Mean Allelic Richness Research Articles

Microsatellite variability reveals high genetic diversity and low genetic differentiation in a critical giant panda population

Abstract Understanding present patterns of genetic diversity is critical in order to design effective conservation and management strategies for endangered species. Tangjiahe Nature Reserve (NR) is one of the most important national reserves for giant pandas Ailuropoda melanoleuca in China. Previous studies have shown that giant pandas in Tangjiahe NR may be threatened by population decline and fragmentation. Here we used 10 microsatellite DNA markers to assess the genetic variability in the Tangjiahe population. The results indicate a low level of genetic differentiation between the Hongshihe and Motianling subpopulations in the reserve. Assignment tests using the Bayesian clustering method in STRUCTURE identified one genetic cluster from 42 individuals of the two subpopulations. All individuals from the same subpopulation were assigned to one cluster. This indicates high gene flow between subpopulations. F statistic analyses revealed a low FIS-value of 0.024 in the total population and implies a randomly mating population in Tangjiahe NR. Additionally, our data show a high level of genetic diversity for the Tangjiahe population. Mean allele number (A), Allelic richness (AR) and mean expected heterozygosity (HE) for the Tangjiahe population was 5.9, 5.173 and 0.703, respectively. This wild giant panda population can be restored through concerted effort.

Development of novel microsatellite markers for the invasive Northern Pacific seastar, Asterias amurensis

The Northern Pacific seastar, Asterias amurensis, is a benthic marine predator, which has recently established several invasive populations in Australian waters. To investigate population structure, diversity and patterns of connectivity, we isolated and characterised 27 microsatellite loci and tested their polymorphism based on 46 individuals from two invasive populations. The mean allelic richness was 4.33; observed heterozygosity was 0.42, while the percentage of polymorphic loci was 92.6%. The polymorphic markers will prove useful in the assessment of population genetic parameters, in both invasive and native A. amurensis populations.

Genetic variability and individual assignment of Chinese indigenous sheep populations (Ovis aries) using microsatellites

The purpose of this study was to assess the genetic characteristics of six breeds of Chinese local sheep using 19 microsatellite loci and to effectively validate statistical methods for individual assignment based on informative microsatellites. All the six breeds deviated from Hardy-Weinberg equilibrium expectations, while the majority of markers complied. The polymorphism information content (PIC) of overall loci for the six populations ranged from 0.283 (SRCRSP5) to 0.852 (OarVH72). Tibetan sheep were the most diverse population with the highest mean allelic richness (6.895), while Ujmuqin (UQ) harboured the lowest allelic richness (6.000). The F-statistics for the six populations were F(IS) = -0.172, F(IT) = -0.082 and F(ST) = 0.077, respectively. Furthermore, the pair-wise F(IS) revealed a moderate genetic differentiation among populations (P < 0.01), indicating that all breeds can be considered genetically independent entities. The lowest genetic differentiation was between Tengchong (TC) and UQ (F(ST) = 0.041), and the highest one was between TC and Fat-tailed Han (F(ST) = 0.111). In comparing the three statistical models, we note that the seven microsatellite loci (MAF65, OarJMP58, SRCRSP9, MCM140, OarAE129, BM8125 and SRCRSP5) commonly used for individual assignment will ensure a powerful detection of individual origin, with accuracy up to 91.87%, when the likelihood-based method is used. Overall, these findings shed light onto the genetic characteristics of Chinese indigenous sheep and offer a set of microsatellite loci that is simple, economic and highly informative for individual assignment of Chinese sheep.

Genetic diversity and geographical peculiarity of Tibetan wild soybean (Glycine soja)

