New data on coat color gene frequencies in cats: 1. The Armavir population

The population of domestic cats from the city of Armavir has been examined. A high frequency of gene O was revealed in the population. Differences among three subpopulations estimated using two genetic distances showed heterogeneity of the Armavir cat population. The extreme samples showed highly significant differences (P < 0.01; χ _[6] ² = 24.67), likely explained by the structural features of the synantropous population and human-driven frequency-dependent selection operating in it. The feline population of Armavir underwent significant changes during the past two decades. The d _ij coefficient in it was 0.093; D _p = 0.05. The frequencies of genes Orange and Long-hair have increased in the general population. The frequency of gene dilution has decreased. These changes may have occurred because of genetic exchange with purebred domestic cats that have become more popular as pets in the recent years.     

Genetic identification of wild and domestic cats (Felis silvestris) and their hybrids using Bayesian clustering methods

Crossbreeding with free-ranging domestic cats is supposed to threaten the genetic integrity of wildcat populations in Europe, although the diagnostic markers to identify "pure" or "admixed" wildcats have never been clearly defined. Here we use mitochondrial (mt) DNA sequences and allelic variation at 12 microsatellite loci to genotype 128 wild and domestic cats sampled in Italy which were preclassified into three separate groups: European wildcats (Felis silvestris silvestris), Sardinian wildcats (Felis silvestris libyca), and domestic cats (Felis silvestris catus), according to their coat color patterns, collection localities, and other phenotypical traits, independently of any genetic information. For comparison, we included some captive-reared hybrids of European wild and domestic cats. Genetic variability was significantly partitioned among the three groups (mtDNA estimate of F(ST) = 0.36; microsatellite estimate of R(ST) = 0.30; P < 0.001), suggesting that morphological diversity reflects the existence of distinct gene pools. Multivariate ordination of individual genotypes and clustering of interindividual genetic distances also showed evidence of distinct cat groups, partially congruent with the morphological classification. Cluster analysis, however, did not enable hybrid cats to be identified from genetic information alone, nor were all individuals assigned to their populations. In contrast, a Bayesian admixture analysis simultaneously assigned the European wildcats, the Sardinian wildcats, and the domestic cats to different clusters, independent of any prior information, and pointed out the admixed gene composition of the hybrids, which were assigned to more than one cluster. Only one putative Sardinian wildcat was assigned to the domestic cat cluster, and one presumed European wildcat showed mixed (hybrid) ancestry in the domestic cat gene pool. Mitochondrial DNA sequences indicated that three additional presumed European wildcats might have hybrid ancestry. These four cats were sampled from the same area in the northernmost edge of the European wildcat distribution in the Italian Apennines. Admixture analyses suggest that wild and domestic cats in Italy are distinct, reproductively isolated gene pools and that introgression of domestic alleles into the wild-living population is very limited and geographically localized.     

Genetic diversity and integrity of German wildcat (Felis silvestris) populations as revealed by microsatellites,allozymes, and mitochondrial DNA sequences

As a consequence of persecution and habitat fragmentation, wildcats (Felis silvestris silvestris) in Western Europe have experienced a severe reduction in population numbers and sizes. The remaining wildcat populations are considered to be endangered by losses of genetic variability and by hybridisation with free-ranging domestic cats. To investigate genetic diversity within and among wild and domestic cat populations in Germany and to estimate the extent of gene flow between both forms, we analysed a total of 266 individuals. PCR-amplification and sequencing of 322 base pairs of a highly variable part of the mitochondrial control region (HV1) of 244 specimens resulted in 41 haplotypes with 31 polymorphic sites. Additionally, eight microsatellite loci were examined for those 244 cats. Moreover, a total of 46 wildcats and 22 domestic cats could be genotyped for 13 polymorphic out of 31 enzyme loci. Genetic variability in both groups was generally high. Variability in domestic cat populations was higher than in wildcat populations. Almost no differentiation between domestic cat populations could be found (F_ST for microsatellites=3%). In contrast, wildcat populations differed significantly from one another (F_ST for microsatellites=9.55%) Within the smaller wildcat populations, a reduction of genetic diversity was detectable with regard to the nuclear DNA. Wildcat and domestic cat mitochondrial haplotypes were separated, suggesting a very low level of maternal gene flow between both forms. In microsatellites and to a somewhat lesser extent in allozymes, wildcats and domestic cats showed distinct differentiation, suggesting an only low extent of past hybridisation in certain populations. The microsatellite data set indicated a significantly reduced effective population size (bottleneck) in the recent past for one German wildcat population.     

