Microsatellite variability and heterozygote deficiency in the arctic-alpine Alaskan wheatgrass (Elymus alaskanus) complex.

Genetic variation in the allotetraploid grass Elymus alaskanus complex was assessed using microsatellites in seven populations from Canada, Greenland, and the U.S.A. Microsatellite variation was compared with allozyme and RAPD variation. Our results indicated that E. alaskanus was highly homozygous but also highly variable. The polymorphic loci ranged from 50 to 100% with a mean of 78.6%, and the mean number of allele per locus was 3.14. Average expected heterozygosity value (HE, gene diversity) varied across populations and ranged from 0.244 to 0.651 with mean of 0.414. The mean value of HE across Canadian populations (0.517) was significantly higher than that across populations in Greenland (0.367). The correlation between allozyme and microsatellite gene diversity value (HE) showed a high positive correlation (r = 0.68), but between RAPD and microsatellite showed a low positive correlation (r = 0.08). Populations were highly differentiated, with 38% of variation among populations. Interpopulation genetic distance showed no association with geographic distance between the population sites of origin. A Hardy-Weinberg exact test for all loci and all populations reveals a significant heterozygote deficiency. Possible explanations for heterozygote deficiency are discussed.     

云南松居群遗传学研究的等位酶分析方法

针对１５个云南松Ｐｉｎｕｓｙｕｎｎａｎｅｎｓｉｓ居群,开展了１４种酶系统的水平切片淀粉凝胶电泳实验,在谱带遗传分析的基础上确定了３３个等位酶位点及其等位基因。其中有３２个等位酶位点是多态的（有２个以上的等位基因）,只有一个单态位点Ｄｉａ－４。有３个等位基因的位点有Ｌａｐ－１、Ｌａｐ－２、Ａａ－３、Ｓｋｄ－１、Ｓｋｄ－２、Ａｄｈ－１、Ａｄｈ－３、Ｇｄｈ、Ｐｇｄ－１、Ｐｇｍ－１、Ｐｇｍ－３、Ｐｇｉ－１、Ｐｇｉ－３、Ｍｄｈ－１、Ｍｅ、Ｇ６ｐｄ、Ｄｉａ－１、Ｔｐｉ－１、Ｔｐｉ－２、Ｔｐｉ－３和Ｔｐｉ－４,有４个等位基因的位点有Ｓｋｄ－３、Ａｄｈ－２、Ｐｇｄ－２、Ｍｄｈ－２、Ｍｄｈ－３、Ｍｄｈ－４和Ｄｉａ－２,有５个等位基因的位点有Ａａｔ－１和Ｄｉａ－３。云南松居群的等位基因平均数Ａ＝２１,在松属中居于中上水平。本研究揭示了云南松居群酶位点及其等位基因带谱的变异式样,为松属植物的遗传多样性研究提供了一批酶位点及其等位基因的参考图谱     

Genetic variation and differentiation in Nordic populations of Elymus alaskanus (Scrib. ex Merr.) Löve (Poaceae)

 To gain information on the extent and nature of genetic variation in Elymus alaskanus, levels and distribution of genetic variation were assessed within and among 13 populations originating from Iceland, Norway, Sweden and Russia using allozymes. The results showed that four (30.7%) of the 13 loci were polymorphic within the species, while the mean percentage of polymorphic loci within the populations was 1.9%. The mean number of alleles per locus for the species was 1.8 and 1.02 across the populations. Genetic diversity at the species level was low (H _es=0.135), and mean population diversity was notably lower (H _ep=0.005). A high degree of genetic differentiation was observed among populations. The salient points emerging from this study are: (1) statistically significant differences were found in allele frequencies among populations for every polymorphic locus (P<0.001), (2) the high mean coefficient of gene differentiation (G _ST) showed that 95% of the total allozyme variation was attributable to differences among populations, and (3) relatively high genetic distances between the populations were obtained (mean D=0.16). The Norwegian populations had the highest genetic diversity as compared with the other populations. Geographical comparisons revealed three different groups of populations clearly differentiated, i.e. Scandinavia (Norway and Sweden), Iceland and Russia. Cluster and principal coordinates analyses revealed the same genetic patterns of relationships among populations. Generally, this study indicates that E. alaskanus contains low allozymic variation in its populations. The implications of these results for the conservation of the species are discussed. Received: 23 October 1998 / Accepted: 19 December 1998     

Genetic diversity and population structure of Yucca filamentosa (Agavaceae)

