Population genetic structure of wild Phaseolus lunatus (Fabaceae), with special reference to population sizes

To set up an in situ conservation strategy for Phaseolus lunatus, we analyzed the genetic structure of 29 populations in the Central Valley of Costa Rica. Using 22 enzyme loci, we quantified the proportion of polymorphic loci (P(p)), the mean number of alleles per locus (A), and the mean effective number of alleles per locus (A(e)), which equaled to 10.32%, 1.10, and 1.05, respectively. The total heterozygosity (H(T)), the intrapopulation genetic diversity (H(S)), and the interpopulation genetic diversity (D(ST)) were 0.193, 0.082, and 0.111, respectively. The genotypic composition of the analyzed populations showed a deviation from the Hardy-Weinberg proportions (F(IT) = 0.932). This disequilibrium was due to either genetic differentiation between populations (F(ST) = 0.497) or nonrandom mating within populations (F(IS) = 0.866). From the level of genetic differentiation between populations and the private alleles frequencies estimates, gene flow was calculated: Nm(W) = 0.398 and Nm(S) = 0.023, respectively. The results suggested that wild Lima bean maintains most of its isozyme variation among populations. Significant positive correlation was observed between population size and P(p), A, and H(o) (observed heterozygosity), whereas no correlation was observed with the average fixation index of population (F). The loss of genetic variability in populations was attributed to inbreeding and the bottleneck effects that characterized the target populations. In situ conservation and management procedures for wild Lima bean are discussed.     

Genetic variability in captive populations of Crocodylus moreletii (Crocodylia: Crocodylidae) using microsatellites markers

Crocodylus moreletii, an extinction threatened species, represents an emblem for tropical ecosystems in Mexico. Surprisingly, there is a lack of information about their genetic constitution, which should be evaluated for a proper management ex situ and for making decisions on the release of crocodiles into natural habitats. The aim of this study was to characterize and compare the genetic variability of four populations of C. moreletii (two wild versus two born ex situ). Through PCR were amplified seven microsatellite polymorphic loci, however a heterozygote deficit, diminished by the presence of null alleles, was found in the populations (average Ho=0.02). The AMOVA indicated that the highest proportion of genetic variability is within populations, and a limited genetic differentiation among populations (average F(ST)=0.03), probably due to high inbreeding index (average F(IS)=0.97). When comparing the genetic variability between and within other crocodilian species, we found that in C. moreletii is well below those reported. We concluded that the limited genetic variability in ex situ born populations is probably due to a founder effect derived from the social structure of their progenitors, and by the bottleneck effect, inferred by the limited effective population size, that historically characterizes their natural distribution in wild populations.     

Low genetic structure in an epiphytic Orchidaceae (Oncidium hookeri) in the Atlantic rainforest of South-eastern Brazil

BACKGROUND AND AIMS: Oncidium hookeri is a neotropical species of epiphytic Orchidaceae found in the Brazilian Atlantic rainforest at the top of the Mantiqueira Range of mountains. The genetic variation of O. hookeri was studied to assess the distribution of genetic variability within and among six populations localized in Atlantic rainforest remnants. Gene flow among populations and the occurrence of recent bottlenecks were investigated in order to infer the degree of isolation of these populations. METHODS: Thirteen polymorphic loci were used for allozyme electrophoresis. The data were analysed by means of standard statistical approaches, to estimate gene diversity and the genetic structure of the populations. KEY RESULTS: The mean gene diversity and allelic richness were H(e) = 0.099 and A = 1.75, respectively. F-statistics revealed high heterozygote deficiencies in all populations (F(IS) = 0.43-0.82). Several rare alleles were found in all the populations, and three populations presented private alleles. Low genetic differentiation among O. hookeri populations was detected (F(ST) = 0.029); natural selection may be involved in PGM locus differentiation among populations. The genetic differentiation between paired populations was low, bearing no correlation with geographic distance (Mantel test: r = -0.34, P = 0.72). Only two populations showed signs of recent bottlenecks. CONCLUSIONS: The heterozygote deficiency found seems to be caused by pollinator behaviour; the low frequencies of several alleles of different loci can be maintained due to clonal propagation. Despite the stochastic nature of the wind-dispersal of seeds to long distances, this process may promote an effective gene flow among populations, thus avoiding genetic differentiation.     