Genetic distinction of wildcat (Felis silvestris) populations in Europe,and hybridization with domestic cats in Hungary

The genetic integrity and evolutionary persistence of declining wildcat populations are threatened by crossbreeding with widespread free-living domestic cats. Here we use allelic variation at 12 microsatellite loci to describe genetic variation in 336 cats sampled from nine European countries. Cats were identified as European wildcats (Felis silvestris silvestris), Sardinian wildcats (F. s. libyca) and domestic cats (F. s. catus), according to phenotypic traits, geographical locations and independently of any genetic information. Genetic variability was significantly partitioned among taxonomic groups (FST = 0.11; RST = 0.41; P < 0.001) and sampling locations (FST = 0.07; RST = 0.06; P < 0.001), suggesting that wild and domestic cats are subdivided into distinct gene pools in Europe. Multivariate and Bayesian clustering of individual genotypes also showed evidence of distinct cat groups, congruent with current taxonomy, and suggesting geographical population structuring. Admixture analyses identified cryptic hybrids among wildcats in Portugal, Italy and Bulgaria, and evidenced instances of extensive hybridization between wild and domestic cats sampled in Hungary. Cats in Hungary include a composite assemblage of variable phenotypes and genotypes, which, as previously documented in Scotland, might originate from long lasting hybridization and introgression. A number of historical, demographic and ecological conditions can lead to extensive crossbreeding between wild and domestic cats, thus threatening the genetic integrity of wildcat populations in Europe.     

Strong spatial segregation between wildcats and domestic cats may explain low hybridization rates on the Iberian Peninsula

The European wildcat (Felis silvestris silvestris) is an endangered felid impacted by genetic introgression with the domestic cat (Felis silvestris catus). The problem of hybridization has had different effects in different areas. In non-Mediterranean regions pure forms of wildcats became almost extinct, while in Mediterranean regions genetic introgression is a rare phenomenon. The study of the potential factors that prevent the gene flow in areas of lower hybridization may be key to wildcat conservation. We studied the population size and spatial segregation of wildcats and domestic cats in a typical Mediterranean area of ancient sympatry, where no evidence of hybridization had been detected by genetic studies. Camera trapping of wild-living cats and walking surveys of stray cats in villages were used for capture–recapture estimations of abundance and spatial segregation. Results showed (i) a low density of wildcats and no apparent presence of putative hybrids; (ii) a very low abundance of feral cats in spite of the widespread and large population sources of domestic cats inhabiting villages; (iii) strong spatial segregation between wildcats and domestic/feral cats; and (iv) no relationship between the size of the potential population sources and the abundance of feral cats. Hence, domestic cats were limited in their ability to become integrated into the local habitat of wildcats. Ecological barriers (habitat preferences, food limitations, intra-specific and intra-guild competition, predation) may explain the severe divergences of hybridization impact observed at a biogeographic level. This has a direct effect on key conservation strategies for wildcats (i.e., control of domestic cats).     

Genetic diversity in domestic cats Felis catus of the Tsushima Islands, based on mitochondrial DNA cytochrome b and control region nucleotide sequences

