ΦST Values Research Articles

Genetic diversity of six arable plants in relation to their Red List status

In Central Germany and throughout Europe, arable plants count among some of the most endangered plant species. Over the last few decades, the number and size of populations have been in sharp decline due to modern land use techniques, including the application of fertilizers, herbicide use and seed cleaning procedures. As arable plant species are underrepresented in population genetic studies, it is unknown whether agricultural intensification has affected the extant populations, and whether genetic structure varies among species with differing vulnerability in respect of their Red List status. We sampled 53 populations from 6 arable plant species throughout Central Germany. Random amplified polymorphic DNA analyses (RAPD) were applied to calculate measures of genetic diversity at the population level and genetic differentiation. Genetic diversity was found to be lowest in Bupleurum rotundifolium and Anagallis foemina, and highest in Consolida regalis and Nigella arvensis. The highest levels of genetic differentiation were observed among populations of An. foemina and B. rotundifolium but within populations in all other species. ΦST values differed strongly ranging between 0.116 for C. regalis and 0.679 for An. foemina. Patterns of genetic structure were related to the Red List status for all the species studied except An. foemina, for which it should consequently be raised. Our data confirm that even relatively recent threats are accompanied by detrimental genetic structure. As losses of populations and increased fragmentation have occurred in all common and uncommon species, the situation for arable plants could change for the worse in the following decades, highlighting the need for consistent monitoring.

Low genetic diversity and genetic differentiation among domesticated stocks of the small abalone Haliotis diversicolor in China

AFLP markers were used to investigate levels of genetic diversity within cultured populations of the small abalone Haliotis diversicolor in China and to compare them with a wild population. A total of 234 fragments, with a size range of 150-500 bp, were identified from 152 individuals by five AFLP primer combinations. High proportion of polymorphic loci (77.65%) and heterozygosity (0.2124) were found within the natural population, while low proportion of polymorphic loci (24.51 to 64.31%) and heterozygosity (0.0677 to 0.1665) were detected within the six cultured populations. The results show a significantly reduced genetic diversity in the hatchery stocks when compared with the wild population. AMOVA analysis, pairwise comparison of φST values, and cluster analysis showed that both the wild population (DX) and the stock (TW) were significantly different from the other five domestic cultured populations. For the five hatchery stocks sampled from mainland China coast, however, genetic differences were not significant, except between SZ and ZJ, SZ and HN stocks. The genetic status detected in this study hints that mass mortality of H. diversicolor in recent years might have association with the reduction in genetic diversity. The results also indicate that all cultured populations, excluding TW and ZJ stocks, may not be suitable as source populations for selective breeding programs; some natural populations and foreign stocks introduced from outside China should be considered. Key words : Amplified fragment length polymorphism, Haliotis diversicolor , domesticated stocks, geneticdiversity.

SSR-based population structure, molecular diversity and linkage disequilibrium analysis of a collection of flax (Linum usitatissimum L.) varying for mucilage seed-coat content

Flax seed mucilage (SM) presents specific biological activities useful for the food and pharmaceutical industries. Understanding the population structure, genetic diversity and linkage disequilibrium (LD) of germplasm varying for mucilage content is pivotal for the identification of genes and quantitative trait loci underlying mucilage variation by association mapping (AM). In this study, 150 microsatellite loci were used to assess the population structure, genetic diversity and LD of a set of 60 flax cultivars/accessions capturing the breadth of SM variation in flax germplasm. STRUCTURE analysis and similarity-based methods revealed the presence of three populations reflecting mainly their geographic origins (South Asia, South America and North America), and the impact of germplasm exchange within and between North American flax breeding programs. Analysis of molecular variance showed that 78.32% of the genetic variation resided within populations and 21.68% among populations. The phi-statistic (Φst) value of 0.22 confirmed the presence of a strong population structure. A total of 408 alleles were detected, with the South American population capturing the highest overall diversity. However, the genetic diversity was narrow, as indicated by the small number of alleles per locus (2.72) and gene diversity (mean = 0.34). LD was significant between 3.9% (r 2) and 36.2% (D′) of the loci pairs (FDR < 0.05). The mean r 2 and D′ were 0.26 and 0.53, respectively. The results suggest that the collection could be useful in AM studies aimed at the discovery of genes/alleles involved in SM; however a greater diversity may be required to improve the AM resolution.

