population natural conditions in terms of aridity
and analyzed for a relationship with (1) spatial distance and (2) environmental differences (amount of annual rainfall). While
phenotypic variation corresponded to the clinal changes in aridity along population locations, viz. narrower and longer leaves,
longer leaf outgrowths and advanced flowering in more arid environments, the F
ST < 0.1 calculated from AFLP data suggested intensive interpopulation gene flow, with little if any contribution of genetic
drift. Performance of hybrids in simulated natural environments revealed heterosis in F1, but a hybrid breakdown in F2 generation.
These effects were related to both the spatial distance between hybrid parents and their population rainfall differences.
The detected clinal phenotypic variation and outbreeding depression in F2 strongly support presence of aridity-induced clinal
natural selection, which is matched by the observed Q
ST ≫ F
ST. From this we conclude that Q
ST–F
ST comparison can detect effect of diversifying selection when patterns of phenotypic variation across sampled locations can
be reliably predicted from environmental variation. 相似文献
7.
Soumaya Arraouadi Mounawer Badri Cheruth Abdul Jaleel Naceur Djébali Houcine Ilahi Thierry Huguet Mohamed Elarbi Aouani 《Tropical plant biology》2009,2(3-4):122-132
We used 19 quantitative traits and 14 microsatellite markers (SSRs) to analyze the genetic variation in four natural populations of the model legume Medicago truncatula sampled in southern Tunisia. The greatest genetic variation of quantitative traits and molecular markers occurred within populations (>71%). In contrast to quantitative population differentiation (Q ST ?=?0.09), a high level of molecular differentiation (F ST ?=?0.23) was found among populations. The majority of quantitative traits exhibited Q ST values significantly less than F ST values, suggesting that selection may be acting to suppress differentiation for these traits. There was no significant correlation between genetic variation of quantitative traits and molecular markers within populations. On the other hand, significant correlations were found between measured quantitative characters and the site-of-origin environmental factors. The eco-geographical factors with the greatest influence on the variation of measured traits among populations were altitude, followed by soil texture, assimilated phosphorus (P2O5) and organic matter. Nevertheless, there were no consistent patterns of associations between gene diversity (He) and eco-geographical factors. 相似文献
8.
Nicolas-George Homer Eliades Oliver Gailing Ludger Leinemann Bruno Fady Reiner Finkeldey 《Plant Systematics and Evolution》2011,294(3-4):185-198
Endemic island plant species with a narrow distribution are often, but not always, linked to low genetic variation within populations and a lack of differentiation among populations. Cedrus brevifolia is a narrow endemic island tree species of Cyprus. Its range is restricted to a single forest, divided into five neighbouring sites. This study, using biparentally inherited nuclear microsatellites and paternally inherited plastid (chloroplast) microsatellites, assessed the genetic variation of C. brevifolia within its sole population and the level of genetic differentiation among formed sites. The results from both markers showed high diversity (nuclear H T?=?0.70; plastid H T?=?0.93), strongly suggesting that the species did not experience severe bottleneck events or extensive genetic drift. Besides, the maintenance of a high genetic diversity in C. brevifolia may suggest that it originates from a widespread congener species. Significant genetic differentiation at nuclear (G ST?=?0.052) and plastid (G ST?=?0.119) markers was found among the formed sites. Remarkably, the relatively high genetic differentiation found at plastid markers was comparable to values observed in two widespread congener cedar species. The genetic differentiation probably occurred due to fragmentation of a previously uniform population. This would lead to the shaping of different genetic groups (Bayesian analysis) and to significant population substructure. Furthermore, significant values observed for both isolation by distance and large-scale spatial genetic structure could indicate ineffective gene flow among sites and the early geographical isolation of the more isolated sites from the core population. 相似文献
9.