Partitioning and diversity of nuclear and organelle markers in native and introduced populations of Epipactis helleborine (Orchidaceae)

Variability of allozymes (1170 individuals, 47 populations) and chloroplast DNA (692 individuals, 29 populations) was examined in native European and introduced North American populations of Epipactis helleborine (Orchidaceae). At the species level, the percentage of allozyme loci that were polymorphic (P(99)) was 67%, with a mean of 2.11 alleles (A) per locus, and an expected heterozygosity (H(exp)) of 0.294. At the population level, mean P(99) = 56%, mean A = 1.81, and mean H(exp) = 0.231. Although field observations suggest that self-pollination occurs frequently, populations had a genetic structure consistent with Hardy-Weinberg expectations and random mating (mean F(IS) = 0.002). There was significant deviation from panmixia associated with population differentiation (mean F(ST) = 0.206). The distribution of two chloroplast haplotypes showed that 15 of the 29 populations were polymorphic. Using both nuclear and organelle F(ST) estimates, a pollen to seed flow ratio of 1.43?:?1 was calculated. This is very low compared with published estimates for other plant groups, consistent with the high dispersability of orchid seeds. Finally, there was no evidence for a genetic bottleneck associated with the introduction of E. helleborine to North America.     

Isozyme variability of the wetland specialist Swertia perennis (Gentianaceae) in relation to habitat size, isolation, and plant fitness

We examined the effects of size and spatial isolation of fens on the isozyme variability of 17 populations of Swertia perennis. This long-lived perennial is a locally abundant fen specialist in Switzerland, where wetlands have been strongly fragmented. Isozyme variability was comparable to other outcrossing plants (A = 1.53, AP(p) = 2.01, P(p) = 42.5, H(o) = 0.113, H(e) = 0.139). F statistics indicated both inbreeding within and differentiation between populations (F(IS) = 0.076, F(IT) = 0.194, F(ST) = 0.128), with moderate gene flow between populations (N(e)m = 1.703). Populations in small, isolated fens had reduced genetic variability and the highest within-population inbreeding coefficients (F(IS)). Isozyme variability was significantly associated with vegetative fitness traits (MANOVA), and the magnitude of leaf herbivory decreased as the percentage of polymorphic loci increased. These data suggest that the reduced genetic variability of S. perennis in small, isolated populations may reduce plant fitness, thereby increasing susceptibility to herbivore damage. Our study also shows that habitat fragmentation can reduce the genetic variability of populations of fairly common habitat specialists, which so far have attracted less conservation attention than rare species.     

Analysis of microsatellite DNA markers reveals no genetic differentiation between wild and hatchery populations of Pacific threadfin in Hawaii

Pacific threadfin, Polydactylus sexfilis, is popular fish in recreational fishing, as well as aquaculture in Hawaii. Its natural population has been continuously declining in the past several decades. Microsatellite DNA markers are useful DNA-based tool for monitoring Pacific threadfin populations. In this study, fifteen Microsatellite (MS) DNA markers were identified from a partial genomic Pacific threadfin DNA library enriched in CA repeats, and six highly-polymorphic microsatellite loci were employed to analyze genetic similarity and differences between the wild population and hatchery population in Oahu Island. A total of 37 alleles were detected at the six MS loci in the two populations. Statistical analysis of fixation index (F(ST)) and analysis of molecular variance (AMOVA) showed no genetic differentiation between the wild and hatchery populations (F(ST) = 0.001, CI(95%) = -0.01-0.021). Both high genetic diversity (H(o) = 0.664-0.674 and H(e) = 0.710-0.715) and Hardy-Weinberg equilibrium were observed in the wild and hatchery populations. Results of genetic bottleneck analysis indicated that the hatchery was founded with sufficient numbers of brooders as inbreeding coefficient is very low (F(IS) = 0.052-0.072) in both wild and hatchery populations. Further studies are needed for comprehensive determinations of genetic varieties of primary founder broodstocks and successive offspring of the hatchery and wild populations with increased number of Pacific threadfin sample collections.     

Genetic Polymorphism and Bottleneck Analysis of Balkhi,Hashtnagri, and Michni Sheep Populations Using Microsatellite Markers

Pakistan is rich in sheep genetic resources. Balkhi, Hashtnagri, and Michni are neighboring sheep populations found in Khyber Pakhtunkhwa province of Pakistan. In this study, we analyzed the genetic structures and bottleneck incidents within these sheep populations using 31 microsatellite DNA markers. Total numbers of 116, 100, and 95 alleles, with average numbers of 3.20, 3.26, and 3.74 alleles per locus were observed, respectively, in Balkhi, Hashtnagri, and Michni population. Mean observed heterozygosity was 0.402 in Balkhi, 0.416 in Hashtnagri, and 0.522 in Michni population. All the three sheep populations showed significantly high inbreeding. Michni population was found to be in mutation drift equilibrium, showing the absence of genetic bottleneck. The data of Balkhi and Hashtnagri indicated the presence of genetic bottleneck in these populations. These results suggest a moderate level of genetic diversity within Michni population that may be useful for breed improvement programs. Hashtnagri and Balkhi populations having low within breed genetic variability may contain some valuable characteristics that need to be conserved.     