Evaluation of Genetic Diversity and Population Structure of Panonychus citri (Acari: Tetranychidae) in China using Ribosomal Internal Transcribed Spacer 1 Sequences

Abstract The citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), has a world-wide distribution and is the most important citrus (Citrus spp.) pest in many countries, including Japan, Spain, and China. To characterize the population genetic structure of the citrus red mite, the genetic variation in 15 populations from three citrus-planting regions of China (citrus belt of upper and middle reaches of Yangtze River [UMYR], citrus base of Yungui Plateau [YGP], and citrus belt of South China [SC]) was investigated using the ribosomal internal transcribed spacer (ITS) 1 region. These populations were characterized by high genetic diversity. Neutrality tests, mismatch analysis, and star-like network strongly supported the population expansion. Analysis of molecular variance (AMOVA) showed that no significant population genetic structure existed among UMYR, YGP, and SC. However, a significant global φST and the genetic structure were found between (UMYR + YGP) and SC. Pairwise φST values between most populations were not significant, and a high gene flow was found among some geographically distant populations. The significant influence of host plants on the genetic structure of P. citri populations was found by the AMOVA for five host-related groups. In addition, the Mantel test revealed that geographical isolation was a factor responsible for the genetic differentiation. Therefore, our current observed population structure of P. citri can be contribute to several factors together, i.e., ongoing gene flow, the retention of ancestral polymorphisms, and natural selection (e.g., host plants, acaricides).

Genetic variation of Laminaria japonica (Phaeophyta) populations in China as revealed by RAPD markers

For the population genetics analysis of the naturally grown brown seaweed Laminaria japonica (Laminariales, Phaeophyta) sampled from Dalian, Yantai, Weihai, Rongcheng and Qingdao in China, ten primers were employed to produce 88 bands as revealed by randomly amplified polymorphic DNA (RAPD) markers, and all these bands were polymorphic. According to these band patterns, there were 94 distinct phenotypes occurred in 100 samples indicating the high heterozygosity of this kelp. Dalian population samples showed the highest percentage of polymorphism (71.67%), and also the higher diversity estimated on the basis of the Shannon’s index (8.498), suggesting that this population could be chosen as the best resource for genetic breeding. The highest diversity of Yantai population possibly resulted from the introduction of L. longissima used for interspecific cross breeding with L. japonica cultivated in China. From Dalian southwards to Qingdao, the genetic variation of the five populations became less with a decrease in latitude, possibly due to the natural selection especially of high temperature. The genetic distance (ΦST values) of the five populations was a little significantly correlated with the geographical distance (r=0.496) at P=0.05 by Mantel’s test. Weihai, Rongcheng and Yantai populations were closely grouped genetically together by Neighbor-joining cluster analysis probably in that the dispersal of the kelp by propagules more easily occurring in the range of relatively short distance. The analysis of molecular variance (AMOVA) also demonstrated that the relatively higher variation occurred among populations (71.49%) at an extremely significant level (P<0.000 1). All these evidence showed that there was a relatively distinct genetic differentiation among the sampled kelp populations, and L. japonica grown in China was also rather heterozygous in heredity.

