Genetic variation and population structure in Korean populations of sand dune speciesSalsola komarovi (Chenopodiaceae)

Salsola komarovi lljin is a herbaceous annual native to the sand dunes and beaches of Japan, northern China, Sakhalln and Korea. Starch-gel electrophoresis was conducted on leaves and stems collected from 300 plants in eight Korean populations. The mean number of alleles per locus (A _p=1.51), mean expected heterozygosity (He _p=0.116), and total genetic diversity (H _T=0.279) were comparable with those for species with similar life history and ecological traits. A general conformance of genotype frequencies to Hardy-Weinberg expectations (meanF _IS=−0.030) indicates thatS. komarovi is an outcrossing species. Slightly more than 20% of the genetic variation was found among populations (F _ST=0.204). In addition, significant differences in allele frequency were detected between populations at all 11 polymorphic loci (P<0.001). Nei's genetic identities range from 0.885 to 0.985 with a mean of 0.942. However, indirect estimates of the number of migrant per generation (0.97, calculated fromF _ST and 0.31, calculated from seven private alleles) indicate that the levels of gene flow is low among Korean populations. Although the species maintains a moderate level of genetic variation within populations, the small, isolated natural populations of the species have been severely destructed by human activities, particularly in summer season. If this is true, conservation efforts should be focused on those populations that currently maintain the most genetic diversity (e.g., populations of Cheju Island and coast of the southwestern Korean Peninsula).     

Genetic structure of age classes in Camellia japonica (Theaceae)

Camellia japonica L. (Theaceae), an insect- and bird-pollinated, broad-leaved evergreen tree, is widely distributed in Japan and the southern Korean peninsula. The species has a relatively even age distribution within populations, which may influence the spatial genetic structure of different age classes relative to species with typical L-shaped age distributions. To determine whether the internal spatial genetic structure found in seedlings and young individuals carries over into adults, we used allozyme loci, F-statistics, spatial autocorrelation statistics (Moran's I), and coancestry measures to examine changes in genetic structure among seven age classes in a population (60-m x 100-m area) in southern Korea. In seedlings, weak but significant positive values of Moran's I-statistics and coancestry measures were found for distances less than 14 m, which is consistent with a mechanism of limited seed dispersal combined with overlapping seed shadows. This spatial structure, however, dissipates in older age classes, and in adults genetic variation has an essentially random spatial distribution. Morisita's index of dispersion of individuals in each age class showed that seedlings and juveniles are more highly clustered than are older individuals. These results suggest that self-thinning changes the spatial relationships of individuals, and thus genotypes. A multilocus estimate of FST (0.008) shows a small but statistically significant difference in allele frequencies among age classes. In summary, intrapopulation genetic structure within and among age classes of C. japonica was significant but weak. Despite presumably limited seed dispersal, weak spatial genetic structure in juveniles suggests overlapping seed shadows followed by self-thinning during recruitment. The present study also demonstrates that studies of spatial genetic structure focusing on limited numbers of generations may not be sufficient to reveal the entire picture of genetic structure in populations with overlapping generations.     

Genetic variation and population structure in Scandinavian wolverine (Gulo gulo) populations

Wolverine (Gulo gulo) numbers in Scandinavia were significantly reduced during the early part of the century as a result of predator removal programmes and hunting. Protective legislation in both Sweden and Norway in the 1960s and 1970s has now resulted in increased wolverine densities in Scandinavia. We report here the development of 15 polymorphic microsatellite markers in wolverine and their use to examine the population sub-structure and genetic variability in free-ranging Scandinavian wolverine populations as well as in a sample of individuals collected before 1970. Significant subdivision between extant populations was discovered, in particular for the small and isolated population of southern Norway, which represents a recent recolonization. Overall genetic variability was found to be lower than previously reported for other mustelids, with only two to five alleles per locus and observed heterozygosities (H(O)) ranging from 0.269 to 0.376 across the examined populations, being lowest in southern Norway. Analysis of the mitochondrial DNA control region revealed no variation throughout the surveyed populations. As the historical sample did not show higher levels of genetic variability, our results are consistent with a reduction in the genetic variation in Scandinavian wolverines that pre-dates the demographic bottleneck observed during the last century. The observed subdivision between populations calls for management caution when issuing harvest quotas, especially for the geographically isolated south Norwegian population.     