Hans Ammitzboll René E. Vaillancourt Brad M. Potts Peter A. Harrison Tim Brodribb Frances C. Sussmilch Jules S. Freeman 《Plant, cell & environment》2020,43(1):103-115
Drought is a major stress impacting forest ecosystems worldwide. We utilized quantitative trait loci (QTL) analysis to study the genetic basis of variation in (a) drought resistance and recovery and (b) candidate traits that may be associated with this variation in the forest tree Eucalyptus globulus. QTL analysis was performed using a large outcrossed F2 mapping population from which 300 trees were phenotyped based on the mean performance of their open-pollinated F3 progeny. Progenies were grown in a glasshouse in a randomized complete block design. A subset of seedlings was subjected to a drought treatment after which they were rewatered and scored for damage and growth postdrought. Nondroughted seedlings were assessed for growth traits as well as lignotuber size and resprouting following severe damage to the main stem. QTL were detected for most traits. Importantly, independent QTL were detected for (a) drought damage and plant size, (b) drought damage and growth recovery, and (c) lignotuber size and resprouting capacity. Such independence argues that trade-offs are unlikely to be a major limitation to the response to selection and at the early life history stage studied; there are opportunities to improve resilience to drought without adverse effects on productivity. 相似文献
10.
Rosana López Unai López de Heredia Carmen Collada Francisco Javier Cano Brent C. Emerson Hervé Cochard Luis Gil 《Annals of botany》2013,111(6):1167-1179
Background and Aims
It is widely accepted that hydraulic failure due to xylem embolism is a key factor contributing to drought-induced mortality in trees. In the present study, an attempt is made to disentangle phenotypic plasticity from genetic variation in hydraulic traits across the entire distribution area of a tree species to detect adaptation to local environments.Methods
A series of traits related to hydraulics (vulnerability to cavitation and hydraulic conductivity in branches), growth performance and leaf mass per area were assessed in eight Pinus canariensis populations growing in two common gardens under contrasting environments. In addition, the neutral genetic variability (FST) and the genetic differentiation of phenotypic variation (QST) were compared in order to identify the evolutionary forces acting on these traits.Key Results
The variability for hydraulic traits was largely due to phenotypic plasticity. Nevertheless, the vulnerability to cavitation displayed a significant genetic variability (approx. 5 % of the explained variation), and a significant genetic × environment interaction (between 5 and 19 % of the explained variation). The strong correlation between vulnerability to cavitation and survival in the xeric common garden (r = –0·81; P < 0·05) suggests a role for the former in the adaptation to xeric environments. Populations from drier sites and higher temperature seasonality were less vulnerable to cavitation than those growing at mesic sites. No trade-off between xylem safety and efficiency was detected. QST of parameters of the vulnerability curve (0·365 for P50 and the slope of the vulnerability curve and 0·452 for P88) differed substantially from FST (0·091), indicating divergent selection. In contrast, genetic drift alone was found to be sufficient to explain patterns of differentiation for xylem efficiency and growth.Conclusions
The ability of P. canariensis to inhabit a wide range of ecosystems seemed to be associated with high phenotypic plasticity and some degree of local adaptations of xylem and leaf traits. Resistance to cavitation conferred adaptive potential for this species to adapt successfully to xeric conditions. 相似文献11.
Background
Cavitation resistance to water stress-induced embolism determines plant survival during drought. This adaptive trait has been described as highly variable in a wide range of tree species, but little is known about the extent of genetic and phenotypic variability within species. This information is essential to our understanding of the evolutionary forces that have shaped this trait, and for evaluation of its inclusion in breeding programs.Methodology
We assessed cavitation resistance (P 50), growth and carbon isotope composition in six Pinus pinaster populations in a provenance and progeny trial. We estimated the heritability of cavitation resistance and compared the distribution of neutral markers (F ST) and quantitative genetic differentiation (Q ST), for retrospective identification of the evolutionary forces acting on these traits.Results/Discussion
In contrast to growth and carbon isotope composition, no population differentiation was found for cavitation resistance. Heritability was higher than for the other traits, with a low additive genetic variance (h2 ns = 0.43±0.18, CVA = 4.4%). Q ST was significantly lower than F ST, indicating uniform selection for P 50, rather than genetic drift. Putative mechanisms underlying QST12.