Using 19 allozyme loci we studied genetic diversity in 18 populations of Yucca filamentosa (Agavaceae) from the southeastern United States. Of the 19 loci surveyed, 17 (89.5%) were polymorphic in at least one of the populations sampled. There was considerable variation among populations in the percentage of polymorphic loci (range = 31.6-84.2%, mean = 67.6%). Similar heterogeneity among populations was observed for mean number of alleles per polymorphic locus (range = 2.0-3.0; mean = 2.48) and mean expected heterozygosity (range = 0.113-0.288; mean = 0.213). On average, 83% of the total genetic diversity was found within populations. Duplications of three allozyme loci were detected in several populations. The life-history characteristics of Y. filamentosa (a long-lived, semiwoody, predominantly outcrossing monocot with a large geographical range) may contribute to the maintenance of such high levels of genetic diversity. These results contradict expectations of the genetic structure of Y. filamentosa based on observations of the dispersal and pollination behavior of its sole pollinator, Tegeticula yuccasella, the yucca moth.     

Microsatellite polymorphism and genetic differentiation in three Norwegian populations of Elymus alaskanus (Poaceae)

 Variation at seven microsatellite loci was investigated in three local E. alaskanus populations from Norway and microsatellite variation was compared with allozyme variation. The percentage of polymorphic loci was 81%, the mean number of alleles per polymorphic locus was 5.7 and expected heterozygosity was 0.37. An F-statistic analysis revealed an overall 48% deficit of heterozygotes over Hardy-Weinberg expectations. Gene diversity is mainly explained by the within population component. The averaged between population differentiation coefficient, F _st , over 7 loci is only 0.13, which accounts for only 13% of the whole diversity and was contrary to allozyme analysis. The mean genetic distance between populations was 0.12. However, a χ² -test showed that allele frequencies were different (p < 0.05) among the populations at 5 of the 7 loci. In comparison with the genetic variation detected by allozymes, microsatellite loci showed higher levels of genetic variation. Microsatellite analysis revealed that population H10576 possesses the lowest genetic variation among the tested three populations, which concur with allozyme analysis. The dendrogram generated by microsatellites agreed very well with allozymic data. Our results suggest that natural selection may be an important factor in shaping the genetic diversity in these three local E. alaskanus populations. Possible explanations for deficit heterozygosity and incongruence between microsatellites and allozymes are discussed. Received November 6, 2001; accepted April 24, 2002 Published online: November 14, 2002 Addresses of the authors: Genlou Sun (e-mail: Genlou.sun@STMARYS.CA), Biology Department, Saint Mary's University, Halifax. Nova Scotia, B3H 3C3, Canada. B. Salomon, R. von Bothmer, Department of Crop Science, The Swedish University of Agricultural Sciences, P.O. Box 44, SE-230 53, Alnarp, Sweden.     

Concordance of genetic divergence among sockeye salmon populations at allozyme, nuclear DNA, and mitochondrial DNA markers

Abstract.— We examined genetic variation at 21 polymorphic allozyme loci, 15 nuclear DNA loci, and mitochondrial DNA in four spawning populations of sockeye salmon ( Oncorhynchus nerka ) from Cook Inlet, Alaska, to test for differences in the patterns of divergence among different types of markers. We were specifically interested in testing the suggestion that natural selection at allozyme loci compromises the effectiveness of these markers for describing the amount and patterns of gene flow among populations. We found concordance among markers in the amount of genetic variation within and among populations, with the striking exception of one allozyme locus ( sAH ), which exhibited more than three times the amount of among-population differentiation as other loci. A consideration of reports of discordance between allozymes and other loci indicates that these differences usually result from one or two exceptional loci. We conclude that it is important to examine many loci when estimating genetic differentiation to infer historical amounts of gene flow and patterns of genetic exchange among populations. It is less important whether those loci are allozymes or nuclear DNA markers.     

Population genetic structure and differentiation of Anthoxanthum alpinum in the subalpine-alpine ecocline of Swiss Alps

Allozyme variation in 6 enzyme systems coding 10 loci was estimated for 18 subpopulations of Anthoxanthum alpinum from three altitudinal transects in two localities of the Swiss Alps. Mean proportions of polymorphic loci (95% criterion), average number of alleles per locus, and mean expected heterozygosity were 64.9%, 2.37 and 0. 252, respectively. Mean genetic distance among populations was 0.011, and 79% of the genetic variation resided within populations. Based on allozyme analysis, marginal subpopulations appeared to have similar level of genetic variability to central subpopulations. Relatively high genetic differentiation, low gene flow values and small neighbourhood sizes suggested that inbreeding followed by genetic drift was possible causes of lowgenetic variability in Arpette A. alpinum populations.     