四个不同地理区域的库蚊复合组居群的遗传多样性研究

库蚊种群在农药强选择压下的生存及抗性进化是与其种群的遗传多样性密切相关的。本文主要从居群的遗传多样性角度出发 ,研究其抗性遗传行为。分别对采自 4个不同地理区域的库蚊复合组样群 ,采用水平切片淀粉凝胶电泳的方法 ,分析了 3个酶系统 (苹果酸酶Me、苹果酸脱氢酶Mdh、甘油醛-3-磷酸脱氢酶Gpd) ,获得了 5个位点共 2 7个等位基因的资料。并计算了 4个库蚊居群的遗传多样性指标为 (A ,P ,He,Ho) ,同时分析了 5种居群间的遗传距离。分析结果表明 :遗传多样性主要存在于各居群之内 (FIS=0 .5 4 37) ,但居群之间的遗传分化程度也相对较大 (Gst =0 .4 498)。     

High selfing and high inbreeding depression in peripheral populations of Juncus atratus

The mating system of a plant is the prime determinant of its population genetic structure. However, mating system effects may be modified by postzygotic mechanisms like inbreeding depression. Furthermore, historical as well as contemporary ecological factors and population characteristics, like the location within the species range can contribute to genetic variability. Using microsatellite markers we assessed the population genetic structure of the wind-pollinated Juncus atratus in 16 populations from peripheral and nearly central areas of the distribution range and studied the mating system of the species. In three peripheral populations, outcrossing rates at seeds stage were low (mean t(m) = 5.6%), suggesting a highly autogamous mating system. Despite this fact, on adult stage both individual heterozygosity (mean H(O) = 0.48) and gene diversity (mean H(E) = 0.58) were high even in small populations. Inbreeding coefficients were consistently low among all populations (mean F(IS) = 0.15). Within the three peripheral populations indirect estimates of lifetime inbreeding depression were surprisingly high (delta(eq) = 0.96) and inbreeding depression could be shown to act mostly on early seedling establishment. Similar conditions of autogamy combined with high inbreeding depression are typical for plants with a large lifetime genomic mutation rate that cannot avoid selfing by geitonogamy. However, the results presented here are unexpected for small-statured, herbaceous plants. Substantial genetic differentiation among all populations was found (mean F(ST) = 0.24). An isolation-by-distance pattern was apparent on large scale but not on local scale suggesting that the overall pattern was largely influenced by historical factors, e.g. colonization, whereas locally genetic drift was of greater importance than gene flow. Peripheral populations exhibited lower genetic diversity and higher inbreeding coefficients when compared with subcentral populations.     

Colonization, genetic diversity, and evolution in the Swedish sand lizard, Lacerta agilis (Reptilia, Squamata)

The Swedish sand lizard ( Lacerta agilis ) is a relict species from the post-glacial warmth period. From the geological history of this region, and more recent data on population fragmentation due to disturbance by man, it can be surmised that the Swedish sand lizards passed through at least one population bottleneck in relatively recent times. We tested this hypothesis by investigating the amount and structuring of genetic variability in six microsatellite loci in ten lizard populations from different parts of Sweden. We contrasted these data against those from a Hungarian population which we have reason to assume strongly resembles the founder population for Swedish sand lizards. The average number of alleles per locus in Sweden was 3.3, and these alleles were common in almost all populations, whereas the average number of alleles in the Hungarian population was 8.0. Likewise, the level of expected heterozygosity was lower in the Swedish populations (0.45) compared to the Hungarian population (0.70). The lower variability in Swedish populations is probably a consequence of a common population bottleneck during the immigration subsequent to the latest glacial period. The remaining variability is strongly subdivided between populations (F_ST=0.30) with the main genetic differences being between rather than within populations. Despite the marked isolation of the populations and the present small population sizes (N= 10–300 adults), the Swedish relict populations show a surprisingly high level of observed heterozygosity, indicating that small population size is probably a recent phenomenon.     