Polymorphism in a common Atlantic reef coral (Montastraea cavernosa) and its long-term evolutionary implications

Recent advances in morphometrics and genetics have led to the discovery of numerous cryptic species in coral reef ecosystems. A prime example is the Montastraea annularis scleractinian coral species complex, in which morphological, genetic, and reproductive data concur on species boundaries, allowing evaluation of long-term patterns of speciation and evolutionary innovation. Here we test for cryptic species in the Atlantic species, Montastraea cavernosa, long recognized as polymorphic. Our modern samples consist of 94 colonies collected at four locations (Belize, Panama, Puerto Rico in the Caribbean; Sao Tome in the Eastern Atlantic). Our fossil samples consist of 78 colonies from the Plio-Pleistocene of Costa Rica and Panama. Landmark morphometric data were collected on thin sections of 46 modern and 78 fossil colonies. Mahalanobis distances between colonies were calculated using Bookstein coordinates, revealing two modern and four fossil morphotypes. The remaining 48 of the 94 modern colonies were assigned to morphotype using discriminant analysis of calical measurements. Cross-tabulation and multiple comparisons tests show no significant morphological differences among geographic locations or water depths. Patterns of variation within and among fossil morphotypes are similar to modern morphotypes. DNA sequence data were collected for two polymorphic nuclear loci (β-tub1 and β-tub2) on all 94 modern colonies. Haplotype networks show that both genes consist of two clades, but morphotypes are not associated with genetic clades. Genotype frequencies and two-locus genotype assignments indicate genetic exchange across clades, and ϕst values show no genetic differentiation between morphotypes at different locations. Taken together, our morphological and genetic results do not provide evidence for cryptic species in M. cavernosa, but indicate instead that this species has an unusually high degree of polymorphism over a wide geographic area and persisting for >25 million years (myr).

Genetic structure of coastal and inland populations of Spergularia media (L.) C. Presl (Caryophyllaceae) in Central Europe

In Central Europe, salt-influenced habitats are restricted mainly to the coastlines of the North Sea and the Baltic Sea. The few natural inland salt sites suffer from size reduction and loss in biodiversity, while anthropogenic salt sites around potash mining dumps experienced recent and massive de novo colonization by numerous halophytes. Our study aimed to elucidate the general patterns of gene flow among coastal and inland salt habitats. We used amplified fragment length polymorphisms to assess the genetic diversity and genetic structure of 18 European populations of the halophyte Spergularia media (Caryophyllaceae), sampled from inland and coastal salt sites of Germany, the Netherlands, Denmark, Austria, France and Italy. Estimates of genetic diversity on the population level were generally low, especially within inland salt habitats. Analyses of molecular variance showed comparatively strong differentiation among populations. Multivariate ordination (principal coordinate analysis) and a NeighborNet analysis revealed four distinct groups of populations that showed good correspondence to their geographic origins. A Bayesian analysis performed with the program Structure as well as high pairwise Φ ST values supported the results of the phenetic analyses. The observed patterns of diversity and differentiation among inland populations of S. media are best explained by the isolated nature of suitable salt habitats, with concomitant reduction of gene flow to and among these sites. Our data support the hypothesis that the colonization of anthropogenic salt sites by S. media originated from natural inland habitats.

Evidence for extensive population structure in the white‐spotted eagle ray within the Indo‐Pacific inferred from mitochondrial gene sequences

The white-spotted eagle ray Aetobatus narinari is a species complex that occurs circumglobally throughout warm-temperate waters. Aetobatus narinari is semi-pelagic and large (up to 300 cm disc width), suggesting high dispersal capabilities and gene flow on a wide spatial scale. Sequence data from two mitochondrial genes, cytochrome b (cytb) and NADH dehydrogenase subunit 4 (ND4), were used to determine the genetic variability within and among 18 sampling locations in the central Indo-Pacific biogeographical region. Populations in the Indo-Pacific were highly genetically structured with c. 70% of the total genetic variation found among three geographical regions (East China Sea, Southeast Asia and Australia). FST was 0.64 for cytb and 0.53 for ND4, with φST values being even larger, that is, 0.78 for cytb and 0.65 for ND4. This high-level genetic partitioning provides strong evidence against extensive gene flow in A. narinari. The degree of genetic population structuring in the Indo-Pacific was similar to that found on a global scale. Global FST was 0.63 for cytb and 0.57 for ND4, and global φST values were 0.94 for cytb and 0.82 for ND4. This suggests that the A. narinari complex may be more speciose than the two or three species proposed to date. Further sampling and genetic analyses are likely to uncover the ‘evolutionarily significant’ and ‘management’ units that are critical to determine the susceptibilities of individual populations to regional fishing pressures and to provide advice on management options. Network analyses showed a close genetic relationship between haplotypes from the central Indo-Pacific and South Africa, providing support for a proposed dispersal pathway from the possible centre of origin of the A. narinari species complex in the Indo-Pacific into the Atlantic Ocean.