广西石灰岩地区蜈蚣蕨居群的遗传多样性研究

采用等位酶分析方法 ,研究了广西石灰岩地区蜈蚣蕨居群的遗传多样性 ,分析了其空间变化趋势。检测了 8个酶系统 ,1 5个酶位点。分析结果表明 :广西石灰岩地区蜈蚣蕨居群遗传多样性程度较高 ,每个位点的等位基因平均数为 1 .6 7,多态位点为 5 7.78% ,平均期望杂合度为 0 .2 4 9。蜈蚣蕨居群的遗传组成在居群间有一定的差异 ,但差异的程度并不与空间距离成正比     

阿尔卑斯山高山-亚高山过渡区高山黄花茅的群体遗传结构和分化研究

应用等位酶分析,在瑞士阿尔卑斯山的阿尔拜特(Arpette)和拜阿尔普(Belalp),沿三个不同的海拔梯度,研究了高山黄花茅3个自然居群的遗传变异和分化。研究结果表明,平均的多态性位点比例为64．9％,每个位点平均等位基因数为2．37,平均期望杂合性为0．252。亚居群间平均的遗传距离为0．011,发现79％的遗传变异存在于居群内。基于等位酶分析,边缘亚居群与中心亚居群似乎有类似的遗传变异性。相对比较高的遗传分化、低的亚居群间基因流和小的邻居大小值暗示,近交和随后的遗传漂变可能是导致阿尔拜特黄花茅居群遗传变异性较低的主要原因。     

Evolutionary implications of allozyme and RAPD variation in diploid populations of dioecious buffalograss Buchloë dactyloides

Buffalograss, Buchloë dactyloides, is widely distributed throughout the Great Plains of North America, where it is an important species for rangeland forage and soil conservation. The species consists of two widespread polyploid races, with narrowly endemic diploid populations known from two regions: central Mexico and Gulf Coast Texas. We describe and compare the patterns of allozyme and RAPD variation in the two diploid races, using a set of 48 individuals from Texas and Mexico (four population samples of 12 individuals each). Twelve of 22 allozyme loci were polymorphic, exhibiting 35 alleles, while seven 10-mer RAPD primers revealed 98 polymorphic bands. Strong regional differences were detected in the extent of allozyme polymorphism: Mexican populations exhibited more internal gene diversity (H_e= 0.20, 0.19) than did the Texan populations (H_e= 0.08, 0.06), although the number of RAPD bands in Texas (n= 62) was only marginally smaller than in Mexico (n= 68). F-statistics for the allozyme data, averaged over loci, revealed strong regional differentiation (mean F_RT=+ 0.30), as well as some differentiation among populations within regions (mean F_PR=+ 0.09). In order to describe and compare the partitioning of genetic variation for multiple allozyme and RAPD loci, we performed an Analysis of Molecular Variance (AMOVA). AMOVA for both allozyme and RAPD data revealed similar qualitative patterns: large regional differences and smaller (but significant) population differences within regions. RAPDs revealed greater variation among regions (58.4% of total variance) than allozymes (45.2%), but less variation among individuals within populations (31.9% for RAPDs vs. 45.2% for allozymes); the proportion of genetic variance among populations within regions was similar (9.7% for RAPDs vs. 9.6% for allozymes). Despite this large-scale concordance of allozyme and RAPD variation patterns, multiple correlation Mantel techniques revealed that the correlations were low on an individual by individual basis. Our findings of strong regional differences among the diploid races will facilitate further study of polyploid evolution in buffalograss.     

Genetic Diversity in Cymophyllus fraserianus (Cyperaceae), a Rare Monotypic Genus

Cymophyllus fraserianus (Fraser's sedge) is a rare perennial evergreen herb found in late-successional forest communities in the Appalachian Mountains of the U.S. Genetic diversity was assessed at 19 allozyme loci for 12 populations sampled from the southern and central portions of the range of this primitive monotypic genus. Species variation was comparable to that found for other narrowly distributed species, although mean population genetic diversity was somewhat higher. Sixteen of the 19 loci (84%) were polymorphic, with a mean of 46% polymorphic within populations. On average, 2.7 alleles were detected per polymorphic locus. Genetic diversity within populations (Hep) averaged 0.113, whereas species' genetic diversity (Hes) was 0.131. Although a twofold range of within-population genetic diversity (Hep = 0.075-0.158) was found, less than 13% of the genetic variation was distributed among populations (G(ST) = 0.129). An indirect estimate of historical levels of gene flow (Nm = 1.69) was consistent with the high mean genetic identity (mean I = 0.96) found between populations. Despite the relictual nature of C. fraserianus, its rarity and fragmented distribution, genetic diversity within the genus is typical of herbs with similar life-history characteristics. No association was found between geographic and genetic distances between populations (r = -0.01; p > 0.9), suggesting that present day populations are relatively isolated.     

