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1.
- Identifying spatial extent and temporal patterns of population genetic structure is important for understanding evolutionary relationships among local populations and for designing conservation programmes. However, little attention has been devoted to understand whether genetic structure is temporally stable or unstable, and how genetic characteristics may change over time. The goal of this study was to assess the temporal stability of the genetic structure of masu salmon (Oncorhynchus masou).
- To examine the temporal component of genetic variation in genetic structuring within a river system, we used 810 masu salmon collected from eight tributaries of the Atsuta River, Hokkaido, Japan, over three consecutive years (i.e. 2007–09). We assessed the temporal stability of the genetic structure in 15 microsatellite loci by comparing genetic diversity, effective population size and the relationships between genetic and geographical distances among samples collected from different tributaries and over time.
- Significant genetic differences were observed among most of the temporal samples collected from the same tributary, and analysis of molecular variance indicated that the temporal component explained about 10 times more of the genetic variation (1.98%) than did the spatial component (0.18%).
- Isolation by distance (IBD) was detected only in 2009. In addition, a significant correlation in population genetic structure was observed between samples collected in 2008 and those in 2009. In 2007, decomposed pairwise regression analysis identified one population as an outlier population and, following exclusion of the outlier sample, IBD was observed in 2007. This population is small and physically isolated by waterfall, in which the effective population size or effective number of breeders would be expected to be small.
- We found that fine‐scale genetic structure in masu salmon populations was temporally unstable, due perhaps to genetic drift in small isolated populations, temporal changes in environmental conditions (e.g. drought), and a combination of these factors. This study also highlights that the genetic structure among populations could easily be affected by temporal and/or sampling issues. Studies focused on temporal genetic structuring are likely to be important for conservation of species inhabiting unstable or isolated habitats such as freshwater fish.
2.
Siol M Bonnin I Olivieri I Prosperi JM Ronfort J 《Journal of evolutionary biology》2007,20(6):2349-2360
Despite its significance in evolutionary and conservation biology, few estimates of effective population size (N(e)) are available in plant species. Self-fertilization is expected to affect N(e), through both its effect on homozygosity and population dynamics. Here, we estimated N(e) using temporal variation in allele frequencies for two contrasted populations of the selfing annual Medicago truncatula: a large and continuous population and a subdivided population. Estimated N(e) values were around 5-10% of the population census size suggesting that other factors than selfing must contribute to variation in allele frequencies. Further comparisons between monolocus allelic variation and changes in the multilocus genotypic composition of the populations show that the local dynamics of inbred lines can play an important role in the fluctuations of allele frequencies. Finally, comparing N(e) estimates and levels of genetic variation suggest that H(e) is a poor estimator of the contemporaneous variance effective population size. 相似文献
3.
Andr Loureno Joo Gonalves Filipe Carvalho Ian J. Wang Guillermo Velo‐Antn 《Molecular ecology》2019,28(20):4573-4591
Evolutionary changes in reproductive mode may affect co‐evolving traits, such as dispersal, although this subject remains largely underexplored. The shift from aquatic oviparous or larviparous reproduction to terrestrial viviparous reproduction in some amphibians entails skipping the aquatic larval stage and, thus, greater independence from water. Accordingly, amphibians exhibiting terrestrial viviparous reproduction may potentially disperse across a wider variety of suboptimal habitats and increase population connectivity in fragmented landscapes compared to aquatic‐breeding species. We investigated this hypothesis in the fire salamander (Salamandra salamandra), which exhibits both aquatic‐ (larviparity) and terrestrial‐breeding (viviparity) strategies. We genotyped 426 larviparous and 360 viviparous adult salamanders for 13 microsatellite loci and sequenced a mitochondrial marker for 133 larviparous and 119 viviparous individuals to compare population connectivity and landscape resistance to gene flow within a landscape genetics framework. Contrary to our predictions, viviparous populations exhibited greater differentiation and reduced genetic connectivity compared to larviparous populations. Landscape genetic analyses indicate viviparity may be partially responsible for this pattern, as water courses comprised a significant barrier only in viviparous salamanders, probably due to their fully terrestrial life cycle. Agricultural areas and, to a lesser extent, topography also decreased genetic connectivity in both larviparous and viviparous populations. This study is one of very few to explicitly demonstrate the evolution of a derived reproductive mode affects patterns of genetic connectivity. Our findings open avenues for future research to better understand the eco‐evolutionary implications underlying the emergence of terrestrial reproduction in amphibians. 相似文献
4.
