RAPD analysis of genetic diversity and population genetic structure of Stipa krylovii reshov. in Inner Mongolia steppe

Random amplified polymorphic DNA (RAPD) analysis was used to characterize the genetic diversity and population genetic structure of Stipa krylovii populations in Inner Mongolia steppe of North China. Thirteen 10-bp oligonucleotide primers, which generated 237 RAPD bands, were used to analyze 90 plants of five populations from three regions, meadow steppe, typical steppe and desert steppe, from the east to the west. The genetic diversity of Stipa krylovii that was revealed by observed number of alleles (na), expected number of alleles (ne), Nei’s diversity index (h), Shannon’s diversity index (H), amplificated loci, polymorphic loci and the percentage of polymorphic loci (PPB) increased from the east to the west. The Pearson’s correlation analysis between genetic diversity parameters and ecological parameters indicated that the genetic diversity of Stipa krylovii was associated with precipitation and cumulative temperature variations along the longitude (humidity were calculated by precipitation and cumulative temperature). Dendrogram based on Jaccard’s genetic distance showed that the individuals from the same population formed a single subgroup. Although most variation (56.85%) was within populations, there was high genetic differentiation among populations of Stipa krylovii, high differentiation within and between regions by AMOVA analysis. Either Nei’s unbiased genetic distance (G _ST) or gene flow (Nm) among pairwise populations was not correlated with geographical distance by Mantel’s test (P > 0.05), suggesting that there was no consistency with the isolation by distance model in these populations. Natural selection may have played a role in affecting the genetic diversity and population structure, but habitat destruction and degradation in northem grassland in China may be the main factor responsible for high genetic differentiation among populations, within and among regions. The text was submitted by the authors in English.     

Genetic differentiation and diversity analysis of medicinal tree Syzygium cumini (Myrtaceae) from ecologically different regions of India

This study represents the agro-ecological zone wise surveys of molecular variation of important medicinal tree Syzygium cumini Linn. (Jamun) which is native to India. It is used world wide in treatment of diabetes. Despite of its diverse medicinal properties no molecular data is available about the pattern of variation in its natural range. Populations of S. cumini in India are located in different habitats which differ from each other with regard to ecological factors. In this study, random amplified polymorphic DNA (RAPD) markers were used to detect inter and intra levels of genetic variations of sixteen S. cumini genotypes collected from three major agro-ecological zones of India. A total of 220 amplification products were scored of which 87.50 % were polymorphic. The level of polymorphism ranged from 47.69 % to 74.87 % polymorphic bands per population and was correlated with population size. Different measures of diversity: Shannon’s index of phenotypic diversity (I) = 0.451 ± 0.230; Nei’s genetic diversity (h) = 0.300 ± 0.172; effective number of alleles per locus (Ne) = 1.51 ± 0.347; total species diversity (Hsp) = 0.315 ± 0.031 and within population diversity (Hpop) = 0.158 ± 0.104 showed high genetic diversity at species level. Coefficient of genetic differentiation (Gst =0.498; Nm = 0.503) revealed significant genetic differentiation among the populations. Most of the genetic variations are contained among the populations. The results of cluster analysis and principal component analysis (PCA) give only little evidence for an ecotypic differentiation of S. cumini populations. Present genetic structure of population suggests ex situ conservation in seed banks in which seeds from at least five populations need to collected and conserved. Secondly, our study provides practical information to herbal drugs manufactures who use Jamun as a raw material.     

Genetic diversity and gene flow estimation in Prosopis cineraria (L.) Druce: A key stone tree species of Indian Thar Desert

Selected amplicon data obtained through our earlier study using ISSR and DAMD markers were utilized for determination of diversity within and among the populations of Prosopis cineraria (L.) accessions collected from different districts of Rajasthan (India). A total of 83 bands were generated from eight ISSR and five DAMD primers of which 79 were found to be polymorphic (95.18%). Nei’s gene diversity (h) ranged between 0.185 and 0.301 with overall diversity of 0.316 while Shannon’s information index (I) values recorded between 0.253 and 0.438 with an average value of 0.243. The gene flow value (1.713) and the diversity among populations (0.226) demonstrated higher genetic variation within the population. It is concluded that P. cineraria is accompanied by high genetic diversity within the population and elevated gene flow showing indications of adaptation to callous and fragile dry conditions of arid environment.     