Allozyme differentiation of populations of the dogwhelk Nucella lapillus, (L.): the relative effects of geographic distance and variation in chromosome number

Geographic patterns of genie differentiation were compared with differentiation between karyotypes in the intertidal snail Nucella lapillus. Samples from 24 sites covering the species range in Europe and North America were analysed for allozyme variation at 16 soluble enzyme loci. Two homokaryotypes have been identified with diploid numbers 2n = 26 and 2n= 36 (variation is Robertsonian and hybrids have intermediate chromosome numbers) and samples were classified (on the basis of published data) according to karyotype. Group 1 consisted of samples from three English Channel populations of higher chromosome number (on average 2n > 32) and Group 2 consisted of the remaining 21 samples (presumed to be 2n= 26). Karyotype variation accounts for roughly the same amount of the absolute allozyme variance as geographic variation (46.3 °, and 53.7°, respectively). Yet the patterns of differentiation seen between karyotypes and with geographic separation are very different. In samples classified as 2n= 26 (Group 2), while there is a significant amount of heterogeneity (F_ST per locus averaged 0.128 for 10 polymorphic loci), allozyme variation occurs independently at different loci so mean genetic identity (Nei) is high: 0.972. There is only a slight decline in genetic identity with distance (genetic identity averaged 0.965 for amphi-atlantic comparisons) indicating that passive transport of juveniles or adults may contribute significantly to gene flow. Conversely, allozyme variation between karyotypes was concordant. High chromosome number populations possessed a suite of alleles at four allozyme loci (Esl-3, Lap-2, Mdh-1 and Pep-2) which were absent or rare in Group 2 samples resulting in high F_ST values for these loci (from 0.294 to 0.472) when karyotypic classes were combined. Consequently the mean genetic identity between these Robertsonian races is low, 0.856, and falls within the range more usually associated with congeneric comparisons than with con-specific comparisons. The mechanisms maintaining this genie difference are unclear. However the distribution of the karyotypes and physiological and morphological differences (in shell shape) between them strongly suggest that karyotypic variation in Nucella is adaptive.     

GENETIC DIVERSITY AND POPULATION STRUCTURE IN CAMELLIA JAPONICA L. (THEACEAE)

Camellia japonica is a widespread and morphologically diverse tree native to parts of Japan and adjacent islands. Starch gel electrophoresis was used to score allelic variation at 20 loci in seeds collected from 60 populations distributed throughout the species range. In comparison with other plant species, the level of genetic diversity within C. japonica populations is very high: 66.2% of loci were polymorphic on average per population, with a mean number of 2.16 alleles per locus; the mean observed and panmictic heterozygosities were 0.230 and 0.265, respectively. Genotypic proportions at most loci in most populations fit Hardy-Weinberg expectations. However, small heterozygote deficiencies were commonly observed (mean population fixation index = 0.129). It is suggested that the most likely cause of the observed deficiencies is population subdivision into genetically divergent subpopulations. The overall level of population differentiation is greater than is typically observed in out-breeders: The mean genetic distance and identity (Nei's D and I) between pairs of populations were 0.073 and 0.930, respectively, and Wright's Fst was 0.144. Differences among populations appeared to be manifested as variation in gene frequencies at many loci rather than variation in allelic composition per se. However, the patterns of variation were not random. Reciprocal clinal variation of gene frequencies was observed for allele pairs at six loci. In addition, principal components analysis revealed that populations tended to genetically cluster into four regions representing the geographic areas Kyushu, Shikoku, western Honshu, and eastern Honshu. There was a significant relationship between genetic and geographic distance (r = 0.61; P < 0.01). Analysis of variance on allozyme frequencies showed that there was approximately four times as much differentiation among populations within regions, as among regions. It is likely that the observed patterns of population relationships result from the balance between genetic drift in small subpopulations and gene flow between them.     