Judit Vörös Sylvain Ursenbacher István Kiss Dušan Jelić Silke Schweiger Krisztián Szabó 《Journal of Zoological Systematics and Evolutionary Research》2017,55(2):138-149
The traditional southern Pleistocene refugia hypothesis in Europe has lately been challenged for several animal and plant species. The Carpathian Basin, especially at the marginal regions, is one of the recently recognized biodiversity hotspots in Europe. Marginal populations are prone to have lower genetic diversity and higher genetic differentiation than central populations. Here, we examined one mitochondrial DNA fragment (D‐loop) and nine nuclear (microsatellite) loci to describe the genetic diversity and phylogeographical pattern of fire salamander (Salamandra salamandra) populations in the Carpathian Basin with focusing on the southern margins of the Western Carpathians, where isolated populations of this species are present. Analyses of microsatellites indicated reduced genetic diversity for most of the isolated populations. Based on the mitochondrial DNA, only two haplotypes were found, whereas the analyses with the nuclear markers revealed a more recent genetic split between Western (Alpine) and Eastern (Carpathian) populations, and separated the Apuseni Mountains population (part of the Western Carpathians). Using approximate Bayesian computation analyses, we identified the most probable colonization scenario for the isolated North Hungarian Carpathian Basin populations. The split between isolated salamander populations from the central populations in the Carpathian Mountains dates back to the beginning of the Late Pleistocene, while the split between most of the Hungarian populations can be associated with the Last Glacial Maximum. We found evidence for long‐time isolation between the marginal Carpathian Basin and central populations. Our results also show that S. salamandra survived glacial periods in the temperate forests of north‐east Pannonia (North Hungarian Mountains), confirming that the Carpathian Basin served as important northerly refugia during the Pleistocene climatic oscillations. 相似文献
5.
Supen Wang Wei Zhu Xu Gao Xianping Li Shaofei Yan Xuan Liu Ji Yang Zengxiang Gao Yiming Li 《Molecular ecology》2014,23(3):637-648
Understanding the factors that contribute to loss of genetic diversity in fragmented populations is crucial for conservation measurements. Land‐bridge archipelagoes offer ideal model systems for identifying the long‐term effects of these factors on genetic variations in wild populations. In this study, we used nine microsatellite markers to quantify genetic diversity and differentiation of 810 pond frogs (Pelophylax nigromaculatus) from 24 islands of the Zhoushan Archipelago and three sites on nearby mainland China and estimated the effects of the island area, population size, time since island isolation, distance to the mainland and distance to the nearest larger island on reduced genetic diversity of insular populations. The mainland populations displayed higher genetic diversity than insular populations. Genetic differentiations and no obvious gene flow were detected among the frog populations on the islands. Hierarchical partitioning analysis showed that only time since island isolation (square‐root‐transformed) and population size (log‐transformed) significantly contributed to insular genetic diversity. These results suggest that decreased genetic diversity and genetic differentiations among insular populations may have been caused by random genetic drift following isolation by rising sea levels during the Holocene. The results provide strong evidence for a relationship between retained genetic diversity and population size and time since island isolation for pond frogs on the islands, consistent with the prediction of the neutral theory for finite populations. Our study highlights the importance of the size and estimated isolation time of populations in understanding the mechanisms of genetic diversity loss and differentiation in fragmented wild populations. 相似文献
6.