Lack of population structure in the fiddler crab Uca annulipes along an East African latitudinal gradient: genetic and morphometric evidence

Phylogeographic patterns in Uca annulipes sampled from 30 locations across an East African latitudinal gradient were investigated using mitochondrial DNA cytochrome oxidase I sequences and analysed together with patterns of morphometric differentiation. Four hundred and four specimens along the east African coast were sampled, and 18 haplotypes were encountered. Haplotype and nucleotide diversity values were very low and the phylogenetic analysis did not reveal any clear phylogeographic structure. Furthermore, the analysis of molecular variance and pairwise ΦST values showed no significant spatial population differentiation. Mismatch analyses and tests of neutrality supported the hypothesis that this species has undergone a fairly recent demographic expansion. Our results, therefore, failed to demonstrate significant geographical structure in the pattern of genetic variation, indicating that populations of U. annulipes are capable of extensive gene flow among mangroves along the coast. The genetic structure of this species could be panmictic due to a high amount of gene flow along the geographical gradient in study during the planktonic larval phase, when larvae are carried along stream by the dominant currents. Moreover, the morphometric analysis performed did not reveal differences of shape differentiation according to a geographical pattern, although significant differences among the sampling areas were found.

Variation and genetic structure of Melipona quadrifasciata Lepeletier (Hymenoptera, Apidae) populations based on ISSR pattern.

For a study of diversity and genetic structuring in Melipona quadrifasciata, 61 colonies were collected in eight locations in the state of Minas Gerais, Brazil. By means of PCR analysis, 119 ISSR bands were obtained, 80 (68%) being polymorphic. He and H B were 0.20 and 0.16, respectively. Two large groups were obtained by the UPGMA method, one formed by individuals from Januária, Urucuia, Rio Vermelho and Caeté and the other by individuals from São João Del Rei, Barbacena, Ressaquinha and Cristiano Otoni. The Φst and θB values were 0.65 and 0.58, respectively, thereby indicating high population structuring. UPGMA grouping did not reveal genetic structuring of M. quadrifasciata in function of the tergite stripe pattern. The significant correlation between dissimilarity values and geographic distances (r = 0.3998; p < 0.05) implies possible geographic isolation. The genetic differentiation in population grouping was probably the result of an interruption in gene flow, brought about by geographic barriers between mutually close geographical locations. Our results also demonstrate the potential of ISSR markers in the study of Melipona quadrifasciata population structuring, possibly applicable to the studies of other bee species.

Genetic diversity in Tunisian Crataegus azarolus L. var. aronia L. populations assessed using RAPD markers

• The genetic diversity of nine wild Tunisian Crataegus azarolus var. aronia L. populations from different bioclimates was assessed using RAPD markers.• Eight selected primers generated a total of 105 bands, 81 of which were polymorphic. Shannon’s index (H ′) ranged from 0.222 to 0.278 according to a population with an average of 0.245. The genetic variation within the species (H SP = 0.423) was relatively low. A high differentiation (G ST = 0.421) among populations coupled with a low level of gene flow (N m = 0.472) were observed. The analysis of molecular variance (AMOVA) revealed also significant differentiation among populations (ΦST = 0.371), even at a low scale space. The majority of variation occurred within populations (63.31%). The Mantel test performed on genetic (ΦST ) and geographic distance matrices among population pairs did not reveal an isolation by distance.• Interpretation of Neighbour-joining tree based on Nei’s and Li’s genetic distance among individuals showed distinct population groupings. The UPGMA dendrogram based on ΦST values revealed two population sub-clusters, each including populations from different bioclimates and/or geographic regions.• The low level of genetic diversity and the high genetic structure of populations resulted from genetic drift caused both by habitat fragmentation and the low size of populations.• The high differentiation among populations and the similar low level of diversity within populations suggest that in situ conservation should interest all populations. The ex situ conservation should be based on the collection of seeds rather within than among populations because of the maximum of variation was revealed within populations.