Genetic differentiation of pink salmon oncorhynchus gorbuscha Walbaum in the Asian part of the range

Genetic variation at 19 allozyme (including 11 polymorphic) and 10 microsatellite loci was examined in the population samples of odd- and even-broodline pink salmon from the southern part of Sakhalin Island, Southern Kuril Islands, and the northern coast of the Sea of Okhotsk. The estimates of relative interpopulation component of genetic variation over the allozyme loci, per broodline, were on average 0.43% (GST), while over the microsatellite loci it was 0.26% (the theta(ST) coefficient, F-statistics based on the allele frequency variance), and 0.90% (the rho(ST) coefficient, R-statistics based on the allele size variance). The values of interlinear component constituted 2.34, 0.31, and 1.05% of the total variation, respectively. Using the allozyme loci, statistically significant intralinear heterogeneity was demonstrated among the regions, as well as among the populations of Southern Sakhalin Island. Multivariate scaling based on the allozyme data demonstrated regional clustering of the sample groups, representing certain populations during the spawning run or in different years. Most of the microsatellite loci examined were found to be highly polymorphic (mean heterozygosity > 0.880). The estimates of interlinear, interregional, and interpopulation variation over these loci in terms of theta(ST) values were substantially lower than in terms of rho(ST) values. Regional genetic differentiation, mostly expressed at the allozyme loci among the populations from the northern and southern parts of the Sea of Okhotsk (i.e., between the Sakhalin and Kuril populations), was less expressed at the microsatellite loci. The differentiation between these regions observed can be considered as the evidence in favor of a large-scale isolation by distance characterizing Asian pink salmon. It is suggested that in pink salmon, low genetic differentiation at neutral microsatellite loci can be explained by extremely high heterozygosity,of the loci themselves, as well as by the migration gene exchange among the populations (the estimate of the genetic migration coefficient inferred from the "private" allele data constituted 2.6 to 3.4%), specifically, by the ancient migration exchange, which occurred during postglacial colonization and colonization of the range.     

Genetic variation in rural and urban populations of Epipactis helleborine (L.) Crantz. (Orchidaceae) in Britain

Genetic variation in Epipactis helleborine in the British Isles was assessed using starch gel electrophoresis of isozymes; 273 individuals were sampled from 13 populations and examined for genetic variation using eight enzyme systems encoded for by 13 loci. Overall, 46% of the loci examined were polymorphic, with an average of 1.69 alleles per locus. Within populations, a mean of 33% of the loci were polymorphic, with a mean number of 1.46 alleles per locus. Levels of genetic variation were compared between urban and well established rural populations to assess the genetic consequences of colonization of the urban sites. The average levels of genetic variation detected in urban populations were lower than that found in rural populations, although there was a much greater range of variation among the urban populations. Large urban populations actually have patterns of variation similar to rural populations and show evidence of multiple founders. This indicates that the high dispersibility of Epipactis seeds can in some cases overcome the predicted loss of genetic variation associated with founder effects during colonization. Small urban populations, however, show significantly lower levels of genetic variation compared with these large urban populations and the rural populations, and it seems likely that this is attributable to single founding events and/or genetic drift.     

Microsatellite analysis of genetic diversity and population genetic structure of a wild rice (<Emphasis Type="Italic">Oryza rufipogon</Emphasis> Griff.) in China

Genetic diversity and population genetic structure of natural Oryza rufipogon populations in China were studied based on ten microsatellite loci. For a total of 237 individuals of 12 populations collected from four regions, a moderate to high level of genetic diversity was observed at population levels with the number of alleles per locus ( A) ranging from 2 to 18 (average 10.6), and polymorphic loci ( P) from 40.0% to 100% (average 83.3%). The observed heterozygosity ( H(O)) varied from 0.163 to 0.550 with the mean of 0.332, and the expected heterozygosity ( H(E)) from 0.164 to 0.648 with the mean of 0.413. The level of genetic diversity for Guangxi was the highest. These results are in good agreement with previous allozyme and RAPD studies. However, it was unexpected that high genetic differentiation among populations was found ( R(ST) = 0.5199, theta = 0.491), suggesting that about one-half of the genetic variation existed between the populations. Differentiation (pairwise theta) was positively correlated with geographical distance ( r = 0.464), as expected under the isolation by distance model. The habitat destruction and degradation throughout the geographic range of O. rufipogon may be the main factor attributed to high genetic differentiation among populations of O. rufipogon in China.     