Joseph D. Holbrook Randy W. DeYoung Michael E. Tewes John H. Young 《Evolutionary Applications》2012,5(6):619-628
Elusive carnivores present a challenge to managers because traditional survey methods are not suitable. We applied a genetic approach using museum specimens to examine how historical and recent conditions influenced the demographic history of Puma concolor in western and southern Texas, USA. We used 10 microsatellite loci and indexed population trends by estimating historical and recent genetic diversity, genetic differentiation and effective population size. Mountain lions in southern Texas exhibited a 9% decline in genetic diversity, whereas diversity remained stable in western Texas. Genetic differentiation between western and southern Texas was minimal historically (FST = 0.04, P < 0.01), but increased 2–2.5 times in our recent sample. An index of genetic drift for southern Texas was seven to eight times that of western Texas, presumably contributing to the current differentiation between western and southern Texas. Furthermore, southern Texas exhibited a >50% temporal decline in effective population size, whereas western Texas showed no change. Our results illustrate that population declines and genetic drift have occurred in southern Texas, likely because of contemporary habitat loss and predator control. Population monitoring may be needed to ensure the persistence of mountain lions in the southern Texas region. This study highlights the utility of sampling museum collections to examine demographic histories and inform wildlife management. 相似文献
7.
The effective population size Ne is a key parameter in population genetics and evolutionary biology, as it quantifies the expected distribution of changes in allele frequency due to genetic drift. Several methods of estimating Ne have been described, the most direct of which uses allele frequencies measured at two or more time points. A new likelihood-based estimator for contemporary effective population size using temporal data is developed in this article. The existing likelihood methods are computationally intensive and unable to handle the case when the underlying Ne is large. This article tries to work around this problem by using a hidden Markov algorithm and applying continuous approximations to allele frequencies and transition probabilities. Extensive simulations are run to evaluate the performance of the proposed estimator , and the results show that it is more accurate and has lower variance than previous methods. The new estimator also reduces the computational time by at least 1000-fold and relaxes the upper bound of Ne to several million, hence allowing the estimation of larger Ne. Finally, we demonstrate how this algorithm can cope with nonconstant Ne scenarios and be used as a likelihood-ratio test to test for the equality of Ne throughout the sampling horizon. An R package “NB” is now available for download to implement the method described in this article. 相似文献
8.
Irene Novo Noelia Pérez-Pereira Enrique Santiago Humberto Quesada Armando Caballero 《Molecular ecology resources》2023,23(7):1632-1640
The availability of a large number of high-density markers (SNPs) allows the estimation of historical effective population size (Ne) from linkage disequilibrium between loci. A recent refinement of methods to estimate historical Ne from the recent past has been shown to be rather accurate with simulation data. The method has also been applied to real data for numerous species. However, the simulation data cannot encompass all the complexities of real genomes, and the performance of any estimation method with real data is always uncertain, as the true demography of the populations is not known. Here, we carried out an experimental design with Drosophila melanogaster to test the method with real data following a known demographic history. We used a population maintained in the laboratory with a constant census size of about 2800 individuals and subjected the population to a drastic decline to a size of 100 individuals. After a few generations, the population was expanded back to the previous size and after a few further generations again expanded to twice the initial size. Estimates of historical Ne were obtained with the software GONE both for autosomal and X chromosomes from samples of 17 individuals sequenced for the whole genome. Estimates of the historical effective size were able to infer the patterns of changes that occurred in the populations showing generally good performance of the method. We discuss the limitations of the method and the application of the software carried out so far. 相似文献
9.
André Lourenço Fernando Sequeira David Buckley Guillermo Velo‐Antón 《Journal of Biogeography》2018,45(5):1054-1066
10.
植物亲缘地理学的研究现状与发展趋势 总被引:2,自引:0,他引:2
新生代以来剧烈的地质和气候变化,特别是第四纪冰期和间冰期的反复交错对温带植物类群的地理分布格局、种群结构和物种分化造成了深刻影响。近20年来,随着分子标记技术的发展和分析方法的成熟,植物亲缘地理学利用基因谱系关系和在种群中的时空分布来追溯种群的进化历史,在探讨植物类群对地质气候变迁的响应以及种群分化的历史成因等方面开展了大量工作,取得了一些重要进展。在取得这些成绩的同时,作者也注意到了被研究者所忽略的一些问题。试图对这些问题进行初步的总结,着重于分析方法和几个常用软件的使用,并对今后的发展趋势进行了展望。 相似文献
11.