Tibet is the highest Plateau in China and the world, however wild soybean has been found in its southeastern fringe region adjacent to the northwest of Yunnan Province. Tibetan wild soybean was distributed only in the Gongrigabuqu-River Gorge in southeast Tibet. This regional plant species belong to the flora of Himalayan-Hengduan Mountains, which comprises composite elements of ancient arcto-tertiary flora, tropical and semitropical flora. To date, few studies have been carried out on Tibetan wild soybean. Studying Tibetan wild soybean together with other regional ones helps to understand the history of the origin and dissemination of wild soybean species in China. Here we reported the status of genetic diversity in Tibetan wild soybean and the genetic relationship between Tibetan and other regional wild soybeans revealed by nuclear SSR markers. The results showed that the Tibetan wild soybean sample was significantly differentiated from other regional ones, as characterized by the lowest mean allelic richness (\( {\hat{\text{r}}} \) = 1.40) and gene diversity (He = 0.130) and the highest ratios of regionally unique alleles (63.26%) and fixed alleles (46.94%). These genetic attributes suggested that Tibetan wild soybean may have undergone severe adaptation selection for the plateau climate and ecogeographical conditions, and had less genetic exchange with inland populations. The regional population south of the Changjiang River (Central and South China) showed higher genetic richness. UPGMA cluster analysis revealed two large geographical groups, Tibetan and inland, and revealed closer relationship among the eastern populations, which suggested that the dissemination of this species in the eastern part of China might be rapider.

Short Communication Isolation and characterization of microsatellite markers for the White Cloud Mountain minnow (Tanichthys albonubes) in wild and cultured populations

We developed 12 microsatellite loci for the endangered minnow species, Tanichthys albonubes, using PCR-based isolation of microsatellite arrays. These new markers were tested in 26 individuals from a wild population collected from Guangzhou in China and 26 individuals from a cultured strain. The number of alleles ranged from two to nine and the expected heterozygosity from 0.177 to 0.853. The wild population had significantly higher allelic richness than the cultured strain, with a mean allelic richness of 5.52 (range = 3.69-8.64) and 3.13 (range = 1.99-5.73) for the wild population and the cultured strain, respectively. No evidence of a recent bottleneck was detected in the wild population, but it was found in the cultured strain based on the BOTTLENECK test. These primers can be used to understand the demography and to examine genetic differences between the cultured T. albonubes strains and wild populations to help determine conservation and reintroduction strategies.

Isolation and characterization of 15 microsatellite loci in the stingless bee Plebeia remota (Apidae: Meliponini)

The destruction of Brazilian natural habitats has reduced bee populations and negative impacts of native flora pollination have been noticed. This work describes the isolation and characterization of microsatellite loci and evaluates them as molecular markers to study genetic variability of the stingless bee Plebeia remota. A microsatellite enriched genomic library was constructed and 15 primer pairs were designed for this species. The survey was conducted by analyzing 21 unrelated individuals. Genetic diversity indexes were calculated. The mean allelic richness was 6.3, the observed heterozygosity was 0.568, and the percentage of polymorphic loci was 93.33%. Also the primers were tested in cross-species amplification and showed promising results for P. droryana, P. emerina, P. lucii, P. meridionalis, P. pugnax, and P. saiqui. The microsatellite loci described here will be useful to evaluate genetic variability of stingless bees, and certainly will improve our knowledge about population dynamics especially in threatened environments.

New Microsatellite Markers for Examining Genetic Variation in Peripheral and Core Populations of the Coastal Giant Salamander (Dicamptodon tenebrosus)

The Coastal Giant Salamander (Dicamptodon tenebrosus) is classified as threatened at the northern periphery of its range in British Columbia (BC), Canada, primarily due to forestry practices and habitat fragmentation. Characterising dispersal behaviour and population connectivity is therefore a priority for this region, while genetic differentiation in core versus peripheral locations remains unstudied in this wide-ranging species. We present seven new polymorphic microsatellite markers for use in population genetic analyses of D. tenebrosus. We examine locus characteristics and genetic variation in 12 streams at the species' northern range limit in BC, and within two regions representing sub-peripheral (North Cascades) and core localities (South Cascades) in Washington State, United States. In BC, the number of alleles per locus ranged from 2–5 and observed heterozygosity ranged from 0.044–0.825. Genetic differentiation was highest between BC and the South Cascades, and intermediate between BC and the North Cascades. Across loci, mean allelic richness was similar across regions, while private allelic richness was highest in the core locality (corrected for sample size). These new microsatellite loci will be a valuable addition to existing markers for detailed landscape and population genetic analyses of D. tenebrosus across its range.