Nucleotide sequences of mitochondrial DNA (mtDNA) of 50 domestic cats (Felis catus) obtained from the Tsushima Islands were determined and the genetic diversity was analyzed. In the cats, six haplotypes of the complete cytochrome b sequences (1,140 base-pairs, bp) and ten haplotypes of the partial control region sequences (350 bp) were identified. Haplotypes obtained from both genes showed existence of at least 11 maternal lineages of domestic cats in Tsushima. Mean values of polymorphic site numbers and sequences differences in the control region were 2.4 times and 1.8 times higher than those in the cytochrome b gene, respectively. Our results support the idea that the evolutionary rate of the control region was faster than that of the cytochrome b as reported in other mammals. Molecular phylogenetic trees showed the similar clustering of haplotypes for both genes. Meanwhile, no individual variations within the Tsushima leopard cat (Felis bengalensis euptilura), which is native to Tsushima, were observed, possibly as a result of genetic drift in the small ancestral population by geographical isolation. In contrast, the diversity of the domestic cat population was higher than that of the leopard cats, because the genetic variability of the former's founders, which were repeatedly brought to Tsushima in the past, still remains. In addition, no sequences of the leopard cat mtDNA were detected in any domestic cats. However, because the possibility that the domestic cat would crossbreed with the leopard cat cannot be denied, genetic monitoring of two species is necessary to biological conservation in Tsushima.     

The Genetic Integrity of the Ex Situ Population of the European Wildcat (Felis silvestris silvestris) Is Seriously Threatened by Introgression from Domestic Cats (Felis silvestris catus)

Studies on the genetic diversity and relatedness of zoo populations are crucial for implementing successful breeding programmes. The European wildcat, Felis s. silvestris, is subject to intensive conservation measures, including captive breeding and reintroduction. We here present the first systematic genetic analysis of the captive population of Felis s. silvestris in comparison with a natural wild population. We used microsatellites and mtDNA sequencing to assess genetic diversity, structure and integrity of the ex situ population. Our results show that the ex situ population of the European wildcat is highly structured and that it has a higher genetic diversity than the studied wild population. Some genetic clusters matched the breeding lines of certain zoos or groups of zoos that often exchanged individuals. Two mitochondrial haplotype groups were detected in the in situ populations, one of which was closely related to the most common haplotype found in domestic cats, suggesting past introgression in the wild. Although native haplotypes were also found in the captive population, the majority (68%) of captive individuals shared a common mtDNA haplotype with the domestic cat (Felis s. catus). Only six captive individuals (7.7%) were assigned as wildcats in the STRUCTURE analysis (at K = 2), two of which had domestic cat mtDNA haplotypes and only two captive individuals were assigned as purebred wildcats by NewHybrids. These results suggest that the high genetic diversity of the captive population has been caused by admixture with domestic cats. Therefore, the captive population cannot be recommended for further breeding and reintroduction.     

Genetic diversity and introgression in the Scottish wildcat

This paper describes a genetic analysis of wild-living cats in Scotland. Samples from 230 wild-living Scottish cats (including 13 museum skins) and 74 house cats from England and Scotland were surveyed for nine microsatellite loci. Pelage characteristics of the wild-living cats were recorded, and the cats were then grouped into five separate categories depending on the degree to which they conformed to the characteristics attributed to Felis silvestris Schreber, 1775. Allele frequency differences between the morphological groups are greater than those among the three house cat samples. Analysis of genetic distances suggests that more of the differences between individuals can be explained by pelage than geographical proximity, and that pelage and geographical location are not confounded. Ordination of the genetic distances suggests two main groups of wild-living cats, with intermediates, and one group is genetically very similar to the house cats, while the other group contains all cats taxonomically identified as wildcat based on morphology. A genetic mixture analysis gives similar results to the ordination, but also suggests that the genotypes of a substantial number of cats in the wildcat group are drawn from a gene pool with genotypes in approximately equilibrium proportions. We argue that this is evidence that these cats do not have very recent domestic ancestry. However, from the morphological data it is highly likely that this gene pool also contains a contribution from earlier introgression of domestic cat genes.     