Genetic and morphological differentiation of the mangrove crab Perisesarma guttatum (Brachyura: Sesarmidae) along an East African latitudinal gradient

The genetic structure and morphometric differentiation of mangrove crab Perisesarma guttatum populations were examined among shelf connected locations along a latitudinal gradient on the East African coast. Over 2200 specimens were sampled from 23 mangrove sites for geometric morphometrics analysis. Population genetic analyses of mitochondrial cytochrome c oxidase subunit I (COI) DNA sequences were used to evaluate connectivity among populations. A total of 73 haplotypes were detected, and almost no haplotypes were found in common between two highly supported phylogeographic clades: southern Mozambique (Inhaca Island and Maputo Bay) and a northern clade that included north Mozambique, Tanzania and Kenya. These two clades were identified based on the species' populations pairwise genetic differentiation and geographical location. ΦST values were considerably high between the two clades, indicating the presence of significant population genetic structure between Kenya and South Mozambique. However, each clade was composed of genetically similar populations along the latitudinal gradient, and no significant population structure was found within each clade because the Φst values were not significant. The morphometric analysis corroborated the division into two clades (i.e. Inhaca Island/Maputo Bay and northern populations) and also detected less shape variation among populations that were few kilometres apart. The significant spatial genetic structuring between the southern and the northern populations of P. guttatum along the geographic gradient under study, combined with morphological differences, suggests that these populations may be considered as cryptic species.

Genetic assessment of connectivity in the common reef sponge, Callyspongia vaginalis (Demospongiae: Haplosclerida) reveals high population structure along the Florida reef tract

The genetic population structure of the common branching vase sponge, Callyspongia vaginalis, was determined along the entire length (465 km) of the Florida reef system from Palm Beach to the Dry Tortugas based on sequences of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene. Populations of C. vaginalis were highly structured (overall ΦST = 0.33), in some cases over distances as small as tens of kilometers. However, nonsignificant pairwise ΦST values were also found between a few relatively distant sampling sites suggesting that some long distance larval dispersal may occur via ocean currents or transport in sponge fragments along continuous, shallow coastlines. Indeed, sufficient gene flow appears to occur along the Florida reef tract to obscure a signal of isolation by distance, but not to homogenize COI haplotype frequencies. The strong genetic differentiation among most of the sampling locations suggests that recruitment in this species is largely local source-driven, pointing to the importance of further elucidating general connectivity patterns along the Florida reef tract to guide the spatial scale of management efforts.

Environmental features of deep‐sea habitats linked to the genetic population structure of a crustacean species in the Mediterranean Sea

AbstractThe deep‐sea habitat, from 200 to 2000 m depth, has long been thought as an ecosystem where biotic and abiotic factors vary very little and consequently species are not disturbed by processes and phenomena which could promote fast evolutionary mechanisms. Unfortunately, biological information relating to deep water is limited, especially regarding the population genetics of species inhabiting the Mediterranean Sea, and general patterns cannot be inferred. In this study we report data on the population genetic structure of Aristeus antennatus, a deep‐sea decapod crustacean species which has been widely studied due to its important economic value. We surveyed and examined the variation in a 369‐bp fragment of the mtDNA control region from individuals caught by Spanish and Italian trawlers in eight localities. High levels of mitochondrial control region haplotypic diversity (ranging from 0.884 to 0.989) were observed. AMOVA showed a high level of genetic variation, more within than between populations, and a low but significant ΦST value was recovered. Minimum spanning network did not separate any haplotype group and haplotype distribution does not mirror the geographic origin of the samples. The absence of population substructuring was also observed with a principal coordinates analysis, which uses an individual‐by‐individual comparison. These results revealed extensive gene flow among populations. Information on demographic history based on mismatch analysis revealed an unstable population, showing an alternate pattern of growth and decline. Our results indicated that in the western and central Mediterranean basins A. antennatus is a large panmictic population with a fluctuating abundance. The absence of deep‐sea barriers and adult migration may prevent the structuring of the species into genetically differentiated populations.

