Genetic Variation and Clonal Diversity of the Two Divergent Types of Clonal Populations of Leymus chinensis Tzvel on the Song Liao Steppe in the West of Northeastern China

The genetic variation and clonal diversity of two divergent types (grey-green and yellow-green) of clonal populations ofLeymus chinensis Tzvel at 14 loci were compared. Total gene diversity (HT) and the coefficient of genetic differentiation (GsT) were all higher for the yellow-green type (HT = 0.270; GsT = 0.186)than for the grey-green type (HT = 0.250; GsT = 0.157) of L. chinensis. Rare alleles usually occurred as heterozygotes rather than homozygotes and significant deviations from Hardy-Weinberg equilibrium were found only at a few loci. This indicated that these two types of populations were mainly out-crossing. Clonal diversity, evenness of clones, and mean clone size were not significantly different between the two types.We found that differences between the clone size and genetic variation of the yellow-green type of popula tions occurred with different climate and habitat population groups. However, for the grey-green type of populations, these genetic variations decreased under conditions of different climate and habitat popula tion groups.     

Allozyme Diversity in Populations of Cymbidium goeringii (Orchidaceae)

Abstract: Using 14 allozyme loci, we investigated levels of genetic diversity within populations, and degree of genetic divergence among 24 populations of Cymbidium goeringii (Orchidaceae) in Korea and Japan. Cymbidium goeringii maintains high levels of genetic diversity both at population (mean expected heterozygosity, H _e = 0.238) and species levels (0.260). Means of H _e found in 24 populations were not significantly different from each other. About 90 % of the total variation in the species is common to all populations (mean G _ST = 0.108). No unique allele was found in any population. The indirect estimate of gene flow based on the mean G _ST was high ( Nm = 2.06). Nei's genetic identities for pairs of populations had high values (mean = 0.974 [SD = 0.013]). The Mantel-Z test showed a significant correlation between genetic distance and geographic distance. However, the mean G _ST value between 17 populations in Korea and seven Japanese populations was relatively low (0.029), even though the land connection between the southern Korean peninsula and southern Japanese archipelagos has not existed since the middle Pleistocene. Large numbers of small seeds of C. goeringii might travel long distances by wind from populations to populations both in Korea and Japan, increasing genetic diversity within populations and maintaining low genetic differentiation among populations.     

松嫩草地两种趋异型羊草克隆构型特征比较

This paper studied the clonal architecture of two divergent Leyrnus chinensis types (grey-green type and yellowgreen type) in Songnen grassland, and compared their internode length, spacer length, interbranching length, interbranching angle, and ramet population density and height under the same habitat. The results showed that there was no significant difference in these clonal characteristics except spacer length and ramet population density between the two types of L. chinensis, and yellow-green type, with less spacer length and more ramet density than grey-green type, should be more adaptable to the resourceful habitat. Moreover, the V-indices of the clonal architecture of two divergent L. chinensis types were all close to 1, and the difference was not significant. Therefore, both of the two types belonged to typical guerilla clonal plant.     

Allozyme variability in brown trout Salmo trutta in Chile

1. Brown trout ova were imported during the last century from different locations in Europe to establish populations in Chilean rivers (South America). The rivers are currently occupied by naturalized populations that have adapted to very different environmental conditions, such as areas of semi-desert in the north, or rainy and cold areas in the south.
2. In this first study in this geographical area, electrophoretic variability of proteins encoded by twenty-five loci was screened in seven populations from northern to southern Chile.
3. The results show significant heterogeneity of allelic frequencies between populations in seven of eleven polymorphic loci detected. The estimated value of genetic diversity 0.1274 ( H _T) is higher than that observed in populations from areas of natural distribution of this species. However, only 12.64% of this genetic diversity was found between samples ( G _ST), indicating a low genetic divergence among Chilean populations. The observed associations among the Chilean and 'modern' group of European populations suggests the probable origin of the new populations.     