From glacial refugia to modern populations: new assemblages of organelle genomes generated by differential cytoplasmic gene flow in transcontinental black spruce

Assessing species' range-wide cytoplasmic diversity provides valuable insights regarding their dispersal and adaptive potential in a changing environment. Transcontinental chloroplast (cpDNA) and mitochondrial DNA (mtDNA) population structures were compared to identify putative ancestral and new cytoplasmic genome assemblages in black spruce (Picea mariana), a North American boreal conifer. Mean within-population diversity and allelic richness for cpSSR markers were 0.80 and 4.21, respectively, and diminished westward. Population differentiation based on G(ST) was lower for cpDNA than for mtDNA (G(ST) =0.104 and 0.645, respectively) but appeared comparable when estimated using Jost differentiation index (D=0.459 and 0.537, respectively). Further analyses resulted in the delineation of at least three genetically distinct cpDNA lineages partially congruent with those inferred from mtDNA data, which roughly corresponded to western, central and eastern Canada. Additionally, the patterns of variation in Alaska for both cpDNA and mtDNA markers suggested that black spruce survived the last glacial maximum in this northern region. The range-wide comparison of the geographic extent of cytoplasmic DNA lineages revealed that extensive pollen gene flow between ancestral lineages occurred preferentially from west to east during the postglacial expansion of the species, while seed-mediated gene flow remained geographically restricted. This differential gene flow promoted intraspecific cytoplasmic capture that generated new assemblages of cpDNA and mtDNA genomes during the Holocene. Hence, black spruce postglacial colonization unexpectedly resulted in an increase in genetic diversity with possible adaptive consequences.

High genetic diversity and possible evidence of a recent bottleneck in Adriatic bottlenose dolphins ( Tursiops truncatus)

The bottlenose dolphin ( Tursiops truncatus) is the only resident marine mammal species in the Croatian part of the Adriatic Sea, with an estimated number at around 220 individuals. It is an endangered and legally protected species in Croatia, and its demographic history is poorly known. This study investigates the level of genetic diversity in the bottlenose dolphin population from the Croatian part of the Adriatic Sea and a possibility of recent population size contraction, since there are indications that there has been intensive eradication operations in the mid 20th century that might have caused reductions in the effective population size and might have resulted in a loss of genetic variation. Thirty samples were genotyped at 12 dinucleotide microsatellite loci. The mean allelic richness (6.835 ± 0.705) and mean expected heterozygosity (0.692 ± 0.05) revealed high level of genetic diversity. Bottleneck analysis gave ambiguous evidence for a recent population decline in the investigated bottlenose dolphin population. The M ratio test, with two sets of parameter values, suggested a recent bottleneck; whereas the analysis by the Bottleneck program under three mutation models (TPM, SMM and IAM) showed no evidence for a genetic bottleneck. We take a more conservative approach to the interpretation of these results by accepting the evidence of a recent bottleneck. We suggest maintaining the current level of bottlenose dolphin protection in the area and careful monitoring of the population in the future.

Isolation and characterization of twenty polymorphic microsatellite markers for the endangered Dupont′s lark (Chersophilus duponti) and cross-amplification in crested lark (Galerida cristata) and thekla lark (Galerida theklae)

We developed twenty microsatellite markers for the Dupont′s lark (Chersophilus duponti), one of the most endangered European bird species, and tested in two related, more widely distributed species: crested lark (Galerida cristata) and thekla lark (Galerida theklae). 14 markers amplified and were polymorphic in Dupont′s lark, 11 in crested lark and 6 in thekla lark. Microsatellite variability analyses were carried out on Dupont′s lark (N = 23–28 individuals), crested lark (N = 9–10) and thekla lark (N = 14) populations in NE Spain showing moderate/high diversity, ranging from 1 to 13 alleles per locus. The mean allelic richness in Dupont’s lark was 6.21 and expected and observed heterozygosities ranged from 0.195 to 0.848 and from 0.071 to 0.889, respectively. Crested and thekla larks showed moderate/high diversity with a mean allelic richness of 4.36 and 4.67, respectively. This microsatellite set could be useful for population genetic studies of lark species widely differing in population fragmentation and conservation status across the Old World.