Genetic variability of Chalara fraxinea, dieback cause of European ash (Fraxinus excelsior L.)

A total of 159 colonies of Chalara fraxinea were isolated between 2005 and 2006 from dying trees of European ash (Fraxinus excelsior L.) aged between 3 and 10 years. They derived from five regions of Poland differing by geographic location and climatic conditions. On the basis of 90 RAMS markers, pathogen intra- and inter-population variability, as well as its dependency on geographic distance and climatic conditions in the regions of strain origin, was analysed. The applied measures of intrapopulation genetic variability (genetic distance, Nei’s unbiased diversity, Shannon’s Information Index and percentage of polymorphic loci) allowed for differentiation of two strain groups: the first deriving from lowlands and the second from uplands and mountainous areas. Strains in lowlands were characterised by smaller number of markers, smaller number of polymorphic loci and smaller intrapopulation genetic variability. Positive and statistically significant correlation was shown between variability of isolates and elevation of regions above sea level. Pair-wise genetic distances between groups of isolates (Nei’s unbiased genetic distance) from particular regions were not significantly correlated with the corresponding geographic distances. On the basis of AMOVA, it was shown that 85% of variability was within-region differences and 2% between-region differences, whereas differences between lowlands and uplands were 13%. Principal Components Analysis (PCA) for the investigated regions confirmed the results from Nei’s genetic distance matrix.     

Remnants fragments preserve genetic diversity of the old forest lichen <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> in a fragmented Mediterranean mountain forest

Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m²) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei’s) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.     

Dispersal ecology of the endangered woodland lichen Lobaria pulmonaria in managed hemiboreal forest landscape

Changes in the forest management practices have strongly influenced the distribution of species inhabiting old-growth forests. The epiphytic woodland lichen Lobaria pulmonaria is frequently used as a model species to study the factors affecting the population biology of lichens. We sampled 252 L. pulmonaria individuals from 12 populations representing three woodland types differing in their ecological continuity and management intensity in Estonia. We used eight mycobiont-specific microsatellite loci to quantify genetic diversity among the populations. We calculated the Sørensen distance to estimate genetic dissimilarity among individuals within populations. We revealed that L. pulmonaria populations have significantly higher genetic diversity in old-growth forests than in managed forests and wooded meadows. We detected a significant woodland-type-specific pattern of genetic dissimilarity among neighbouring L. pulmonaria individuals, which suggests that in wooded meadows and managed forests dominating is vegetative reproduction. The vegetative dispersal distance between the host trees of L. pulmonaria was found to be only 15–30 m. Genetic dissimilarity among individuals was also dependent on tree species and trunk diameter. Lobaria pulmonaria populations in managed forests included less juveniles compared to old-growth forests and wooded meadows, indicating that forest management influences life stage structure within populations. We conclude that as intensive stand management reduces the genetic diversity of threatened species in woodland habitats, particular attention should be paid to the preservation of remnant populations in old-growth habitats. Within managed habitats, conservation management should target on maintenance of the stand’s structural diversity and availability of potential host trees.     

Low genetic differentiation between apotheciate Usnea florida and sorediate Usnea subfloridana (Parmeliaceae,Ascomycota) based on microsatellite data