Population viability has often been assessed by census of reproducing adults. Recently this method has been called into question and estimation of the effective population size (Ne) proposed as a complementary method to determine population health. We examined genetic diversity in five populations of chinook salmon (Oncorhynchus tshawytscha) from the upper Fraser River watershed (British Columbia, Canada) at 11 microsatellite loci over 20 years using DNA extracted from archived scale samples. We tested for changes in genetic diversity, calculated the ratio of the number of alleles to the range in allele size to give the statistic M, calculated Ne from the temporal change in allele frequency, used the maximum likelihood method to calculate effective population size (NeM), calculated the harmonic mean of population size, and compared these statistics to annual census estimates. Over the last two decades population size has increased in all five populations of chinook examined; however, Ne calculated for each population was low (81-691) and decreasing over the time interval measured. Values of NeM were low, but substantially higher than Ne calculated using the temporal method. The calculated values for M were generally low (M < 0.70), indicating recent population reductions for all five populations. Large-scale historic barriers to migration and development activities do not appear to account for the low values of Ne; however, available spawning area is positively correlated with Ne. Both Ne and M estimates indicate that these populations are potentially susceptible to inbreeding effects and may lack the ability to respond adaptively to stochastic events. Our findings question the practice of relying exclusively on census estimates for interpreting population health and show the importance of determining genetic diversity within populations. 相似文献
12.
Summary The allozyme variability of 38 genetic loci coding for blood proteins was compared in up to 95 Black Grouse originating from Bavaria, the Netherlands and two sites in Sweden, bred to restock the Central European lowland populations. Polymorphisms are described forAda*,Pgd*, andPgm-1*, yielding an overall fraction of polymorphic loci of P=0.079, and an observed heterozygosity of Ho=0.015 (He=0.018). The genotype distributions at theAda* locus differed significantly between regional stocks, but unbiased standard distances measured D=0.0060 at most. Considering the inferred importance of genetic drift for Black Grouse microevolution, these slight genetic distances do not provide a basis for judging the validity of a suggested subspecies from the Netherlands. The weight differences of the eggs laid by grouse from different regional stocks reached statistical significance. A heterosis effect is inferred from the heavier eggs produced by F1 crosses between parents originating from disparate geographic origins.
Genetische Variabilität beim Birkhuhn (Tetrao tetrix), ein Hühnervogel mit Arenabalz
Zusammenfassung Die elektrophoretische Variabilität (38 Proteinloci) von Birkhühnern (Tetrao tetrix) wurde an Populationen aus Schweden, Bayern und den Niederlanden untersucht (n=95). Dabei handelt es sich um einige Gründertiere (teilweise Wildfänge) definierter geographischer Herkünfte für die Auswilderungszucht des Instituts für Wildtierforschung (Hannover) oder um deren Nachzuchten. Variabilität der EnzymeAda*,Pgd* undPgm-1* erbrachten einen Polymorphismus von P=0,079 und eine Heterozygotie von Ho=0.015 (He=0.018). Die Genotypenverteilung desAda*-Locus differenzierte regionale Populationen, jedoch betrugen die stichprobenkorrigierten genetischen Distanzen zwischen den Herkünften lediglich D=0.0060 oder waren geringer. Die geringe Mischerbigkeit wird hypothetisch mit relativ hoher genetischer Drift in Zusammenhang gebracht, weshalb sich Allozympolymorphismen beim Birkhuhn auch nur eingeschränkt zur Analyse von (unterartlichen) Populationsunterschieden eignen könnten, zumindest solange die Stichproben nicht erheblich ausgeweitet werden. Die Eigewichte von Hennen verschiedener regionaler Herkünfte unterscheiden sich signifikant, die Eier von Mischlingen zwischen Linien sind schwerer (Heterosiseffekt?). Die geringe Mischerbigkeit der untersuchten Birkhühner mag mit Faktoren der arteigenen Lebensweise (Arenabalz mit Polygynie, Varianz der Fruchtbarkeit unterschiedlicher Familien aufgrund hoher Kükensterblichkeit, Bestandesfluktuationen) erklärt werden. Die in den kleinen, isolierten Reliktbestände in Niedersachsen verbleibende genetische Variabilität dürfte sehr rasch verloren gehen, sofern die verbleibenden Habitate nicht durch Trittsteine verbunden werden, deren Abstände dem Ausbreitungsradius des Birkwildes Rechnung tragen.相似文献
13.