Molecular analysis of hybridisation between wild and domestic cats (Felis silvestris) in Portugal: implications for conservation

The endangered European wildcat (Felis silvestris silvestris) is represented, today, by fragmented and declining populations whose genetic integrity is considered to be seriously threatened by crossbreeding with widespread free-ranging domestic cats. Extensive and recent hybridisation has been described in Hungary and Scotland, in contrast with rare introgression of domestic alleles in Italy and Germany. In Portugal, the wildcat is now listed as VULNERABLE in the Red Book of Portuguese Vertebrates. Nevertheless, genetic diversity of populations and the eventual interbreeding with domestic cats remain poorly studied. We surveyed genetic variation at 12 autosomal microsatellites for 34 wild and 64 domestic cats collected across Portugal. Wild and domestic cats were significantly differentiated both at allele frequencies and sizes (F _ST=0.11, R _ST = 0.18, P < 0.001). Population structure and admixture analyses performed using Bayesian approaches also showed evidence of two discrete groups clustering wild and domestic populations. Results did not show significant genetic divergence among Northern, Central and Southern wildcats. Six morphologically identified wildcats were significantly assigned to the domestic cluster, revealing some discrepancy between phenotypic and genetic identifications. We detected four hybrids (approximately 14%) using a consensus analysis of different Bayesian model-based software. These hybrids were identified throughout all sampled areas, suggesting that hybridisation is of major concern for the appropriate implementation of wildcat conservation strategies in Portugal.     

Large-scale genetic census of an elusive carnivore,the European wildcat (<Emphasis Type="Italic">Felis s. silvestris</Emphasis>)

The European wildcat, Felis silvestris silvestris, serves as a prominent target species for the reconnection of central European forest habitats. Monitoring of this species, however, appears difficult due to its elusive behaviour and the ease of confusion with domestic cats. Recently, evidence for multiple wildcat occurrences outside its known distribution has accumulated in several areas across Central Europe, questioning the validity of available distribution data for this species. Our aim was to assess the fine-scale distribution and genetic status of the wildcat in its central European distribution range. We compiled and analysed genetic samples from roadkills and hundreds of recent hair-trapping surveys and applied phylogenetic and genetic clustering methods to discriminate wild and domestic cats and identify population subdivision. 2220 individuals were confirmed as either wildcat (n = 1792) or domestic cat (n = 342), and the remaining 86 (3.9 %) were identified as hybrids between the two. Remarkably, genetic distinction of domestic cats, wildcats and their hybrids was only possible when taking into account the presence of two highly distinct genetic lineages of wildcats, with a suture zone in central Germany. 44 % of the individual wildcats where sampled outside the previously published distribution. Our analyses confirm a relatively continuous spatial presence of wildcats across large parts of the study area in contrast to previous analyses indicating a highly fragmented distribution. Our results suggest that wildcat conservation and management should take advantage of the higher than previously assumed dispersal potential of wildcats, which may use wildlife corridors very efficiently.     

Mitochondrial haplotypes of European wild boars with 2n = 36 are closely related to those of European domestic pigs with 2n = 38

Wild boars from Western Europe have a 2n = 36 karyotype, in contrast to a karyotype of 2n = 38 in wild boars from Central Europe and Asia and in all domestic pigs. The phylogenetic status of this wild boar population is unclear, and it is not known if it has contributed to pig domestication. We have now sequenced the mtDNA control region from 30 European wild boars (22 with a confirmed 2n = 36 karyotype) and six Asian wild boars (two Hainan and four Dongbei wild boars) to address this question. The results revealed a close genetic relationship between mtDNA haplotypes from wild boars with 2n = 36 to those from domestic pigs with 2n = 38. Thus, we cannot exclude the possibility that wild boars with 2n = 36 may have contributed to pig domestication despite the karyotype difference. One of the European wild boars carried an Asian mtDNA haplotype, and this most likely reflects gene flow from domestic pigs to European wild boars. However, this gene flow does not appear to be extensive because the frequency of Asian haplotypes detected among European wild boars (c. 3%) were 10-fold lower than among European domestic pigs (c. 30%). Previous studies of mtDNA haplotypes have indicated that pig populations in Europe and Asia have experienced a population expansion, but it is not clear if the expansion occurred before or after domestication. The results of the present study are consistent with an expansion that primarily occurred prior to domestication because the mtDNA haplotypes found in European and Asian wild boars did not form their own clusters but were intermingled with haplotypes found in domestic pigs, indicating that they originated from the same population expansion.     