Rebecca C. Jones Dorothy A. Steane Martyn Lavery René E. Vaillancourt Brad M. Potts 《Ecology and evolution》2013,3(1):1-17
Forest trees frequently form species complexes, complicating taxonomic classification and gene pool management. This is certainly the case in Eucalyptus, and well exemplified by the Eucalyptus globulus complex. This ecologically and economically significant complex comprises four taxa (sspp. bicostata, globulus, maidenii, pseudoglobulus) that are geographically and morphologically distinct, but linked by extensive “intergrade” populations. To resolve their genetic affinities, nine microsatellites were used to genotype 1200 trees from throughout the natural range of the complex in Australia, representing 33 morphological core and intergrade populations. There was significant spatial genetic structure (FST = 0.10), but variation was continuous. High genetic diversity in southern ssp. maidenii indicates that this region is the center of origin. Genetic diversity decreases and population differentiation increases with distance from this area, suggesting that drift is a major evolutionary process. Many of the intergrade populations, along with other populations morphologically classified as ssp. pseudoglobulus or ssp. globulus, belong to a “cryptic genetic entity” that is genetically and geographically intermediate between core ssp. bicostata, ssp. maidenii, and ssp. globulus. Geography, rather than morphology, therefore, is the best predictor of overall genetic affinities within the complex and should be used to classify germplasm into management units for conservation and breeding purposes. 相似文献
13.
Mamadou Dia Sow Vincent Segura Sylvain Chamaillard Véronique Jorge Alain Delaunay Clément Lafon-Placette Régis Fichot Patricia Faivre-Rampant Marc Villar Franck Brignolas Stéphane Maury 《Tree Genetics & Genomes》2018,14(5):78
In a context of climate change and forest decline, a better understanding of the sources of tree flexibility involved in phenotypic plasticity and adaptation is needed. These last years, the role of epigenetics in the response to environmental variations has been established in several model plants at the genotype level but little is known at the level of natural populations grown in pedoclimatic sites. Here, we focused on three French natural populations of black poplar, a key pioneer tree from watersheds, planted in common garden and subjected to controlled variations of water availability. We estimated common genetic parameters such as narrow-sense heritability (h2), phenotypic differentiation index (PST), and the overall genetic differentiation index (FST) from genome-wide SNPs to evaluate the extent of epigenetic variations. Indeed, global DNA methylation levels from individuals exposed to drought or irrigated in a common garden were used. We found that the three populations were not distinguished by their levels of DNA methylation. However, a moderate drought was associated to a significant decrease in DNA methylation in the populations. Narrow-sense heritability and PST estimates of DNA methylation were similar to those found for biomass productivity. Heritability and PST were higher when trees were subjected to drought than in control condition. Negative genetic correlations between global DNA methylation and height or biomass were detected in drought condition only. Altogether, our data highlight that global DNA methylation acts as a genetic marker of natural population differentiation under drought stress in a pedoclimatic context. 相似文献
14.
Resistance of insects to insecticides is often associated with reduced fitness in the absence of selection. We examined fitness trade-offs associated with resistance to the microbial insecticide, Bacillus thuringiensis (Bt), across full-sib families in a resistant population of Trichoplusia ni. Significant genetic variation in and heritability of susceptibility to Bt occurred among the full-sib families. Male pupal weight was positively correlated with Bt susceptibility, indicating a potential fitness cost, but no such correlation occurred for females. Significant heritability for pupal weight was present for males but not females. A significant negative genetic correlation existed between development time and Bt susceptibility, indicating that resistant larvae developed more slowly than susceptible larvae. Selection for Bt resistance in T. ni resulted in changes in life-history traits that affected males more than females. 相似文献
15.
Detecting local adaptation and its spatial scale is one of the most important questions of evolutionary biology. However, recognition of the effect of local selection can be challenging when there is considerable environmental variation across the distance at the whole species range. We analyzed patterns of local adaptation in emmer wheat, Triticum dicoccoides, at two spatial scales, small (inter-population distance less than one km) and large (inter-population distance more than 50 km) using several approaches. Plants originating from four distinct habitats at two geographic scales (cold edge, arid edge and two topographically dissimilar core locations) were reciprocally transplanted and their success over time was measured as 1) lifetime fitness in a year of planting, and 2) population growth four years after planting. In addition, we analyzed molecular (SSR) and quantitative trait variation and calculated the QST/FST ratio. No home advantage was detected at the small spatial scale. At the large spatial scale, home advantage was detected for the core population and the cold edge population in the year of introduction via measuring life-time plant performance. However, superior performance of the arid edge population in its own environment was evident only after several generations via measuring experimental population growth rate through genotyping with SSRs allowing counting the number of plants and seeds per introduced genotype per site. These results highlight the importance of multi-generation surveys of population growth rate in local adaptation testing. Despite predominant self-fertilization of T. dicoccoides and the associated high degree of structuring of genetic variation, the results of the QST - FST comparison were in general agreement with the pattern of local adaptation at the two spatial scales detected by reciprocal transplanting. 相似文献
16.