Genetic variation and population structure in Korean endemic species: IV.Hemerocallis hakuunensis (Liliaceae)

Hemerocallis hakuunensis, a Korean endemic species, maintains considerably higher levels of allozyme variation within populations (meanHe=0.253) and substantially lower levels of allozyme divergence among populations (meanG _ST=0.077) than average values reported for other insect-pollinated, outcrossing herbs. Indirect estimates of the number of migrants per generation (Nm=3.00, calculated fromG _ST;Nm=3.57, calculated from the frequency of nine alleles unique to single populations) indicate that gene flow has been extensive inH. hakuunensis. This is somewhat surprising when we consider the fact that no specialized seed dispersal mechanism is known, flowers are visited by bees, and the present-day populations of the species are discontinous and isolated. Results of a spatial autocorrelation analysis based on mean allele frequencies of 19 populations reveal that only 13% (95/720 cases) of Moran'sI values for the ten interpopulational distance classes are significantly different from the expected values and no distinct trend with respect to the distance classes is detected. Although it is unclear how the populations are genetically homogenous, it is highly probable thatH. hakuunensis might have a history of relatively large, continuous populations that had more chance for gene movement among adjacent populations after the last Ice Age. In addition, occasional hybridization withH. thunbergii in areas of sympatry in the central and southwestern Korean Peninsula may be one factor contributing the present-day high allozyme variation observed inH. hakuunensis.     

Genetic variation and population structure in Korean endemic species: III.Hosta minor (Liliaceae)

Hosta minor, an insect-pollinated and rhizomatous herbaceous perennial, occurs in eastern and southern Korean Peninsula. AlthoughH. minor is a Korean endemic species and most populations of the species are scattered, the species maintains considerably high levels of genetic variation within the species, with a moderate level of variation (14%) found among populations. Nineteen of the 29 putative loci resolved (66%) were polymorphic within the species, the mean number of alleles per locus was 2.10 across all populations and averaged 1.68 within populations. In addition, genetic diversity was a considerably higher (for species and population level, mean estimates of genetic diversity were 0.275 and 0.230, respectively) than the average for other long-lived herbaceous perennials. Indirect estimate of the number of migrants per generation (Nm=1.03, calculated from mean G_ST) was moderate. Factors contributing to the high levels of genetic diversity found within populations ofH. minor include population maintenance via sexual and asexual modes of reproduction, primarily outcrossing breeding system, long generation time, probable ancient polyploid origin of the species, and moderate levels of seed dispersal by wind. Human disturbance in South Korea such as road and apartment constructions appears to be the major threat to this genetically diverse species.     

Floral anatomy ofCamellia japonica (Theaceae)

The floral anatomy ofCamellia japonica is described and the origin of its multistaminate androecium is considered. Of significance is the observation that the complex polyandry of the genus overlies a basic vascular obdiplostemonous pattern. This is evidenced by two systems of staminal bundles. The first diverges from a set of five common petal-stamen bundles and subsequently divides further. The second set of five staminal trunk bundles emerges from the central cylinder slightly above the petal-stamen bundles which are antepetalous. The observations will aid phylogenetic reconstruction for members of the polyphyletic order Dilleniidae to whichCamellia belongs, and in which the polyandry has been too simply and sometimes incorrectly interpreted as a primitive condition.     