Helle Tessand Baalsrud Bernt‐Erik Sæther Ingerid Julie Hagen Ane Marlene Myhre Thor Harald Ringsby Henrik Pärn Henrik Jensen 《Molecular ecology》2014,23(11):2653-2668
Effective population size (Ne) is a key parameter to understand evolutionary processes and the viability of endangered populations as it determines the rate of genetic drift and inbreeding. Low Ne can lead to inbreeding depression and reduced population adaptability. In this study, we estimated contemporary Ne using genetic estimators (LDNE, ONeSAMP, MLNE and CoNe) as well as a demographic estimator in a natural insular house sparrow metapopulation. We investigated whether population characteristics (population size, sex ratio, immigration rate, variance in population size and population growth rate) explained variation within and among populations in the ratio of effective to census population size (Ne/Nc). In general, Ne/Nc ratios increased with immigration rates. Genetic Ne was much larger than demographic Ne, probably due to a greater effect of immigration on genetic than demographic processes in local populations. Moreover, although estimates of genetic Ne seemed to track Nc quite well, the genetic Ne‐estimates were often larger than Nc within populations. Estimates of genetic Ne for the metapopulation were however within the expected range (<Nc). Our results suggest that in fragmented populations, even low levels of gene flow may have important consequences for the interpretation of genetic estimates of Ne. Consequently, further studies are needed to understand how Ne estimated in local populations or the total metapopulation relates to actual rates of genetic drift and inbreeding. 相似文献
14.
We present here a spatial and temporal population genetic survey of a common freshwater snail, also a predominantly selfing species, Lymnaea truncatula. The rate of genetic diversity loss was quantified by estimating the effective size (Ne) of the snail populations, using two different methods. A temporal survey allowed estimation of a variance effective size of the populations, and a spatial survey allowed the estimation of an inbreeding effective size, from two-locus identity disequilibria estimates. Both methods were consistent and provided low Ne values. Drift due to (i) high amounts of selfing and (ii) fluctuations in population sizes because of temporary habitats, and also selection coupled to genome-wide linkage disequilibria, could explain such reductions in Ne. The loss of genetic diversity appears to be counterbalanced only very partially by low apparent rates of gene flow. 相似文献
15.
NICOLAS GOUIN CATHERINE SOUTY‐GROSSET JÉSSICA BÓRQUEZ ANGÉLINE BERTIN FRÉDÉRIC GRANDJEAN 《Freshwater Biology》2011,56(10):2105-2118
1. Habitat fragmentation of stream ecosystems often results in decreased connectivity between populations and lower population sizes. Hence, understanding how habitat fragmentation affects genetic erosion is important for the preservation of freshwater biodiversity, in particular, as small populations suffer from loss of genetic diversity through genetic drift and loss of fitness because of inbreeding, increasing the risk of extinction. 2. Here, we assess the impact of demographic factors on population differentiation in the endangered freshwater crayfish Austropotamobius pallipes by analysing population genetic structure, estimating effective population sizes and comparing levels of polymorphism at five microsatellite loci with density estimates of 10 populations within a small French catchment that has become progressively confined to headwaters over the last six decades. 3. Levels of expected heterozygosity and allelic richness per population were relatively low (0.214–0.396 and 1.6–2.6, respectively). We found strong genetic differentiation between these geographically close populations (FST = 0.283), with weak statistical evidence for a pattern of isolation by distance. Estimates of effective population size were low (<150) in most populations, but potentially reached several thousands in three populations. 4. Population density and allelic richness were strongly positively correlated. A robust relationship between population density and heterozygosity values was also noted, but only after discarding two populations for which significant genetic signatures of a recent bottleneck were found; these two populations displayed high expected heterozygosity compared with a very low density. Populations with the highest densities of individuals had the highest effective population size estimates and vice versa. 5. Our results clearly show the importance of demographic factors and genetic drift on A. pallipes populations. Furthermore, analysis of genetic and population density data is a pragmatic and efficient approach to corroborate inferences from genetic data and can be particularly useful in the identification of populations experiencing a bottleneck and therefore in conservation genetics studies aiming at identifying priority populations for conservation. 相似文献
16.