Reproductive biology of a mycoheterotrophic species, Burmannia wallichii (Burmanniaceae)

The breeding system of a mycoheterotrophic species, Bumannia wallichii (Miers) Hook. f. (Burmanniaceae), is assessed using field observations, floral anatomy, pollen histochemistry and isozyme electrophoresis. The structure of the flower effectively prevents pollinators from accessing the stamens, and no pollinators were observed visiting natural populations in Hong Kong. The pollen is starch-rich but lipid-poor. Analysis of isozyme variation revealed a small proportion of polymorphic loci, a low level of total heterozygosity ( H _T= 0.1972), and a very high overall fixation index of populations ( F _IT= 0.6602). These results strongly suggest that B. wallichii is predominantly self-pollinated. The coefficient of gene differentiation ( G _ST) is low (0.05), although it is suggested that this is due to genetic homogenization of populations consonant with the formation of numerous tiny 'diaspora' seeds that are wind dispersed.     

Population divergence in the amphicarpic species Amphicarpaea edgeworthii Benth. (Fabaceae): microsatellite markers and leaf morphology

Comparative analyses of the genetic differentiation in microsatellite markers ( F _ST) and leaf morphology characters ( Q _ST) of Amphicarpaea edgeworthii Benth. were conducted to gain insight into the roles of random processes and natural selection in the population divergence. Simple sequence repeat analyses on 498 individuals of 19 natural populations demonstrate that a significant genetic differentiation occurs among populations (mean F _ST = 0.578), and A. edgeworthii is a highly self-fertilized species (mean selfing rate s  = 0.989). The distribution pattern of genetic diversity in this species shows that central populations possess high genetic diversity (e.g. population WL with H _E = 0.673 and population JG with H _E = 0.663), whereas peripheral ones have a low H _E as in population JD (0.011). The morphological divergence of leaf shape was estimated by the elliptical Fourier analysis on the data from 11 natural and four common garden populations. Leaf morphology analyses indicate the morphological divergence does not show strong correlation with the genetic differentiation ( R  = 0.260, P  = 0.069). By comparing the 95% confidence interval of Q _ST with that of F _ST, Q _ST values for five out of 12 quantitative traits are significantly higher than the average F _ST value over eight microsatellite loci. The comparison of F _ST and Q _ST suggests that two kinds of traits can be driven by different evolutionary forces, and the population divergence in leaf morphology is shaped by local selections.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 505–516.     

Population genetics of a cyclostome species pair, river lamprey (Lampetra fluviatilis L.) and brook lamprey (Lampetra planeri Bloch)

Horizontal agarose gel electrophoresis of 24 allozyme loci in four species of Central European lampreys (321 Lampetra planeri , 83 L. fluviatilis , 11 Eudontomyzon mariae and nine Petromyzon marinus ) was used to study the 'paired species' L. fluviatilis and L. planeri . The genetic differentiation of the anadromous river lamprey ( L. fluviatilis ) from the stationary brook lamprey ( L. planeri ) was within the range of ingroup differentiation of the latter, but L. fluviatilis exhibited much greater population cohesion over a more extended geographic range: G _ST = 0.0537 versus G _ST = 0.3398, N _em = 4.402 versus N _em = 0.4856, mean genetic among-stock distances D = 0.0047 versus D = 0.0257. L. planeri populations coexisting geographically with L. fluviatilis in the Rhine and Elbe river systems were genetically more cohesive than L. planeri stocks from the Danubian basin where L. fluviatilis is absent. Danubian L. planeri populations exhibit a lower degree of heterozygosity than brook lampreys from the Rhine river system, but comprise deeper genetic lineages ( G _ST = 0.4629 versus G _ST = 0.2434), despite being sampled from a much more restricted area. Isolation-by-distance is observed for L. planeri from the Danubian but not from the Atlantic drainage basins. Transspecific gene flow between L. planeri from Atlantic drainage basins and the long-distant migrating L. fluviatilis is inferred, raising doubt on the validity of two separate biospecies. E. mariae and P. marinus are clearly differentiated from Lampetra spp. at several allozyme loci.     