Isolation and characterization of 10 microsatellite loci in Cneorum tricoccon (Cneoraceae), a Mediterranean relict plant

? Premise of the study: The main aim of this study was to isolate and characterize microsatellite loci in Cneorum tricoccon (Cneoraceae), a Mediterranean shrub relict of the early Tertiary, which inhabits western Mediterranean islands and coasts. Microsatellites will be useful for investigating biogeography and landscape genetics across the species distribution range, including current or past gene flow. ? Methods and Results: Seventeen microsatellite loci were characterized, of which 10 were polymorphic and amplified for a total of 56 alleles in three populations of C. tricoccon. The markers revealed average coefficients of expected heterozygosity (H(e) = 0.425), observed heterozygosity (H(o) = 0.282), and inbreeding coefficient value per population (F(IS) = 0.408). ? Conclusions: These microsatellite primers will potentially be useful in the study of population and landscape genetics, conservation status of isolated populations, island-continental distribution, current or historical movements between populations, and in the investigation of the consequences of dispersal mechanisms of these plants.     

Detecting bottlenecks using BOTTLENECK 1.2.02 in wild populations: the importance of the microsatellite structure

Reduced, or bottlenecked, populations are more prone to adverse events. Thus, the detection of genetic bottleneck signatures in wildlife is an important issue for conservation. BOTTLENECK 1.2.02 is a software commonly used for detecting genetic characteristics of past bottlenecks. Here we test the efficiency with which this software detects bottlenecks in two koala populations of known history. The sign test performed well for both populations, particularly under the infinite alleles model for mutation. This suggests this model could be the more realistic for marsupial microsatellites than other mutation models. Under the allele frequency distribution test, the two populations falsely appeared to be at mutation/drift equilibrium. However, this test could detect the bottleneck when only imperfect repeat microsatellites were included in the analysis. We thus recommend further investigation of imperfect repeat microsatellites, which could be more powerful for bottleneck detection. These results underline the cautious approach researchers and conservationists should take when studying the past of unknown populations.     

Founder effects and the genetic structure of Coulter pine

Mean expected heterozygosity at 33 isozyme loci decreased with latitude from 0.193 near the southern extreme of Coulter pine's range to 0.107 at its northern extreme. This decrease was paralleled by a loss of alleles north of the Peninsular Ranges of southern California. Fifteen alleles dropped out along the roughly lineal range, at points coincident with large gaps in the species' distribution. The pattern may reflect a cascading series of founder events as Coulter pine invaded the Trans. verse Ranges and the South Coast Ranges from Pleistocene refugia. Alleles were not replaced following colonization, probably because migration, Nm, among populations is only 0.74-1.27, depending on estimator, the lowest values reported in any pines. Wright's (F(ST)) indicated that 16.5% of the total genic diversity is among populations. The fixation index, (F(IS)) of 0.072 indicated only a moderate excess of homozygotes. However, the northernmost outlier had significant excess homozygosity (F = 0.253). Hybridization may also play a role in the genetic structure of Coulter pine: 16 alleles were novel, or private, occurring only where Coulter pine was sympatric with Jeffrey pine, particularly at San Benito Mountain. Some of these novel alleles could be the result of introgression from Jeffrey pine, or possibly represent hybrizymes, products of intragenic recombination between genomes.     

Genetic variation and differentiation in captive and wild zebra finches (Taeniopygia guttata)

The zebra finch (Taeniopygia guttata) is a small Australian grassland songbird that has been domesticated over the past two centuries. Because it is easy to breed in captivity, it has become a widely used study organism, especially in behavioural research. Most work has been conducted on domesticated populations maintained at numerous laboratories in Europe and North America. However, little is known about the extent to which, during the process of domestication, captive populations have gone through bottlenecks in population size, leading to inbred and potentially genetically differentiated study populations. This is an important issue, because (i) behavioural studies on captive populations might suffer from artefacts arising from high levels of inbreeding or lack of genetic variation in such populations, and (ii) it may hamper the comparability of research findings. To address this issue, we genotyped 1000 zebra finches from 18 captive and two wild populations at 10 highly variable microsatellite loci. We found that all captive populations have lost some of the genetic variability present in the wild, but there is no evidence that they have gone through a severe bottleneck, as the average captive population still showed a mean of 11.7 alleles per locus, compared to a mean of 19.3 alleles/locus for wild zebra finches. We found significant differentiation between the captive populations (F(ST) = 0.062). Patterns of genetic similarity closely match geographical relationships, so the most pronounced differences occur between the three continents: Australia, North America, and Europe. By providing a tree of the genetic similarity of the different captive populations, we hope to contribute to a better understanding of variation in research findings obtained by different laboratories.     