Phylogeographical structure in the coastal species Senecio rodriguezii (Asteraceae), a narrowly distributed endemic Mediterranean plant

AbstractAim Our goals were (1) to assess the levels of chloroplast DNA variation in a narrowly distributed plant restricted to continental islands, (2) to ascertain whether a phylogeographical structure is present in plants restricted to coastal linear systems, and (3) to interpret the results in the light of the known palaeogeography of these islands.Location The Eastern Balearic Islands (Majorca and Minorca) in the Western Mediterranean Basin.Methods Sampling included 134 individuals from 28 populations of Senecio rodriguezii covering the entire range of the species. Sequences of the chloroplast genome (trnT–trnL spacer) were obtained and parameters of population genetic diversity and substructure were determined (hsht, Gst). The geographical structure of genetic variation was assessed by an analysis of molecular variance (AMOVA). Additionally, a spatial AMOVA (SAMOVA) was used to identify groups of populations that were geographically homogeneous and maximally differentiated from each other. Finally, a pattern of isolation by distance was assessed by testing the correlation between the matrix of pairwise ΦST values and the matrix of geographical distances between pairs of populations using a Mantel test.Results Seven haplotypes were detected in S. rodriguezii. Only two of them were shared between islands; all of the others were restricted to Majorca (two) or Minorca (three). Overall, we found high levels of genetic diversity and significant geographical structuring of cpDNA markers. Most of the variation detected can be attributed to differences among populations (84.6%), but there was also a significant differentiation between the islands.Main conclusions Our results support the view that the Balearic Islands constitute a reservoir of genetic diversity, not only for widespread Mediterranean taxa, but also for endemic ones. The intraspecific genetic structure found in S. rodriguezii suggests that its population history was dominated by both expansion and contraction events. This has resulted in a species that is highly structured genetically, showing very few shared haplotypes between islands, and a high number of haplotypes restricted to small geographical areas within the islands. Changes in habitat availability and dynamic processes of population fragmentation and connectivity due to repeated cycles of sea‐level changes during the Quaternary are the possible underlying factors that have shaped the cpDNA pool of this endemic species on a regional scale.

Differential impacts of habitat heterogeneity on male and female connectivity in a spatially structured pest system

AbstractIn a previous study, a model of landscape heterogeneity was developed and applied to a spatially structured wild rabbit (Oryctolagus cuniculus) population. That study showed clearly the influence of resource heterogeneity on connectivity levels. The simulation study was based on female movements and used population genetic validation data appropriate for a female study. Most models assume that males and females will exhibit similar patterns, although this has rarely been tested. In the current study we extend the analysis to consider differences between female and male connectivity in the same spatially structured pest system. Amplified fragment length polymorphism (AFLP) markers were screened on the same samples used previously for mtDNA analysis. The mtDNA data were used to validate female results, and AFLP data were used to validate combined male and female results. Connectivity patterns from the two simulations (female, and combined male and female) connectivity patterns showed no association. However, each was concordant with appropriate validation data, showing highly significant associations between pairwise population connectivity and the genetic data. A relative connectivity metric for the combined simulation was regressed against the mean of pairwise ΦST values, with almost 70% of the variation explained by a linear model. Demonstrating differential effects of habitat heterogeneity on male and female connectivity provides further evidence that spatial resource heterogeneity impacts on connectivity. Understanding differences in population connectivity will allow improved predictions of disease spread, local extinctions and recolonizations. Furthermore, modelling such differences in pest systems will allow management plans to be better targeted, for example by strategically introducing diseases for control purposes into populations which exhibit high male connectivity to aid spread, but low female connectivity to inhibit recolonization potential after control.

Genetic Variation and Population Structure in Big Brown Bats (Eptesicus fuscus): Is Female Dispersal Important?