PATTERNS OF GENETIC ARCHITECTURE FOR LIFE-HISTORY TRAITS AND MOLECULAR MARKERS IN A SUBDIVIDED SPECIES

Abstract Understanding the utility and limitations of molecular markers for predicting the evolutionary potential of natural populations is important for both evolutionary and conservation genetics. To address this issue, the distribution of genetic variation for quantitative traits and molecular markers is estimated within and among 14 permanent lake populations of Daphnia pulicaria representing two regional groups from Oregon. Estimates of population subdivision for molecular and quantitative traits are concordant, with Q _ST generally exceeding G _ST. There is no evidence that microsatellites loci are less informative about subdivision for quantitative traits than are allozyme loci. Character-specific comparison of Q _ST and G _ST support divergent selection pressures among populations for the majority of life-history traits in both coast and mountain regions. The level of within-population variation for molecular markers is uninformative as to the genetic variation maintained for quantitative traits. In D. pulicaria , regional differences in the frequency of sex may contribute to variation in the maintenance of expressed within-population quantitative-genetic variation without substantially impacting diversity at the genic level. These data are compared to an identical dataset for 17 populations of the temporary-pond species, D. pulex .     

Conservation Genetics of an Endangered Herb, Hanabusaya asiatica (Campanulaceae)

Abstract: Hanabusaya asiatica (Nakai) Nakai (Campanulaceae), a bee- pollinated, perennial herb, is restricted to the mountainous regions of the eastern-central Korean peninsula. Allozyme analyses for 348 individuals assessed the levels of genetic diversity for five populations. Spatial autocorrelation statistics were also used to examine the spatial distribution of allozyme polymorphisms. The species maintains high levels of allozyme diversity ( H _eS = 0.217) and it exhibits low allozyme differentiation among populations ( G _ST = 0.132) compared with other endemics (mean H _e = 0.096, G _ST = 0.248). There is an apparent pattern of isolation by distance among populations. These results suggest that H. asiatica is at a genetic equilibrium. A considerable deficit in numbers of heterozygotes suggests mating among relatives in populations. At least three populations of H. asiatica should be sampled or conserved to capture or maintain > 99 % of the genetic diversity in the species as a whole. Within local populations, individuals are distributed in a structured, isolation by distance, manner. Approximate genetic patch width in the populations of H. asiatica examined is 5 - 8 m. For conservation purposes, it is suggested that, in general, the sampling of H. asiatica should be conducted at intervals in order to efficiently sample the genetic diversity across an entire population.     

Small-Scale Fragmentation Effects on Local Genetic Diversity in Two Phyllostomid Bats with Different Dispersal Abilities in Panama

Habitat fragmentation is one of the greatest threats to biodiversity. Despite their importance for conservation, the genetic consequences of small-scale habitat fragmentation for bat populations are largely unknown. In this study, we linked genetic with ecological and demographic data to assess the effects of habitat fragmentation on two species of phyllostomid bats ( Uroderma bilobatum and Carollia perspicillata ) that differ in their dispersal abilities and demographic response to fragmentation. We hypothesized that population differentiation and the effect of habitat fragmentation on levels of genetic diversity will be a function of the species' mobility. We sequenced mtDNA from 232 bats caught on 11 islands in Gatún Lake, Panamá, isolated from the mainland for ca 90 yr, and in adjacent, continuous forest on the mainland. Populations of both species showed significant genetic differentiation ( F _ST). Consistent with our prediction, population subdivision was lower in the highly mobile U. bilobatum ( F _ST= 0.01) compared to the less vagile C. perspicillata ( F _ST= 0.06), and only the latter species showed a pattern indicative of isolation by distance and, in addition, an effect of fragmentation. Genetic erosion as a result of fragmentation was also only detectable in the less mobile species, C. perspicillata , where haplotype diversity was lower in island compared to mainland populations. Our results suggest that some Neotropical bat species are prone to loss of genetic variation in response to anthropogenic small-scale habitat fragmentation. In this context, our findings point toward mobility as a good predictor of a species' vulnerability to fragmentation and altered population genetic structure.     