The Tabby cat locus maps to feline chromosome B1

The Tabby markings of the domestic cat are unique coat patterns for which no causative candidate gene has been inferred from other mammals. In this study, a genome scan was performed on a large pedigree of cats that segregated for Tabby coat markings, specifically for the Abyssinian (Ta-) and blotched (tbtb) phenotypes. There was linkage between the Tabby locus and eight markers on cat chromosome B1. The most significant linkage was between marker FCA700 and Tabby (Z = 7.56, theta = 0.03). Two additional markers in the region supported linkage, although not with significant LOD scores. Pairwise analysis of the markers supported the published genetic map of the cat, although additional meioses are required to refine the region. The linked markers cover a 17-cM region and flank an evolutionary breakpoint, suggesting that the Tabby gene has a homologue on either human chromosome 4 or 8. Alternatively, Tabby could be a unique locus in cats.     

Regionally high rates of hybridization and introgression in German wildcat populations (Felis silvestris, Carnivora, Felidae)

While the western populations of the wildcat ( Felis silvestris silvestris ) in Germany come into contact with wildcats in France and Switzerland, the eastern distribution area is geographically completely isolated and consists of scattered subpopulations. To investigate population structure, evolutionary relationships and degree of hybridization with domestic cats we analysed the mitochondrial control region of 86 cats in combination with 11 microsatellite loci of 149 cats. According to our microsatellite data, German wildcats are divided into two separate populations corresponding to the western and eastern distribution areas. We found no indication of a further subdivision of the eastern population. German wildcat populations are genetically distinct from domestic cats in the main, but we identified 18.4% of the whole wildcat sample as being of hybrid origin, corresponding to 4.2% of the eastern and 42.9% of the western wildcat population, and 2.7% of the domestic cat sample. The mitochondrial haplotypes form a network of three connected clusters and reveal a high level of genetic diversity, especially within the eastern population. Our findings are explained at best in terms of continuous introgression between domestic cats and wildcat populations and differing degrees of recent hybridization in the various populations. Future conservation efforts should focus on preserving the existing gene flow between the isolated distribution areas, but also on preventing the spread of hybrids and limiting the habitat alterations that lead to increased contact with domestic cats. In conclusion we discuss possible evolutionary reasons for the still traceable genetic integrity of the wildcat despite its long history of interbreeding.     

Preserving genetic integrity in a hybridising world: are European Wildcats (Felis silvestris silvestris) in eastern France distinct from sympatric feral domestic cats?

We investigate the genetic profile of putative European Wildcats in north-eastern France, possessing the wildcat phenotype, but sampled in an area where they are sympatric with free-roaming domestic cats and, thus, are exposed to potential hybridisation. From a sample of 209 cats, the programme STRUCTURE clearly identified two distinct genetic clusters that corresponded to European Wildcats and domestic cats. The cats from these two clusters were clearly differentiated from each other (F _ST  = 0.16). However, the genotypes of some individual cats were split between the two clusters, indicative of genetic admixture. Our analysis demonstrates that a genetically distinct population of cats that possess the European Wildcat phenotype persists in north-eastern France, but that there is a low, yet real, risk of hybridisation with sympatric domestic cats. These European Wildcats warrant conservation efforts to protect their genetic integrity.     

European wildcat populations are subdivided into five main biogeographic groups: consequences of Pleistocene climate changes or recent anthropogenic fragmentation?