Spatial and Temporal Genetic Variation of Green Mussel, Perna viridis in the Gulf of Thailand and Implication for Aquaculture

The culture of green mussel (Perna viridis) in the Gulf of Thailand depends on natural spat which are believed to come from spawning grounds adjacent to major river mouths. In the present paper, genetic diversity of spatial and temporal populations of green mussel in the Gulf of Thailand was investigated using five microsatellite loci. The results showed moderate genetic variation of all 11 populations (averaged number of alleles per locus, A = 10.4-12.2; effective number of alleles per locus, A(e) = 5.36-6.59; mean allelic richness, A(r) = 10.23-12.06; observed heterozygosity, H(o) = 0.52-0.63, and expected heterozygosity, H(e) = 0.66-0.73) without significant differences among populations. No sign of bottleneck or genetic disequilibrium was observed. Genetic differentiation among spatial populations was low (F (ST) = 0.0046, CI(0.95) = 0.0020-0.0083 for the samples collected in January, 2007, and F (ST) = 0.0088, CI(0.95) = 0.0010-0.0162 for the samples collected in July, 2007) while temporal variation was significant as revealed by the analysis of molecular variance. Multidimensional scaling separated temporal population groups with minor exception. The assignment test revealed that most of the recruits were from other populations.

Genetic diversity assessment of sub-samples of cacao, Theobroma cacao L. collections in West Africa using simple sequence repeats marker

Knowledge of genebank and on-farm genetic diversity, particularly in an introduced crop species, is crucial to the management and utilization of the genetic resources available. Microsatellite markers were used to determine genetic diversity in 574 accessions of cacao, Theobroma cacao L., representing eight groups covering parental populations in West Africa, genebank, and farmers’ populations in Nigeria. From the 12 microsatellite markers used, a total of 144 alleles were detected with a mean allelic richness of 4.39 alleles/locus. The largest genetic diversity was found in the Upper Amazon parent population (Hnb = 0.730), followed by the 1944 Posnette’s Introduction (Hnb = 0.704), and was lowest in the Local parent population (Hnb = 0.471). Gene diversity was appreciably high in the farmers’ populations (Hnb = 0.563–0.624); however, the effective number of alleles was lower than that found in the genebank’s Posnette’s population. Fixation index estimates indicated deficiency of heterozygotes in the Upper Amazon and the Local parent populations (Fis = 0.209 and 0.160, respectively), and excess of heterozygotes in the Trinitario parent population (Fis = −0.341). The presence of inbreeding in the Local parent populations and substructure (Wahlund effect) in the Upper Amazon were suggested for the deficiency of heterozygotes observed. Non-significant genetic differentiation observed between the genebank’s and farmers’ populations indicated significant impact of national breeding programs on varieties grown in farmers’ plantations. From this study, we showed that appreciable genetic diversity was present in on-farm and field genebank collections of cacao that can be exploited for crop improvement in West Africa. Suggestions for future conservation of on-farm genetic diversity and local landraces are further discussed.

Genetic diversity and differentiation of sea trout (Salmo trutta) populations in Lithuanian rivers assessed by microsatellite DNA variation

The genetic diversity and differentiation of sea trout were studied in three river basins in Lithuania: Akmena-Dane, Bartuva, and Nemunas. A total of 282 individuals were genotyped at eight microsatellite loci. A similar level of genetic diversity was found in all of the populations studied: mean allelic richness ranged from 3.64 to 5.03, and average expected heterozygosity ranged from 0.588 to 0.721. Significant genetic divergence was observed among the different river basins as well as between populations within the drainages. All pairwise F (ST) values were highly significant, ranging from 0.027 to 0.197. The analysis of molecular variance showed rather weak hierarchical population structuring within the Nemunas basin, which may be explained by extensive gene flow among different river basins or, alternatively, reflect the influence of artificial breeding. Information on genetic diversity and differentiation of the Lithuanian sea trout populations will be useful for future management decisions.