Genetic diversity and genetic structure of populations of Ranunculus japonicus Thunb. (Ranunculaceae)

Abstract In order to clarify the genetic diversity and population structure of Ranunculus japonicus , allozymic analysis was conducted on 60 populations in southwestern Japan. Considerable genetic variati ons were detected among the populations of R. japonicus . The genetic diversities within species ( H _es = 0.215) and within populations ( H _ep = 0.172) were slightly higher than those of other perennial herbs with widespread distribution and outcrossing plants. Significantly higher values of fixation index were detected in some populations, which might have arisen from restricted mating partners. The majority of genetic variation (approx. 80%) resided within a population and a moderate level of genetic differentiation ( G _ST = 0.203) was observed among populations. The F _ST value (0.203) suggests the existence of a substantial population structure in this species. The highly significant correlation between geographic distance and F _ST values indicates that isolation by distance has played an important role in the construction of the genetic structure of this species.     

Population genetics and the conservation status of the threatened Iberian steppe grass Puccinellia pungens (Pau) Paunero (Poaceae)

Puccinellia pungens (Pau) Paunero is a narrowly endemic grass found in two continental saline lagoons of north-eastern Spain. This rare plant has been classified as 'at risk of extinction' in several national and European catalogues of endangered species. Recent demographic studies indicate that population sizes greatly exceed several million individuals, challenging that threat category. Our genetic analysis, based on allozymes, has shown that in spite of the large population sizes, very low levels of genetic variation were found in P. pungens . Genetic variation was similar in most populations, but the largest, Gallocanta lagoon as a whole, had less variation (35% polymorphic loci, 1.4 alleles/locus, H _T = 0.038) than the more restricted Royuela range (45% polymorphic loci, 1.5 alleles/locus, H _T = 0.056), suggesting a recent population expansion of the Gallocanta populations from few founder lines. The low genetic distances among populations also suggest a recent divergence. The low genetic variation observed cannot be explained fully by eventual clonal spread and rare seedling establishment in the hypersaline environment. This low variation seems to result from extreme recent population bottlenecks as a consequence of habitat conversion to agricultural fields. In the light of our data, it seems unlikely that reinforcement of populations could increase the genetic diversity of the populations. Hence, conservation efforts should focus on avoiding further habitat loss of this endangered steppe grass species.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 269–281.     

松嫩平原两种趋异类型羊草对干旱胁迫的生理响应

采用盆栽实验,对灰绿和黄绿两种趋异类型羊草（Leymus chinensis(Trin.)Tzvel.）幼苗期用聚乙二醇（PEG）胁迫进行干旱生理指标测定,结果表明,在干旱胁迫下,灰绿型羊草和黄绿型羊草的电解质外渗率、脯氨酸、植株含水率、植株鲜重、SO4^2-、NO3^-之间均有显著或极显著差异,灰绿型羊草叶片电解质外渗率和叶绿素含量的b值均大于黄绿型羊草,而植株含水率的b值则小于黄绿型羊草,灰绿型羊草脯氨酸含量均大于黄绿型羊草,因子分析表明,脯氨酸是两种趋异类型羊草干旱胁迫生理反应的主要因子,两种趋异类型羊草在生理响应中均体现出耐旱能力,但灰绿型羊草的耐旱能力比黄绿型更强,两种趋异类型羊草在耐旱生理上有明显分化。     

Microsatellite analysis of genetic population structure in an endangered salmonid: the coastal cutthroat trout (Oncorhynchus clarki clarki)

The genetic population structure of coastal cutthroat trout ( Oncorhynchus clarki clarki ) in Washington state was investigated by analysis of variation in allele frequencies at six highly polymorphic microsatellite loci for 13 anadromous populations, along with one outgroup population from the Yellowstone subspecies ( O. clarki bouvieri) (mean heterozygosity = 67%; average number of alleles per locus = 24). Tests for genetic differentiation revealed highly significant differences in genotypic frequencies for pairwise comparisons between all populations within geographical regions and overall population subdivision was substantial ( F _ST = 0.121, R _ST = 0.093), with 44.6% and 55.4% of the among-population diversity being attributable to differences between streams ( F _SR = 0.054) and between regions ( F _RT = 0.067), respectively. Analysis of genetic distances and geographical distances did not support a simple model of isolation by distance for these populations. With one exception, neighbour-joining dendrograms from the Cavalli-Sforza and Edwards' chord distances and maximum likelihood algorithms clustered populations by physiogeographic region, although overall bootstrap support was relatively low (53%). Our results suggest that coastal cutthroat trout populations are ultimately structured genetically at the level of individual streams. It appears that the dynamic balance between gene flow and genetic drift in the subspecies favours a high degree of genetic differentiation and population subdivision with the simultaneous maintenance of high heterozygosity levels within local populations. Results are discussed in terms of coastal cutthroat trout ecology along with implications for the designation of evolutionarily significant units pursuant to the US Endangered Species Act of 1973 and analogous conservation units.     