Ana Hernández-Serrano Miguel Verdú Luís Santos-del-Blanco José Climent Santiago C. González-Martínez Juli G. Pausas 《Annals of botany》2014,114(3):571-577
Background and Aims
Although it is well known that fire acts as a selective pressure shaping plant phenotypes, there are no quantitative estimates of the heritability of any trait related to plant persistence under recurrent fires, such as serotiny. In this study, the heritability of serotiny in Pinus halepensis is calculated, and an evaluation is made as to whether fire has left a selection signature on the level of serotiny among populations by comparing the genetic divergence of serotiny with the expected divergence of neutral molecular markers (QST–FST comparison).Methods
A common garden of P. halepensis was used, located in inland Spain and composed of 145 open-pollinated families from 29 provenances covering the entire natural range of P. halepensis in the Iberian Peninsula and Balearic Islands. Narrow-sense heritability (h2) and quantitative genetic differentiation among populations for serotiny (QST) were estimated by means of an ‘animal model’ fitted by Bayesian inference. In order to determine whether genetic differentiation for serotiny is the result of differential natural selection, QST estimates for serotiny were compared with FST estimates obtained from allozyme data. Finally, a test was made of whether levels of serotiny in the different provenances were related to different fire regimes, using summer rainfall as a proxy for fire regime in each provenance.Key Results
Serotiny showed a significant narrow-sense heritability (h2) of 0·20 (credible interval 0·09–0·40). Quantitative genetic differentiation among provenances for serotiny (QST = 0·44) was significantly higher than expected under a neutral process (FST = 0·12), suggesting adaptive differentiation. A significant negative relationship was found between the serotiny level of trees in the common garden and summer rainfall of their provenance sites.Conclusions
Serotiny is a heritable trait in P. halepensis, and selection acts on it, giving rise to contrasting serotiny levels among populations depending on the fire regime, and supporting the role of fire in generating genetic divergence for adaptive traits. 相似文献17.
Genetic drift and selection are ubiquitous evolutionary forces acting to shape genetic variation in populations. While their relative importance has been well studied in plants and animals, less is known about their relative importance in fungal pathogens. Because agro-ecosystems are more homogeneous environments than natural ecosystems, stabilizing selection may play a stronger role than genetic drift or diversifying selection in shaping genetic variation among populations of fungal pathogens in agro-ecosystems. We tested this hypothesis by conducting a Q
ST/F
ST analysis using agricultural populations of the barley pathogen Rhynchosporium commune. Population divergence for eight quantitative traits (Q
ST) was compared with divergence at eight neutral microsatellite loci (F
ST) for 126 pathogen strains originating from nine globally distributed field populations to infer the effects of genetic drift and types of selection acting on each trait. Our analyses indicated that five of the eight traits had Q
ST values significantly lower than F
ST, consistent with stabilizing selection, whereas one trait, growth under heat stress (22°C), showed evidence of diversifying selection and local adaptation (Q
ST>F
ST). Estimates of heritability were high for all traits (means ranging between 0.55–0.84), and average heritability across traits was negatively correlated with microsatellite gene diversity. Some trait pairs were genetically correlated and there was significant evidence for a trade-off between spore size and spore number, and between melanization and growth under benign temperature. Our findings indicate that many ecologically and agriculturally important traits are under stabilizing selection in R. commune and that high within-population genetic variation is maintained for these traits. 相似文献
18.