Selection and mating methods for controlling inbreeding in selection programmes are based on relationships obtained from pedigrees. The efficiency of these methods has always been tested by studies using genetic models of independent loci. However, under linkage the rate of inbreeding obtained from pedigrees can be different from the probability of identity by descent of genes. We simulated a quantitative trait under artificial selection controlled by a large number of genes spread on genome regions of different sizes. A method to control inbreeding based on minimising the average coancestry of selected individuals with a restriction in the loss of selection response, and a mating procedure to control inbreeding were applied. These methods, that use coancestry relationships, were not effective in controlling inbreeding when the genome sizes were smaller than five morgans or so. However, for larger genome sizes the methods were sufficiently efficient. For very tight linkage, methods that utilise molecular information from markers should be used. We finally discuss the effects of the selection of individual major genes on the neutral variability of adjacent genome regions. 相似文献
17.
Ben Qin 《Journal of evolutionary biology》2023,36(2):347-354
Unequal breeding sex ratio can significantly reduce effective population size, allowing a rare neutral allele to jump to a high frequency through genetic drift. However, this one-way alteration to allele frequency appears inconsistent with the concept that drift is non-directional. Based on binomial sampling distribution, this study developed a method to directly and exhaustively measure drift by calculating the mean deviation of change in allele frequency, then applied it to cases of unequal breeding sex ratio. The result shows that, under those cases, (1) the mean deviation can always be divided into two halves that are equal in size but opposite in direction; (2) each half consists of one or several categories represented by various allele proportions in the rare sex; (3) this proportion is another factor that determines the outcome of drift, in addition to effective population size and allele frequency; (4) drift is non-directional on a global scale, but whether an allele will drift up or down can be predicted based on the above factors. This method enables us to dissect every component of the expected change in allele frequency caused by drift and to find out the combined effect of population size, allele frequency and allele proportion in the rarer sex under neutrality but unequal breeding sex ratio. 相似文献
18.
W. Chris Funk Robert E. Lovich Paul A. Hohenlohe Courtney A. Hofman Scott A. Morrison T. Scott Sillett Cameron K. Ghalambor Jesus E. Maldonado Torben C. Rick Mitch D. Day Nicholas R. Polato Sarah W. Fitzpatrick Timothy J. Coonan Kevin R. Crooks Adam Dillon David K. Garcelon Julie L. King Christina L. Boser Nicholas Gould William F. Andelt 《Molecular ecology》2016,25(10):2176-2194
The evolutionary mechanisms generating the tremendous biodiversity of islands have long fascinated evolutionary biologists. Genetic drift and divergent selection are predicted to be strong on islands and both could drive population divergence and speciation. Alternatively, strong genetic drift may preclude adaptation. We conducted a genomic analysis to test the roles of genetic drift and divergent selection in causing genetic differentiation among populations of the island fox (Urocyon littoralis). This species consists of six subspecies, each of which occupies a different California Channel Island. Analysis of 5293 SNP loci generated using Restriction‐site Associated DNA (RAD) sequencing found support for genetic drift as the dominant evolutionary mechanism driving population divergence among island fox populations. In particular, populations had exceptionally low genetic variation, small Ne (range = 2.1–89.7; median = 19.4), and significant genetic signatures of bottlenecks. Moreover, islands with the lowest genetic variation (and, by inference, the strongest historical genetic drift) were most genetically differentiated from mainland grey foxes, and vice versa, indicating genetic drift drives genome‐wide divergence. Nonetheless, outlier tests identified 3.6–6.6% of loci as high FST outliers, suggesting that despite strong genetic drift, divergent selection contributes to population divergence. Patterns of similarity among populations based on high FST outliers mirrored patterns based on morphology, providing additional evidence that outliers reflect adaptive divergence. Extremely low genetic variation and small Ne in some island fox populations, particularly on San Nicolas Island, suggest that they may be vulnerable to fixation of deleterious alleles, decreased fitness and reduced adaptive potential. 相似文献
19.