Marked genetic divergence revealed by allozymes among populations of the guppy Poecilia reticulata (Poeciliidae), in Trinidad

Populations of the guppy Poecilia reticulata from six locations in N. Trinidad were examined by starch gel electrophoresis to estimate their degree of genetic divergence. Variability at seven enzyme-coding loci demonstrated that populations differed markedly in allele frequencies with some allelic substitution between sites (for 23 loci, Nei's mean genetic identity, Ī ranged from 0.869–1.00; the coefficient of gene differentiation, G _ST= 0.086; and the absolute differentiation between populations, _m= 0.044). There was a good correspondence between degree of physical isolation and extent of genetic differentiation, as exemplified by the partitioning of gene diversity (Nei's gene diversity analysis = 66% between river basins; 32% within river basins; 2% within rivers), though there was considerable variability in the contribution of individual loci. Most populations were in Hardy-Weinberg equilibrium, and any significant deviations were due exclusively to heterozygote deficiencies. The patterns of population differentiation are discussed in relation to probable past geological and historical events, and present-day evolutionary forces. Notable among these are previous continental land connections, periodic immigration from N.E. South America, and post-colonization events including differential predation, sexual selection, apparent restricted vagility and small effective population sizes.     

Comparison of quantitative and molecular genetic variation of native vs. invasive populations of purple loosestrife (Lythrum salicaria L., Lythraceae)

Study of adaptive evolutionary changes in populations of invasive species can be advanced through the joint application of quantitative and population genetic methods. Using purple loosestrife as a model system, we investigated the relative roles of natural selection, genetic drift and gene flow in the invasive process by contrasting phenotypical and neutral genetic differentiation among native European and invasive North American populations ( Q _ST −  F _ST analysis). Our results indicate that invasive and native populations harbour comparable levels of amplified fragment length polymorphism variation, a pattern consistent with multiple independent introductions from a diverse European gene pool. However, it was observed that the genetic variation reduced during subsequent invasion, perhaps by founder effects and genetic drift. Comparison of genetically based quantitative trait differentiation ( Q _ST) with its expectation under neutrality ( F _ST) revealed no evidence of disruptive selection ( Q _ST >  F _ST) or stabilizing selection ( Q _ST <  F _ST). One exception was found for only one trait (the number of stems) showing significant sign of stabilizing selection across all populations. This suggests that there are difficulties in distinguishing the effects of nonadaptive population processes and natural selection. Multiple introductions of purple loosestrife may have created a genetic mixture from diverse source populations and increased population genetic diversity, but its link to the adaptive differentiation of invasive North American populations needs further research.     

Molecular and quantitative trait variation within and among populations of the intertidal copepod Tigriopus californicus

Abstract While molecular and quantitative trait variation may be theoretically correlated, empirical studies using both approaches frequently reveal discordant patterns, and these discrepancies can contribute to our understanding of evolutionary processes. Here, we assessed genetic variation in six populations of the copepod Tigriopus californicus. Molecular variation was estimated using five polymorphic microsatellite loci, and quantitative variation was measured using 22-life history and morphometric characters. Within populations, no correlation was found between the levels of molecular variation (heterozygosity) and quantitative variation (heritability). Between populations, quantitative subdivision ( Q _ST) was correlated with molecular subdivision when measured as F _ST but not when measured as R _ST. Unlike most taxa studied to date, the overall level of molecular subdivision exceeded the level of quantitative subdivision ( F _ST= 0.80, R_ST = 0.89, Q _ST = 0.30). Factors that could contribute to this pattern include stabilizing or fluctuating selection on quantitative traits or accelerated rates of molecular evolution.     

Population genetic structure in Myrtus communis L. in a chronically fragmented landscape in the Mediterranean: can gene flow counteract habitat perturbation?