Jean-Baptiste Lamy Frédéric Lagane Christophe Plomion Hervé Cochard Sylvain Delzon 《Plant Ecology》2012,213(11):1781-1792
Wood density can be considered an adaptive trait, because it ensures the safe and efficient transport of water from the roots to the leaves, mechanical support for the body of the plant and the storage of biological chemicals. Its variability has been extensively described in narrow genetic backgrounds and in wide ranges of forest tree species, but little is known about the extent of natural genetic and phenotypic variability within species. This information is essential to our understanding of the evolutionary forces that have shaped this trait, and for the evaluation of its inclusion in breeding programs. We assessed juvenile wood density, leaf area, total aboveground biomass, and growth in six Pinus pinaster populations of different geographic origins (France, Spain, and Morocco) growing in a provenance-progeny trial. No genetic differentiation was found for wood density, whereas all other traits significantly differed between populations. Heritability of this trait was moderate, with a low additive genetic variance. For retrospective identification of the evolutionary forces acting on juvenile wood density, we compared the distribution of neutral markers (F ST) and quantitative genetic differentiation (Q ST). We found that Q ST was significantly lower than F ST, suggesting evolutionary stasis. Furthermore, we did not detect any relationship between juvenile wood density and drought tolerance (resistance to cavitation), suggesting that this trait could not be used as a proxy for drought tolerance at the intraspecific level. 相似文献
19.
Studies linking genetic structure in amphibian species with ecological characteristics have focused on large differences in dispersal capabilities. Here, we test whether two species with similar dispersal potential but subtle differences in other ecological characteristics also exhibit strong differences in genetic structure in the same landscape. We examined eight microsatellites in marbled salamanders (Ambystoma opacum) from 29 seasonal ponds and spotted salamanders (Ambystoma maculatum) from 19 seasonal ponds in a single geographic region in west-central Massachusetts. Despite overall similarity in ecological characteristics of spotted and marbled salamanders, we observed clear differences in the genetic structure of these two species. For marbled salamanders, we observed strong overall genetic differentiation (F ST = 0.091, F′ ST = 0.375), three population-level clusters of populations (K = 3), a strong pattern of isolation by distance (r = 0.58), and marked variation in family-level structure (from 1 to 23 full-sibling families per site). For spotted salamanders, overall genetic differentiation was weaker (F ST = 0.025, F′ ST = 0.102), there was no evidence of population-level clustering (K = 1), the pattern of isolation by distance (r = 0.17) was much weaker compared to marbled salamanders, and there was less variation in family-level structure (from 10 to 36 full-sibling families per site). We suspect that a combination of breeding site fidelity, effective population size, and generation interval is responsible for these marked differences. Our results suggest that marbled salamanders, compared to spotted salamanders, are more sensitive to fragmentation from various land-use activities and would be less likely to recolonize extirpated sites on an ecologically and conservation-relevant time frame. 相似文献
20.
Eran Elhaik 《PloS one》2012,7(11)
Studies of the apportionment of human genetic variation have long established that most human variation is within population groups and that the additional variation between population groups is small but greatest when comparing different continental populations. These studies often used Wright’s F
ST that apportions the standardized variance in allele frequencies within and between population groups. Because local adaptations increase population differentiation, high-F
ST may be found at closely linked loci under selection and used to identify genes undergoing directional or heterotic selection. We re-examined these processes using HapMap data. We analyzed 3 million SNPs on 602 samples from eight worldwide populations and a consensus subset of 1 million SNPs found in all populations. We identified four major features of the data: First, a hierarchically F
ST analysis showed that only a paucity (12%) of the total genetic variation is distributed between continental populations and even a lesser genetic variation (1%) is found between intra-continental populations. Second, the global F
ST distribution closely follows an exponential distribution. Third, although the overall F
ST distribution is similarly shaped (inverse J), F
ST distributions varies markedly by allele frequency when divided into non-overlapping groups by allele frequency range. Because the mean allele frequency is a crude indicator of allele age, these distributions mark the time-dependent change in genetic differentiation. Finally, the change in mean-F
ST of these groups is linear in allele frequency. These results suggest that investigating the extremes of the F
ST distribution for each allele frequency group is more efficient for detecting selection. Consequently, we demonstrate that such extreme SNPs are more clustered along the chromosomes than expected from linkage disequilibrium for each allele frequency group. These genomic regions are therefore likely candidates for natural selection. 相似文献