Genetic variation and evolution of Polaskia chichipe (Cactaceae) under domestication in the Tehuacán Valley, central Mexico

Polaskia chichipe is a columnar cactus under artificial selection in central Mexico because of its edible fruits. Our study explored the effect of human manipulation on levels and distribution of genetic variation in wild, silviculturally managed and cultivated sympatric populations. Total genetic variation, estimated in nine populations with five microsatellite loci, was H(T) = 0.658 +/- 0.026 SE, which was mainly distributed within populations (H(S) = 0.646) with low differentiation among them (F(ST) = 0.015). Fixation index (F(IS)) in all populations was positive, indicating a deficit of heterozygous individuals with respect to Hardy-Weinberg expectations. When populations were pooled by management type, the highest expected heterozygosity (H(E) = 0.631 +/- 0.031 SE) and the lowest fixation index (F(IS) = 0.07) were observed in wild populations, followed by cultivated populations (H(E) = 0.56 +/- 0.03 SE, F(IS) = 0.14), whereas the lowest variation was found in silviculturally managed populations (H(E) = 0.51 +/- 0.05 SE, F(IS) = 0.17). Low differentiation among populations under different management types (F(ST) 0.005, P < 0.04) was observed. A pattern of migration among neighbouring populations, suggested from isolation by distance (r2 = 0.314, P < 0.01), may have contributed to homogenizing populations and counteracting the effects of artificial selection. P. chichipe, used and managed for at least 700 generations, shows morphological differentiation, changes in breeding system and seed germination patterns associated with human management, with only slight genetic differences detected by neutral markers.     

Microsatellite DNA typing for assessment of genetic variability in Tharparkar breed of Indian zebu (Bos indicus) cattle, a major breed of Rajasthan

The present study estimates genetic variability with a set of 25 microsatellite markers in a random sample of 50 animals of Tharparkar breed of Indian zebu (Bos indicus) cattle. Tharparkar is a dual-purpose breed, valued for its milk as well as draught utility, and is adapted to the inhospitable Thar desert conditions of Rajasthan typified by summer temperature hovering above 50 degrees C, sparse rainfall and vegetation, and scarcity of even drinking water. The observed number of alleles ranged from 4 (ETH3, ILSTS030, INRA5, INRA63 and MM8) to 11 (HEL9 and ILSTS034), with allelic diversity (average number of observed alleles per locus) of 6.20. Observed and expected heterozygosity ranged from 0.25 (INRA63) to 0.77 (ETH10), and from 0.51 (HEL5 and HAUT27) to 0.88 (HEL9) respectively. Wide range of genetic variability supported the utility of these microsatellite loci in measurement of genetic diversity indices in other Indian cattle breeds too. Various average genetic variability measures, namely allele diversity (6.20), observed heterozygosity (0.57), expected heterozygosity (0.67) and mean polymorphism information content (0.60) values showed substantial within-breed genetic variability in this major breed of Rajasthan, despite accumulated inbreeding as reflected by high average inbreeding coefficient (F(IS) = 0.39). The Tharparkar population has not experienced a bottleneck in the recent past.     

Genetic structure of an endangered plant, Antirrhinum microphyllum (Scrophulariaceae): allozyme and RAPD analysis

Thirteen allozyme loci and 68 random amplified polymorphic DNA (RAPD) markers were analyzed to assess the genetic diversity and population structure of threatened Antirrhinum microphyllum (Scrophulariaceae), a narrow endemic of central Spain known from only four populations. According to allozyme data, species genetic diversity (p = 46.15%, A = 2.61, and H(e) = 0.218), as well as within-population genetic diversity (p = 44.23%, A = 2.10, and H(e) = 0.204), were high when compared to average estimates for other narrowly distributed plant species. Ninety-four percent of species genetic diversity corresponded to within-population genetic diversity. Nevertheless, significant differences were found among populations in allele frequencies of four of the six polymorphic loci, and three private alleles were detected. Inbreeding coefficients (F(IS)) suggest that populations are structured in genetic neighborhoods. The RAPDs also showed high levels of genetic diversity (p = 89.71% and H(e) = 0.188 at the species level, and p = 67.65% and H(e) = 0.171 at the population level). Nei's genetic distances estimated both from allozymes and RAPDs indicated low differentiation among populations. In spite of this, the low frequencies of certain alleles and the presence of private alleles indicate that efforts should be made to conserve all four remaining populations.     