Extant populations of the European wildcat are fragmented across the continent, the likely consequence of recent extirpations due to habitat loss and over‐hunting. However, their underlying phylogeographic history has never been reconstructed. For testing the hypothesis that the European wildcat survived the Ice Age fragmented in Mediterranean refuges, we assayed the genetic variation at 31 microsatellites in 668 presumptive European wildcats sampled in 15 European countries. Moreover, to evaluate the extent of subspecies/population divergence and identify eventual wild × domestic cat hybrids, we genotyped 26 African wildcats from Sardinia and North Africa and 294 random‐bred domestic cats. Results of multivariate analyses and Bayesian clustering confirmed that the European wild and the domestic cats (plus the African wildcats) belong to two well‐differentiated clusters (average Ф_ST = 0.159, R_st  = 0.392, P > 0.001; Analysis of molecular variance [AMOVA]). We identified from c. 5% to 10% cryptic hybrids in southern and central European populations. In contrast, wild‐living cats in Hungary and Scotland showed deep signatures of genetic admixture and introgression with domestic cats. The European wildcats are subdivided into five main genetic clusters (average Ф_ST = 0.103, R_st  = 0.143, P > 0.001; AMOVA) corresponding to five biogeographic groups, respectively, distributed in the Iberian Peninsula, central Europe, central Germany, Italian Peninsula and the island of Sicily, and in north‐eastern Italy and northern Balkan regions (Dinaric Alps). Approximate Bayesian Computation simulations supported late Pleistocene–early Holocene population splittings (from c. 60 k to 10 k years ago), contemporary to the last Ice Age climatic changes. These results provide evidences for wildcat Mediterranean refuges in southwestern Europe, but the evolution history of eastern wildcat populations remains to be clarified. Historical genetic subdivisions suggest conservation strategies aimed at enhancing gene flow through the restoration of ecological corridors within each biogeographic units. Concomitantly, the risk of hybridization with free‐ranging domestic cats along corridor edges should be carefully monitored.     

Molecular genetics and evolution of melanism in the cat family

Melanistic coat coloration occurs as a common polymorphism in 11 of 37 felid species and reaches high population frequency in some cases but never achieves complete fixation. To investigate the genetic basis, adaptive significance, and evolutionary history of melanistic variants in the Felidae, we mapped, cloned, and sequenced the cat homologs of two putative candidate genes for melanism (ASIP [agouti] and MC1R) and identified three independent deletions associated with dark coloration in three different felid species. Association and transmission analyses revealed that a 2 bp deletion in the ASIP gene specifies black coloration in domestic cats, and two different "in-frame" deletions in the MC1R gene are implicated in melanism in jaguars and jaguarundis. Melanistic individuals from five other felid species did not carry any of these mutations, implying that there are at least four independent genetic origins for melanism in the cat family. The inferred multiple origins and independent historical elevation in population frequency of felid melanistic mutations suggest the occurrence of adaptive evolution of this visible phenotype in a group of related free-ranging species.     

Genetic analysis shows low levels of hybridization between African wildcats (Felis silvestris lybica) and domestic cats (F. s. catus) in South Africa

Hybridization between domestic and wild animals is a major concern for biodiversity conservation, and as habitats become increasingly fragmented, conserving biodiversity at all levels, including genetic, becomes increasingly important. Except for tropical forests and true deserts, African wildcats occur across the African continent; however, almost no work has been carried out to assess its genetic status and extent of hybridization with domestic cats. For example, in South Africa it has been argued that the long‐term viability of maintaining pure wildcat populations lies in large protected areas only, isolated from human populations. Two of the largest protected areas in Africa, the Kgalagadi Transfrontier and Kruger National Parks, as well as the size of South Africa and range of landscape uses, provide a model situation to assess how habitat fragmentation and heterogeneity influences the genetic purity of African wildcats. Using population genetic and home range data, we examined the genetic purity of African wildcats and their suspected hybrids across South Africa, including areas within and outside of protected areas. Overall, we found African wildcat populations to be genetically relatively pure, but instances of hybridization and a significant relationship between the genetic distinctiveness (purity) of wildcats and human population pressure were evident. The genetically purest African wildcats were found in the Kgalagadi Transfrontier Park, while samples from around Kruger National Park showed cause for concern, especially combined with the substantial human population density along the park's boundary. While African wildcat populations in South Africa generally appear to be genetically pure, with low levels of hybridization, our genetic data do suggest that protected areas may play an important role in maintaining genetic purity by reducing the likelihood of contact with domestic cats. We suggest that approaches such as corridors between protected areas are unlikely to remain effective for wildcat conservation, as the proximity to human settlements around these areas is projected to increase the wild/domestic animal interface. Thus, large, isolated protected areas will become increasingly important for wildcat conservation and efforts need to be made to prevent introduction of domestic cats into these areas.     

TEMPORAL ALLOZYME FREQUENCY CHANGES IN DENSITY FLUCTUATING POPULATIONS OF WILLOW GROUSE (LAGOPUS LAGOPUS L.)