Genetic variation and population structure in central and isolated populations of balsam fir, Abies balsamea (Pinaceae)

Genetic variation and spatial genetic structure in balsam fir (Abies balsamea) were examined in two isolated populations in Iowa and Minnesota thought to be paleorefugia and in two ecologically central populations in old-growth forests of Upper Michigan. Overall levels of genetic variability at 22 allozyme loci were lower than that found in most conifer species (H(o) values ranged from 0.005 in the isolated populations to 0.025 in the central populations). The mean F(IS) value (0.154) was larger than usually found in conifers and suggests moderate levels of inbreeding. The mean F(ST), an estimate of genetic diversity among populations, was 3.7% of the total diversity, a value lower than the mean for conifers. Nm, the number of migrants per generation, was 6.5, suggesting either some gene flow among populations or a lack of genetic differentiation. Spatial autocorrelation analysis revealed a moderately patchy structure, with gene flow distances of 30-70 m in the central populations and at least 10 m in the isolated populations. The future of the ecologically central populations depends on maintenance of an intact forest mosaic. The low genetic variability in the small, isolated populations suggests that habitat fragmentation has led to a reduction in evolutionary potential and that the future viability of these populations will likely require active management in the face of global climate change.     

Genetic variation and population structure ofCarex breviculmis (Cyperaceae) in Korea

We determined the genetic diversity and population structures ofCarex breviculmis (Cyperaceae) populations in Korea, using genetic variations at 23 allozyme loci.C. breviculmis is a long-lived herbaceous species that is widely distributed in eastern Asia. A high level of genetic variation was found in 15 populations. Twelve enzymes revealed 23 loci, of which 11 were polymorphic (47.8%). Genetic diversity at the speciesand population levels were 0.174 and 0.146, respectively. Total genetic diversity (H_T = 0.363) and within-population genetic diversity (H_s = 0.346) were high, whereas the extent of the population divergence was relatively low (G_ST = 0.063). Deviation from random mating (Fis) within the 15 populations was 0.206. An indirect estimate of the number of migrants per generation(Nm = 3.69) indicated that gene flow was extensive among Korean populations of this species. Analysis of fixation indices revealed a substantial heterozygote deficiency in some populations and at some loci. Genetic identity between popu-lations was high, exceeding 0.956.     

Genetic variation and structure of fisher (Martes pennanti) populations across North America

Fishers are mid-sized forest carnivores indigenous to North America that experienced sharp population declines from the early 1800s through to the mid-1900s. To evaluate levels of genetic variation within and subdivision among northern fisher populations 459 individuals were genotyped using 13 microsatellite loci. Genetic diversity was found to be slightly lower in re-introduced populations than in adjacent indigenous populations. Furthermore, fisher populations revealed much more genetic structuring than two closely related mustelids. Further investigation is needed to determine if fishers are more philopatric than martens and wolverines or if barriers to dispersal explain the levels of structure identified in this study.     

天然片断生境中山姜(Alpinia japonica)种群遗传结构

理论和实验研究表明片断化是导致生物多样性丧失的主要因素之一,但有关研究基本上集中在人类活动引发的片断化生境体系中.由于长期气候变化以及地形等因素的影响,一些物种的种群之间天然情况下就存在隔离,对这些种群进行研究可以弥补人类活动引起的片断化体系经历时间较短的不足.山姜是一个喜湿耐荫的多年生植物,分布在热带亚热带地区,由于气候和地形原因,该物种在浙江东部呈现天然片断化状态,如在浙江天童森林公园及其周边地区,仅分布在少数几个沟谷中.以这些种群为对象,采用RAPD标记分析经历长期天然片断化山姜种群遗传多样性程度和遗传分化格局.7条RAPD引物获得了69个位点,其中多态位点68个.种群水平遗传多样性较高,多态位点百分比、期望杂合度和Shannon多样性指数分别为78.81%～85.51%、0.3170～0.3430、0.4560～0.4914,这与其异交的繁殖方式有关,同时与山姜克隆生长,每个世代维持的时间长,种群更新降低也有关系.遗传变异大多分配在种群内,但种群间遗传分化达到显著程度,ΦST为0.297,计算的基因流中等,为0.592,不足以克服长期遗传漂变导致的种群分化,Mantel检验表明遗传距离与空间距离不存在相关关系,显示了长期片断化状态下遗传漂变的作用.     