Ancient managed landscapes provide ideal opportunities to assess the consequences of habitat fragmentation on the patterns of genetic diversity and gene flow in long-lived plant species. Using amplified fragment length polymorphism (AFLP) and allozyme markers, we quantified seed-mediated gene flow and population genetic diversity and structure in 14 populations of Myrtus communis (myrtle), a common endozoochorous shrub species of forest patches in lowland agricultural Mediterranean areas. Overall, allozyme diversity for myrtle was low (P₉₅   =   25%; A   =   1.411; H_e = 0.085) compared to other known populations, and a significant portion of populations (57%) had lower levels of allelic diversity and/or heterozygosity than expected at random, as shown by simulated resampling of the whole diversity of the landscape. We found significant correlations between allozyme variability and population size and patch isolation, but no significant inbreeding in any population. Genetic differentiation among populations for both allozyme and AFLP markers was significant (Φ_ST = 0.144 and Φ_ST = 0.142, respectively) but an isolation-by-distance pattern was not detected. Assignment tests on AFLP data indicated a high immigration rate in the populations ( ca. 20–22%), likely through effective seed dispersal across the landscape by birds and mammals. Our results suggest that genetic isolation is not the automatic outcome of habitat destruction since substantial levels of seed-mediated gene flow are currently detectable. However, even moderate rates of gene flow seem insufficient in this long-lived species to counteract the genetic erosion and differentiation imposed by chronic habitat destruction.     

Population genetic structure of the butterfly Melitaea didyma (Nymphalidae) along a northern distribution range border

The population genetic structure of the butterfly Melitaea didyma was studied along the northern distribution range border in Central Germany by means of allozyme electrophoresis. Individuals were sampled from a total of 21 habitat patches from four regions, and two provinces. Sampling was designed to estimate local vs. regional differentiation. High levels of variability were found, H _e= 0.14–0.21. The mean expected sample heterozygosity from one region, Mosel, was significantly lower than from the Hammelburg region, H _e= 0.17 and 0.19, respectively. Two hierarchical levels of genetic differentiation were found. Within regions individuals sampled from different patches behaved as belonging to one population with high levels of gene flow (Hammelburg F _ST= 0.015, Mosel F _ST= 0.044), though local isolation barriers did create a substructuring of these populations. The inbreeding coefficients, F _IS, were constant over all sample levels, suggesting a similar distribution of habitat patches within regions. Between regions gene flow was limited. An isolation by distance analysis indicated that the hierarchical structure, at the provincial level, may be breaking down due to isolation of regional populations. A more general observation was that the sampling design may greatly have influenced the estimation of genetic differentiation. Depending on which samples were included, overall F _ST estimates ranged from 0.059–0.090.     

Population genetic structure of wild rice Oryza glumaepatula distributed in the Amazon flood area influenced by its life-history traits

Wild plant species develop their own way of living to adapt to the specific environment of their habitats. Their life-history traits strongly affect the genetic structure of the population. The wild species Oryza glumaepatula Steud. growing in the Amazon basin seems to have characteristic life-history traits suited for the flood condition. At the vegetative growth stage, the culms frequently break at internodes. With no roots anchoring on the ground, plant bodies floating in the water move downriver by water current and wind. To examine the association between the life-history traits and genetic population structure of Amazonian O. glumaepatula , we analysed allozyme variability at 29 loci of 16 enzymes using 37 populations from five regions. Allozymes were not so variable (total gene diversity H _E = 0.044) compared with Asian wild rice, O. rufipogon Griff. The bottleneck effect and rare opportunity of interspecies gene flow may prevent the development of allozyme variability. Population genotypes tended to be differentiated among geographically isolated regions. Observed heterozygosities were much lower than expected heterozygosities, or gene diversity ( H _O = 0.003 for whole population) and F _IS over polymorphic loci was 0.931, indicating that O. glumaepatula has developed an inbreeding system. But, the intrapopulation gene diversity ( H _S) was higher than interpopulation gene diversity ( D _ST), as generally observed in outbreeding populations. The migration ability of O. glumaepatula makes long-distance seed dispersal possible. This might have led to frequent gene flow among populations.