The population density of willow grouse (Lagopus lagopus L.) in northern Scandinavia changes in synchrony with the cyclic density variations in populations of microtine rodents. To assess the genetic changes accompanying the variations in population number, allozyme variation was studied at 23 loci in 640 willow grouse, representing four mainland and one island locality sampled during high and low population density. The average heterozygosity (H = 8.3%) and proportion of polymorphic loci (P = 26%) is not lower in willow grouse than in avian species with a more stable demography; the recurrent population density changes do not appear to affect drastically the long term effective population size, presumably because of extensive migration. Significant allele frequency differences were found both between populations and between different density phases. The genetic distance (D; Nei, 1972) was, in about 50% of the cases, larger between two consecutive time periods than between two localities in a certain year. Spatial and temporal allele frequency variation each represented around 3% of the gene diversity. The temporal heterogeneity may be caused by nonrandom sampling of family groups, rather than drift of allele frequencies between generations due to small effective population size, as has been suggested for microtine species.     

Comparative analysis of the within-population genetic structure in wild cherry (Prunus avium L.) at the self-incompatibility locus and nuclear microsatellites

Gametophytic self-incompatibility (SI) systems in plants exhibit high polymorphism at the SI controlling S-locus because individuals with rare alleles have a higher probability to successfully pollinate other plants than individuals with more frequent alleles. This process, referred to as frequency-dependent selection, is expected to shape number, frequency distribution, and spatial distribution of self-incompatibility alleles in natural populations. We investigated the genetic diversity and the spatial genetic structure within a Prunus avium population at two contrasting gene loci: nuclear microsatellites and the S-locus. The S-locus revealed a higher diversity (15 alleles) than the eight microsatellites (4-12 alleles). Although the frequency distribution of S-alleles differed significantly from the expected equal distribution, the S-locus showed a higher evenness than the microsatellites (Shannon's evenness index for the S-locus: E = 0.91; for the microsatellites: E = 0.48-0.83). Also, highly significant deviations from neutrality were found for the S-locus whereas only minor deviations were found for two of eight microsatellites. A comparison of the frequency distribution of S-alleles in three age-cohorts revealed no significant differences, suggesting that different levels of selection acting on the S-locus or on S-linked sites might also affect the distribution and dynamics of S-alleles. Autocorrelation analysis revealed a weak but significant spatial genetic structure for the multilocus average of the microsatellites and for the S-locus, but could not ascertain differences in the extent of spatial genetic structure between these locus types. An indirect estimate of gene dispersal, which was obtained to explain this spatial genetic pattern, indicated high levels of gene dispersal within our population (sigma(g) = 106 m). This high gene dispersal, which may be partly due to the self-incompatibility system itself, aids the effective gene flow of the microsatellites, thereby decreasing the contrast between the neutral microsatellites and the S-locus.     

秦岭细鳞鲑人工繁育群体与野生群体遗传变异分析

研究利用线粒体DNA（细胞色素b基因序列和D-loop区序列）序列对秦岭细鳞鲑（Brachymystax lenok tsinlingensis）野生群体和人工繁育群体的种群遗传结构进行了分析。结果表明, 在86个个体扩增出的线粒体D-loop区730 bp片段中, A+T含量（63.5%）明显高于G+C含量（36.5%）。Cyt b基因序列扩增1141 bp, A+T含量（52.8%）明显高于G+C含量（47.2%）。野生群体43个个体共检测到18个单倍型, 繁育群体43个个体中共检测到24个单倍型, 两个群体共享8个单倍型; 秦岭细鳞鲑野生群体的单倍型多样性和核苷酸多样性（h=0.9070.026; =0.002870.00074）低于繁育群体（h=0.9170.035; =0.003490.00083）, AMOVA分析显示, 98.37%的分子差异位于群体内, 1.63%的分子差异位于群体间, 两群体之间的遗传分化水平较低（Fst=0.01631, P=0.1075; Nm=30.16）。采用邻接法构建的系统发育树和单倍型网络图分析表明, 各群体内的个体不形成单系群, 两者之间互有交叉。总之, 秦岭细鳞鲑野生群体与繁育群体之间基因交流充分, 未出现遗传分化。