Genetic variation and population structure in native Americans

We examined genetic diversity and population structure in the American landmass using 678 autosomal microsatellite markers genotyped in 422 individuals representing 24 Native American populations sampled from North, Central, and South America. These data were analyzed jointly with similar data available in 54 other indigenous populations worldwide, including an additional five Native American groups. The Native American populations have lower genetic diversity and greater differentiation than populations from other continental regions. We observe gradients both of decreasing genetic diversity as a function of geographic distance from the Bering Strait and of decreasing genetic similarity to Siberians--signals of the southward dispersal of human populations from the northwestern tip of the Americas. We also observe evidence of: (1) a higher level of diversity and lower level of population structure in western South America compared to eastern South America, (2) a relative lack of differentiation between Mesoamerican and Andean populations, (3) a scenario in which coastal routes were easier for migrating peoples to traverse in comparison with inland routes, and (4) a partial agreement on a local scale between genetic similarity and the linguistic classification of populations. These findings offer new insights into the process of population dispersal and differentiation during the peopling of the Americas.     

Genetic and clonal diversity in Korean populations ofVitex rotundifolia (Verbenaceae)

Vitex rotundifolia L.f. is a woody perennial and has sexual and asexual modes of reproduction. Allozyme study was conducted on 550 plants in 13 Korean populations. The levels of genetic variability and divergence within and among populations, respectively, are considerably lower and higher than the mean values for woody plants with similar life history tralts. Mean percentage of polymorphic loci (P _P), mean number of alleles per locus (A _P), and mean genetic diversity (He _P) within populations ofV. rotundifolia were: 16.7%, 1.21, and 0.047. On average, about 79% of the total variation inV. rotundifolia was common to all populations (meanG _ST=0.208). In addition, significant differences in allele frequencies among populations were found in all polymorphic loci examined (P<0.001). On the other hand, levels of genotypic diversity within and among populations were moderate. About 44% (18/41) of multilocus genotypes were “local genotypes” (genotypes occurring in only one population), whereas only one “widespread genotype” (genotypes occurring in more than 75% of the populations) were detected. The mean number of multilocus genotypes per population (G) and mean genotypic diversity index (D _G) were 8.4 and 0.74, respectively. Most common multilocus genotypes found in populations were homozygous for five polymorphic loci. The abundance of ramets of these genets is responsible for the low levels of expected heterozygosity within populations. The results indicate that clonal reproduction may act as an enhancer of genetic drift by reducing effective size of local populations ofV. rotundifolia.     

Genetic variation and population structure in remnant populations of black rhinoceros, Diceros bicornis, in Africa

Black rhinoceros (Diceros bicornis) are one of the most endangered mammal species in Africa, with a population decline of more than 96% by the end of the last century. Habitat destruction and encroachment has resulted in fragmentation of the remaining populations. To assist in conservation management, baseline information is provided here on relative genetic diversity and population differentiation among the four remaining recognized subspecies. Using microsatellite data from nine loci and 121 black rhinoceros individuals, and comparing the results with those of other African species affected in similar ways, Diceros bicornis michaeli retained the most genetic diversity (heterozygosity 0.675) compared with Diceros bicornis minor (0.459) and Diceros bicornis bicornis (0.505), suggesting that the duration of the known bottlenecks in these populations has only had a limited impact on diversity. Comparable and moderate degrees of population differentiation were found between D. b. minor, D. b. bicornis and D. b. michaeli. Results from the single sample available of the most endangered subspecies, Diceros bicornis longipes, showed the least diversity of all individuals examined. This information should assist conservation management decisions, especially those affecting population viability assessments and selection of individuals for translocations, and will also facilitate subspecies identification for ex situ individuals of uncertain origin.     

Genetic variation in a population of the wild quail Coturnix coturnix japonica

To investigate genetic variation and to compare it with those of domestic quail populations, enzymatic and non-enzymatic proteins in a wild quail population were examined electrophoretically.
The wild quail population had a genetic variability considerably lower than those of domestic populations. The average heterozygosity estimated for 22 loci was 0.090 in the wild quail population.     