The spatial genetic structure of bank vole (Myodes glareolus) and yellow-necked mouse (Apodemus flavicollis) populations: The effect of distance and habitat barriers

AbstractHabitat barriers are considered to be an important factor causing the local reduction of genetic diversity by dividing a population into smaller sections and preventing gene flow between them. However, the “barrier effect” might be different in the case of different species. The effect of geographic distance and water barriers on the genetic structure of populations of two common rodent species – the yellow-necked mouse (Apodemus flavicollis) and the bank vole (Myodes glareolus) living in the area of a lake (on its islands and on two opposite shores) was investigated with the use of microsatellite fragment analysis. The two studied species are characterised by similar habitat requirements, but differ with regard to the socio-spatial structure of the population, individual mobility, capability to cross environmental barriers, and other factors. Trapping was performed for two years in spring and autumn in north-eastern Poland (21°E, 53°N). A total of 160 yellow-necked mouse individuals (7 microsatellite loci) and 346 bank vole individuals (9 microsatellite loci) were analysed. The results of the differentiation analyses (FST and RST) have shown that both the barrier which is formed by a ca. 300 m wide belt of water (between the island and the mainland) and the actual distance of approximately 10 km in continuous populations are sufficient to create genetic differentiation within both species. The differences between local populations living on opposite lake shores are the smallest; differences between any one of them and the island populations are more distinct. All of the genetic diversity indices (the mean number of alleles, mean allelic richness, as well as the observed and expected heterozygosity) of the local populations from the lakeshores were significantly higher than of the small island populations of these two species separated by the water barrier. The more profound “isolation effect” in the case of the island populations of the bank vole, in comparison to the yellow-necked mouse populations, seems to result not only from the lower mobility of the bank vole species, but may also be attributed to other differences in the animals' behaviour.

Microsatellite, blood group and transferrin protein diversity of Estonian dairy cattle breeds

This study investigates genetic diversity within and among three Estonian dairy cattle breeds (Estonian Native, Estonian Red and Estonian Holstein). A total of 36 markers (25 microsatellites, 10 blood group systems and transferrin protein) were investigated and the within-breed diversity was quantified by expected heterozygosity, number of private alleles and mean allelic richness. The population structure was studied by computing the inbreeding coefficients, breed differentiation and relationships were investigated with random drift-based measures and a factorial correspondence analysis. In addition, a neighbour-joining tree was drawn summarising allele sharing distances for 195 individuals of the Estonian breeds, Western Finncattle, and Danish Jersey. The Estonian breeds displayed generally similar levels of within-population diversity. Depending on the set of markers used 6.2 or 4.3% of the total genetic variation can be explained by differences among the breeds. Construction of the tree for individuals revealed a distinctive pattern of grouping for Estonian Holstein, Estonian Red and Danish Jersey, but Estonian Native and Western Finncattle appeared on the same branches. This indicates that the gene pool of Estonian Native largely overlaps with that of Western Finncattle. However, our genetic marker analysis shows that the three Estonian breeds are genetically differentiated, suggesting that the current gene pool of Estonian dairy cattle is diverse.;

Genetic diversity and population structure of the endangered insect species Carabus variolosus in its western distribution range: Implications for conservation

Genetic variation was assessed in the endangered species C. variolosus (Coleoptera: Carabidae), which is listed in the European Habitats and Species Directive. Twelve populations from the north-western margin of its range in Germany and France to the border region between Slovenia and Croatia were investigated for variation at 16 allozyme loci. In general, genetic diversity was rather low as indicated by a mean allelic richness of 1.3 alleles per locus, a mean gene diversity (H E ) of 0.071 and a mean proportion of polymorphic loci (P 95% ) of 16%. Genetic diversity did not change directionally from the margin towards the core of the range. Very high differentiation between populations (overall F ST = 0.465), the results of a Mantel test, and poor accordance between geographical and genetic distance suggest a high degree of isolation of the island-like distributed populations. High F ST values and genetic distance measures, even between geographically close populations within the same drainage, confirm a very low dispersal power of this habitat specialist of headwater areas and swamps in woodlands, even in comparison with other flightless beetles. It is concluded that the majority of populations are demographically independent. Hierarchical F-statistics indicate that almost half of the genetic variance is found between regions and populations. Therefore, we recommend that conservation efforts consider every population as a management unit and aim to maintain as many populations as possible over as many regions as possible.