Characterization of genetic diversity in core collection accessions of wild barley,Hordeum vulgare ssp. spontaneum

Genetic variability in the 143 core accessions of wild barley, Hordeum vulgare ssp. spontaneum, was assessed by allozyme analysis. A total of 34 alleles were detected at ten isozyme loci. All loci were polymorphic except Pgd-1, which was monomorphic. Est-2 and Est-4 were the most diverse loci, with genetic diversity values of 0.747 and 0.686, respectively. The comparison of the results with those of previous studies indicates that all alleles occurring in cultivated and wild barley are observed in this set of the wild Barley Core Collection. Only one allele (Pgd-1 Tj) was absent. It is noteworthy that one new allele at the Ndh-2 locus and another new allele at Aco-2 locus were first detected in the present study. Nine of the 34 alleles were rare and detected only in one to four accessions. The genetic similarities among the 143 accessions ranged from 0.18 to 1.00. Data analysis based on clustering and principal coordinate analysis showed that a high level of genetic variability exists in this set of core accessions, and indicated that some duplication probably exists in this set core based on the present study.     

Allozyme diversity in the apomictic vine Bryonia alba (cucurbitaceae): potential consequences of multiple introductions

Bryonia alba (Cucurbitaceae) is a Eurasian herbaceous vine that spreads vegetatively through the production of many stems from a large, tuberous root. The only known U.S. populations of this aggressive apomict are in Idaho, Montana, Utah, and Washington and likely stem from deliberate (and subsequent accidental) introductions. To assess levels and patterns of genetic diversity of B. alba across its introduced range, 23 populations were analyzed for allozyme variation using 12 enzyme systems. On average, 14.9% of loci are polymorphic per population (1.19 alleles per locus)—low values compared to other vascular plant taxa. Mean percent polymorphic loci differed among regions, with the highest values in the Washington and northern Idaho region (20.2%) and Montana (19.0%) and lower values in populations from the Utah and southern Idaho region (7.4%). Observed heterozygosity exceeded that expected at Hardy-Weinberg equilibrium in six of 23 populations, and a statistically significant excess of heterozygosity was detected at Pgm-1 in 18 of 23 populations. The level of population differentiation is high (G_ST = 0.544); however, the level of differentiation among populations within regions is much lower. These results are consistent with the genetic variation and structure expected for an apomict. Based on the level of genetic differentiation among populations, the current disjunct distribution of B. alba in its new range results from two, and possibly three, separate introductions in the western United States. These introductions may stem, in part, from the vine's 19th century use as a medicinal and ornamental plant.     

Patterns of allozyme diversity in the threatened plant Erigeron parishii (Asteraceae)

Thirty-one occurrences of Erigeron parishii, a narrowly endemic plant threatened by mining, were sampled for allozyme diversity. This taxon held considerable genetic variation at the 14 allozyme loci surveyed. Species (e.g., alleles per locus [A] = 4.3 and proportion of polymorphic loci [P] = 0.64) and population (e.g., A = 2.15 [SD = 0.3] and P = 0.53 [SD = 0.12]) genetic diversity measures were higher than expected for narrowly endemic plant taxa. The proportion of polymorphic loci and numbers of alleles per locus indicated that E. parishii has not experienced severe or long-lasting population bottlenecks. Within-population f indicated low to moderate levels of inbreeding. Populations were only moderately differentiated (theta-p = 0.12), suggesting either that there is substantial gene flow among populations or that populations have not been isolated long enough to detect effects of genetic drift. There was no significant differentiation among populations in different vegetation types nor was there a relationship between genetic distance and geographic distance among sites. Continued fragmentation by mining activities would isolate populations, disrupting gene flow, exacerbating loss of diversity, and increasing inbreeding in the remaining fragments. Protection of large, interconnected populations throughout the range of the taxon is warranted to maintain processes that have sustained the observed diversity.     

Interspecific genetic variability of the oyster mushroom Pleurotus ostreatus as revealed by allozyme gene analysis

Allozyme variation in natural populations of basidiomycetes fungus Pleurotus ostreatus (88 individuals) from three regions of central Russia was studied. The species was shown to have 92.86% of polymorphic allozyme loci and expected heterozygosity He = 0.49. The mean number of alleles per locus was 3.5. The genetic differences among populations were supported by F-statistics (FST = 0.750). The low level of inbreeding (FIS = 0.018) suggests that the P. ostreatus populations are panmictic, and the main reproduction mode involves basidiospores dispersing at long distances. Using cluster analysis, geographically isolated populations and intersterile groups were differentiated within the complex P. ostreatus species.