Abstract The prevailing view of the social organization of temperate bats is that maternity colonies represent aggregations of philopatric females connected to other maternity colonies via male-mediated gene flow. However, few studies have examined fine-scale patterns of matrilineal diversity within and between colonies, and clear evidence of strict philopatry generally is lacking. Here we examine patterns of genetic diversity within and among maternity colonies of big brown bats (Eptesicus fuscus) using both microsatellites and mitochondrial sequences. As in other temperate bats, we observed no differentiation among colonies using nuclear microsatellite markers (FST: −0.0001–0.012; 99.5% of variation within populations). Overall, there was significant mitochondrial structure among colonies, but the pattern was complex, with low ΦST values among some populations and high values among others (range: −0.007–0.491). Three groups of colonies were identified in nested analyses of molecular variance, among whic...

Genetic heterogeneity in the Indian stocks of seahorse (Hippocampus kuda and Hippocampus trimaculatus) inferred from mtDNA cytochrome b gene

Genetic stock structure analysis of two seahorse species from the south east and south west coasts of India (37 samples of Hippocampus kuda and 39 samples of Hippocampus trimaculatus from Kollam (Kerala) and Mandapam (Tamil Nadu)) was carried out through sequence variation analysis of a 350 bp cytochrome b fragment of mitochondrial DNA. This was taken up to support the breeding and restocking programme of these species in natural habitats for conservation purpose. The occurrence of strong genetic subdivision among the samples, detected by the analysis of molecular variance (AMOVA), and significant ΦST values indicated that stocks of both the species in the two Indian coasts are distinct. The findings of the present study have important implications for conservation and management of these two species and we recommend stock-specific, breeding assisted sea-ranching programme for H. kuda and H. trimaculatus along the Indian coasts.

Genetic analysis and conservation of endangered medicinal tree species Taxus wallichiana in the Himalayan region

Taxus wallichiana is one of the most important medicinal tree species of the Himalayan region. Leaf and bark of the species yield an important drug called taxol, which is used for treatment of many types of cancer. There is a serious threat to the existence of the species due to over exploitation in its native habitat. Adequate information on the nature and the extent of genetic diversity in this important species is required for developing suitable strategy for its conservation. Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) were used to assess genetic variation in nine natural populations of T. wallichiana from western part of the Himalayan ranges. Both the markers revealed low genetic diversity in these populations. Average heterozygosity for AFLP and RAPD were 0.3715 and 0.3072, respectively. ΦST values derived from molecular variance were 0.0855 and 0.1005 for AFLP and RAPD, respectively, whereas the corresponding GST values were 0.1796 and 0.2140. Most part of the genetic variation was present within the populations. However, between population variation was low but statistically significant, which suggested that the sampled populations might not constitute a single panmictic population. Cluster analysis and Mantel’s correlation revealed that genetic differentiation broadly followed geographic distribution of the populations. T. wallichiana thus urgently needs to be conserved using both in situ and ex situ conservation approaches.

Genetic variation and conservation of the endangered Chinese endemic herb Dendrobium officinale based on SRAP analysis

Dendrobium officinale (Orchidaceae) is used for traditional medicine and is critically endangered in China. To investigate the genetic structure of this species and to offer some advice on conservation strategies, 84 individuals from nine wild populations of D. officinale were analyzed using the method of sequence-related amplified polymorphism. A high level of genetic diversity was detected (PPB = 88.07%, HE = 0.2880) at the species level. However, the genetic diversity at the population level was lower (PPB = 51.68%, HE = 0.1878) in comparison with other species with similar life history characteristics. Based on analysis of molecular variation, there was moderate variation between pairs of populations with ΦST values ranging from 0.1327 to 0.4151 and on average 27.05% of the genetic variation occurred among populations. Two main clusters were shown in UPGMA using TFPGA, which is consistent with the result of principal coordinate analysis using NTSYS. In situ conservation is the first advocated and and ex situ should be proposed at the same time to protect the endangered plant and to preserve germplasm resources.