Genetic variation and population structure of two species of neo-tropical mud-mussels (Mytella spp)

Mytella guyanensis Lamarck (1819) and Mytella charruana d'Orbigny (1846) are widespread euryhaline bivalves that have become commercially important in Brazil. Despite their importance, however, no genetic information that would be useful to orient governmental policies is available for these species. We analyzed, through allozyme electrophoresis, populations of M. guyanensis and M. charruana along 3,500 km of Brazilian coast. Pairwise comparisons among gene frequencies in M. guyanensis resulted in high levels of pairwise gene identity (I = 0.976 to 0.998). Conversely, significant levels of population structure were found in both M. guyanensis (FST = 0.089) and M. charruana (FST = 0.102). Heterozygosity levels for both species were high (H(e) = 0.090 to 0.134 in M. guyanensis and H(e) = 0.191 to 0.228 in M. charruana). The larger population size of M. charruana could explain, at least partially, the higher levels of genetic variability for this species. These levels of genetic variability yield an effective population size estimate of about 300,000 for M. guyanensis, and 540,000 for M. charruana, based on neutralist expectations. Remarkably, these numbers are much smaller than the estimated actual population sizes. This distortion might be explained by unstable population sizes and it suggests that long-term genetic variability studies are crucial to prevent artifactual viability analysis data for these commercially exploited species.     

Genetic population structure, fitness variation and the importance of population history in remnant populations of the endangered plant Silene chlorantha (Willd.) Ehrh. (Caryophyllaceae)

Habitat fragmentation can lead to a decline of genetic diversity, a potential risk for the survival of natural populations. Fragmented populations can become highly differentiated due to reduced gene flow and genetic drift. A decline in number of individuals can result in lower reproductive fitness due to inbreeding effects. We investigated genetic variation within and between 11 populations of the rare and endangered plant Silene chlorantha in northeastern Germany to support conservation strategies. Genetic diversity was evaluated using AFLP techniques and the results were correlated to fitness traits. Fitness evaluation in nature and in a common garden approach was conducted. Our analysis revealed population differentiation was high and within population genetic diversity was intermediate. A clear population structure was supported by a Bayesian approach, AMOVA and neighbour-joining analysis. No correlation between genetic and geographic distance was found. Our results indicate that patterns of population differentiation were mainly caused by temporal and/or spatial isolation and genetic drift. The fitness evaluation revealed that pollinator limitation and habitat quality seem, at present, to be more important to reproductive fitness than genetic diversity by itself. Populations of S. chlorantha with low genetic diversity have the potential to increase in individual number if habitat conditions improve. This was detected in a single large population in the investigation area, which was formerly affected by bottleneck effects.     

Genetic variation and population structure of interleukin genes among seven ethnic populations from Karnataka,India

The extent of genetic variation and the degree of genetic differentiation among seven ethnic populations from Karnataka, India (Bunt, Havyak, Iyengar, Lingayath, Smartha, Vaishya, Vokkaliga), was investigated using four single nucleotide polymorphisms (SNPs: IL-1A 4845, IL-1B 3954, IL-1B 511 and IL-1RA 2018) of the interleukin gene cluster. Allele frequencies varied by threefold among these populations, which also differed for gene diversity and heterozygosity levels. The average degree of population subdivision among these castes was low (F _ST = 0.02). However, pair-wise interpopulation differentiation ranged from 0–7%, indicating no detectable differentiation to moderate differentiation between specific populations. The results of phylogenetic analysis based on genetic distances between populations agreed with known social and cultural data on these ethnic groups. Variation in the allele frequencies, as well as differentiation, may be attributed to differential selection and demographic factors including consanguinity among the ethnic groups. Information on the distribution of functionally relevant polymorphisms among ethnic populations may be important towards developing community medicine and public health policies.     

Genetic population structure of Littorina brevicula around Korean waters

Originally described from Spitzbergen, Greenland, Iceland and Scandinavia, Chaetozone setosa is now widely recognised to be a species complex by workers involved in analysing survey material in the northeast Atlantic. Chaetozone species were examined from wide-scale surveys of the Faroe-Shetland Channel and nearby areas, which included water depths ranging from 100 to 2000 m and diverse hydrographic conditions. Comparisons were made with other deep-water material from around Iceland. There appear to be at least five Chaetozone species occurring in the cold, deeper waters of the area. One of the commonest of these, from the lower West Shetland Continental Slope (Faroe-Shetland Channel) and the Iceland-Faroe Rise, is described as a new species.