Genetic diversity and genetic structure of Northern Goshawk (Accipiter gentilis) populations in eastern Japan and Central Asia

Japanese goshawk was classified as a vulnerable species in the Red Data Book. There have been possibilities of a decrease of genetic diversity accompanied by habitat loss and genetic pollution due to hybridization with escaping imported goshawks. In this paper, genetic diversity, gene flow and conservation of Northern Goshawk (Accipiter gentilis) in Japan are discussed and compared with that in Central Asia. We used 11 newly developed microsatellite markers and also adopted six previously published markers. Genetic diversity was shown to be maintained with 0.58 as mean heterozygosity and 3.95 as mean allelic richness. The degree of genetic differentiation across all populations was low (Nei’s genetic differentiation index = 0.036, Wright’s genetic differentiation index = 0.039), possibly due to gene flow via adjacent regions (average number of migrants = 4.26; 0.68–20.30). However, it is possible that slight differentiation resulted from the short divergence time and/or inflow of escaping imported individuals. We recommend that goshawks in eastern Japan should be managed as a single unit. They do not appear to be under threat genetically at present, but there is the potential for rapid loss of genetic diversity. For future conservation, investigations of dispersal routes and actual conditions of gene flow are also recommended. To prevent further inflow of escaping goshawks into natural populations, it is desirable to reduce importation of goshawks and to enact a regulation obliging purchasers to register imported goshawks.

Development of a high-throughput microsatellite typing approach for forensic and population genetic analysis of wild and domestic African Bovini.

Conservation management and forensic traceability of African buffalo and cattle rely on the timely provision of unbiased and accurate genetic information. An approach in which 17 cattle microsatellite markers are co-electrophoresed, following amplification in three core multiplex reactions was established for this purpose. Mean allelic richness per locus was 8.24 and 6.47, for buffalo and Bonsmara cattle, respectively, whilst an unbiased match probability of 6.5x10-17 and 1.03 x 10-16 was obtained for each. These results confirm the usefulness of this rapid, cost-effective typing approach for forensic, paternity and fine-scale genetic analyses of wild and domestic African Bovini tribe members.

Genetic diversity and differentiation between the two remaining populations of the critically endangered Mediterranean monk seal

AbstractThe Mediterranean monk seal Monachus monachus, is a critically‐endangered species of which only two populations, separated by c. 4000 km, remain: the eastern Mediterranean (150–300 individuals) and the Atlantic/western Sahara populations (100–130 individuals). We measured current levels of nuclear genetic variation at 24 microsatellite loci in 12 seals from the eastern Mediterranean and 98 seals from the western Sahara population and assessed differences between them. In both populations, genetic variation was found to be low, with mean allelic richness for the loci polymorphic in the species of 2.09 and 1.96, respectively. For most loci, the observed allele frequency distributions in both populations were discontinuous and the size ranges similar. The eastern Mediterranean population had 14 private alleles and the western Sahara had 18, but with a much larger sample size. Highly significant differences in allele frequencies between the two populations were found for 14 out of 17 loci. FST between the two populations was 0.578 and the estimated number of migrants per generation was 0.046, both clearly indicating substantial genetic differentiation. From a conservation perspective, these results suggest that each population may act as a source for introducing additional genetic variation into the other population.

Genetic diversity and population size: island populations of the common shrew,Sorex araneus

Populations of many species are currently being fragmented and reduced by human interactions. These processes will tend to reduce genetic diversity within populations and reduce individual heterozygosities because of genetic drift, inbreeding and reduced migration. Conservation biologists need to know the effect of population size on genetic diversity, as this is likely to influence a population's ability to persist. Island populations represent an ideal natural experiment with which to study this problem. In a study of common shrews (Sorex araneus) on offshore Scottish islands, 497 individuals from 13 islands of different sizes and 6 regions on the mainland were trapped and genotyped at eight microsatellite loci. Previous genetic work had revealed that most of the islands in this study were highly genetically divergent from one another and the mainland. We found that most of the islands exhibited lower genetic diversity than the mainland populations. In the island populations, mean expected heterozygosity, mean observed heterozygosity and mean allelic richness were significantly positively correlated with log island size and log population size, which were estimated using habitat population density data and application of a Geographic Information System.