Genetic differentiation between three populations of the pied flycatcher Ficedula hypoleuca (Norway, Czech Republic and Spain, respectively) was investigated at microsatellite loci and mitochondrial DNA (mtDNA) sequences and compared with the pattern of differentiation of male plumage colour. The Czech population lives sympatrically with the closely related collared flycatcher (F. albicollis) whereas the other two are allopatric. Allopatric populations are on average more conspicuously coloured than sympatric ones, a pattern that has been explained by sexual selection for conspicuous colour in allopatry and a character displacement on breeding plumage colour in sympatry that reduces the rate of hybridization with the collared flycatcher. The Czech population was genetically indistinguishable from the Norwegian population at microsatellite loci and mtDNA sequences. Recent isolation and/or gene flow may explain the lack of genetic differentiation. Accordingly, different selection on plumage colour in the two populations is either sufficiently strong so that gene flow has little impact on the pattern of colour variation, or differentiation of plumage colour occurred so recently that the (presumably) neutral, fast evolving markers employed here are unable to reflect the differentiation. Genetically, the Spanish population was significantly differentiated from the other populations, but the divergence was much more pronounced at mtDNA compared to microsatellites. This may reflect increased rate of differentiation by genetic drift at the mitochondrial, compared with the nuclear genome, caused by the smaller effective population size of the former genome. In accordance with this interpretation, a genetic pattern consistent with effects of small population size in the Spanish population (genetic drift and inbreeding) were also apparent at the microsatellites, namely reduced allelic diversity and heterozygous deficiency. 相似文献
20.
Alexander Kopatz Hans Geir Eiken Julia Schregel Jouni Aspi Ilpo Kojola Snorre B. Hagen 《Ecology and evolution》2017,7(24):10721-10732
The number of effective breeders (Nb) and effective population size (Ne) are population parameters reflective of evolutionary potential, susceptibility to stochasticity, and viability. We have estimated these parameters using the linkage disequilibrium‐based approach with LDNE through the latest phase of population recovery of the brown bears (Ursus arctos) in Finland (1993–2010; N = 621). This phase of the recovery was recently documented to be associated with major changes in genetic composition. In particular, differentiation between the northern and the southern genetic cluster declined rapidly within 1.5 generations. Based on this, we have studied effects of the changing genetic structure on Nb and Ne, by comparing estimates for whole Finland with the estimates for the two genetic clusters. We expected a potentially strong relationship between estimate sizes and genetic differentiation, which should disappear as the population recovers and clusters merge. Consistent with this, our estimates for whole Finland were lower than the sum of the estimates of the two genetic clusters and both approaches produced similar estimates in the end. Notably, we also found that admixed genotypes strongly increased the estimates. In all analyses, our estimates for Ne were larger than Nb and likely reflective for brown bears of the larger region of Finland and northwestern Russia. Conclusively, we find that neglecting genetic substructure may lead to a massive underestimation of Nb and Ne. Our results also suggest the need for further empirical analysis focusing on individuals with admixed genotypes and their potential high influence on Nb and Ne. 相似文献