Genetic diversity and the reproductive system in related species of antirrhinum

BACKGROUND AND AIMS: Seven related species of Antirrhinum (A. siculum, A. majus, A. latifolium, A. linkianum, A. litigiosum, A. cirrhigherum and A. tortuosum) were studied in order to compare levels of genetic variation and its partitioning in them, and to check relationships between genetic patterns and the reproductive system. METHODS: Eight hundred and fifty-one plants were screened for variability at 13 allozyme loci by means of horizontal starch gel electrophoresis. Parameters of genetic diversity and its partitioning, the inbreeding coefficient as well as an indirect estimate of gene flow based on the equation: Nm = (1 - G(ST))/4G(ST), were calculated. KEY RESULTS: Genetic variability in A. siculum was found to be the lowest known in the genus. Mean values of F(IT) and F(IS) were mostly positive and not significantly different from zero. Population differentiation (F(ST)) ranged between 6.1 in A. tortuosum and 17.6 in A. linkianum. The inbreeding coefficient within populations ranged between F(IS) = -0.5 in A. tortuosum and F(IS) = 1 in A. siculum. Estimates of gene flow ranged between Nm = 15 in A. majus (considered as very high) to Nm = 0.42 in A. siculum (considered as low). CONCLUSIONS: Correlation was found between levels of diversity and differentiation on one hand, and the reproductive system of the studied taxa on the other. Striking differences among species in the inbreeding coefficient (F(IS)) show different reproductive systems, which mostly support previous reports. Strategies for the conservation of A. siculum are recommended, such as preservation of natural populations as well as ex situ preservation of seeds from different populations.     

Genetic structure and conservation of Mountain Lions in the South-Brazilian Atlantic Rain Forest

The Brazilian Atlantic Rain Forest, one of the most endangered ecosystems worldwide, is also among the most important hotspots as regards biodiversity. Through intensive logging, the initial area has been reduced to around 12% of its original size. In this study we investigated the genetic variability and structure of the mountain lion, Puma concolor. Using 18 microsatellite loci we analyzed evidence of allele dropout, null alleles and stuttering, calculated the number of allele/locus, PIC, observed and expected heterozygosity, linkage disequilibrium, Hardy-Weinberg equilibrium, F(IS), effective population size and genetic structure (MICROCHECKER, CERVUS, GENEPOP, FSTAT, ARLEQUIN, ONESAMP, LDNe, PCAGEN, GENECLASS software), we also determine whether there was evidence of a bottleneck (HYBRIDLAB, BOTTLENECK software) that might influence the future viability of the population in south Brazil. 106 alleles were identified, with the number of alleles/locus ranging from 2 to 11. Mean observed heterozygosity, mean number of alleles and polymorphism information content were 0.609, 5.89, and 0.6255, respectively. This population presented evidence of a recent bottleneck and loss of genetic variation. Persistent regional poaching constitutes an increasing in the extinction risk.     

Genetic diversity and differentiation of dromedarian camel of India

Estimation of genetic variability and relationship among different livestock breeds is important for management of genetic resources for their sustainable utilization and conservation. This is more important when the livestock species, like camel, have shown a sharp decline in head count during the last decade. In the present study we estimated genetic variability and relationship among four camel breeds of India using 23 microsatellite loci. A total of 252 alleles were observed across all the four populations with mean number of alleles per locus as 8.04, 7.30, 6.39, and 7.43 for Bikaneri, Jaisalmeri, Kutchi, and Mewari breeds, respectively. The mean observed heterozygosity of the four breeds were 0.58, 0.57, 0.56, and 0.60 for Bikaneri, Jaisalmeri, Kutchi, and Mewari breeds, respectively and were lower than expected heterozygosity values. The mean estimates of F statistics were 0.227+/-0.044 (F(IT)), 0.157+/-0.038 (F(IS)), and 0.082+/-0.019 (F(ST)). The values were significantly different from zero for all the three measures and point towards the existence of population structure and moderate differentiation in four camel breeds. The exact test also indicated significant population differentiation (P < 0.001). The analysis of molecular variance revealed 12% of the variation attributed to among populations and 88% within populations. Sixty-nine percent of the individuals could be correctly assigned using "leave one out" procedure. All the individuals of Mewari and 42 out of 44 Jaisalmeri were correctly assigned. The existence of strong population structure in Jaisalmeri and Mewari camel was further substantiated by Nei's standard genetic distance as well as interindividual allele sharing distance. Thus these two breeds owing to selection for specific traits are distinct from other camel breeds.