Accurate species delimitation has a pivotal role in conservation biology, and it is especially important for threatened species where decisions have political and economic consequences. Finding and applying appropriate character sets and analytical tools to resolve interspecific relationships remains challenging in lichenized fungi. The main aim of our study was to re-assess the species boundaries between Usnea subfloridana and Usnea florida, which have been phylogenetically indistinguishable until now, but are different in reproductive mode and ecological preferences, using fungal-specific simple sequence repeats (SSR), i.e. microsatellite markers. Bayesian clustering analysis, discriminant analysis of principal components (DAPC), minimal spanning network (MSN), and principal component analysis (PCA) failed to separate U. florida and U. subfloridana populations. However, a low significant differentiation between the two taxa was observed across all populations according to AMOVA results. Also, analysis of shared haplotypes and statistical difference in clonal diversity (M) supported the present-day isolation between the apotheciate U. florida and predominantly sorediate U. subfloridana. Our results do not provide a clear support either for the separation of species in this pair or the synonymization of U. florida and U. subfloridana. We suggest that genome-wide data could help resolve the taxonomic question in this species pair.     

Genetic Variability and Population Structure of the Mushroom Pleurotus eryngii var. tuoliensis

The genetic diversity of 123 wild strains of Pleurotus eryngii var. tuoliensis, which were collected from nine geographical locations in Yumin, Tuoli, and Qinghe counties in the Xinjiang Autonomous Region of China, was analysed using two molecular marker systems (inter-simple sequence repeat and start codon targeted). At the variety level, the percentage of polymorphic loci and Nei’s gene diversity index for P. eryngii var. tuoliensis was 96.32% and 0.238, respectively. At the population level, Nei’s gene diversity index ranged from 0.149 to 0.218 with an average of 0.186, and Shannon''s information index ranged from 0.213 to 0.339 with an average of 0.284. These results revealed the abundant genetic variability in the wild resources of P. eryngii var. tuoliensis. Nei’s gene diversity analysis indicated that the genetic variance was mainly found within individual geographical populations, and the analysis of molecular variance revealed low but significant genetic differentiation among local and regional populations. The limited gene flow (Nm = 1.794) was inferred as a major reason for the extent of genetic differentiation of P. eryngii var. tuoliensis. The results of Mantel tests showed that the genetic distance among geographical populations of P. eryngii var. tuoliensis was positively correlated with the geographical distance and the longitudinal distances (r_Go = 0.789 and r_Ln = 0.873, respectively), which indicates that geographical isolation is an important factor for the observed genetic differentiation. Nine geographical populations of P. eryngii var. tuoliensis were divided into three groups according to their geographical origins, which revealed that the genetic diversity was closely related to the geographical distribution of this wild fungus.     

Genetic variation and phylogeographic history of <Emphasis Type="Italic">Picea likiangensis</Emphasis> revealed by RAPD markers

Repeated cycles of retreat and recolonization during the Quaternary ice ages are thought to have greatly influenced current species distributions and their genetic diversity. It remains unclear how this climatic oscillation has affected the distribution of genetic diversity between populations of wind-pollinated conifers in the Qinghai-Tibetan region. In this study, we investigated the within-species genetic diversity and phylogenetic relationships of Picea likiangensis, a dominant forest species in this region using polymorphic DNA (RAPD) markers. Our results suggest that this species has high overall genetic diversity, with 85.42% of loci being polymorphic and an average expected heterozygosity (H _E) of 0.239. However, there were relatively low levels of polymorphism at population levels and the differences between populations were not significant, with percentages of polymorphic bands (PPB) ranging from 46.88 to 69.76%, Nei’s gene diversity (H _E) from 0.179 to 0.289 and Shannon’s indices (Hpop) from 0.267 to 0.421. In accordance with our proposed hypothesis, a high level of genetic differentiation among populations was detected based on Nei’s genetic diversity (G _ST = 0.256) and AMOVA analysis (Phi _st = 0.236). Gene flow between populations was found to be limited (Nm = 1.4532) and far lower than reported for other conifer species with wide distribution ranges from other regions. No clusters corresponding to three morphological varieties found in the south, north and west, respectively, were detected in either UPGMA or PCO analyses. Our results suggest that this species may have had different refugia during the glacial stages in the southern region and that the northern variety may have multiple origins from these different refugia.     

Epiphytic and epixylic lichen species diversity in Estonian natural forests

The epiphytic and epixylic lichen flora of natural forests was recorded in different parts of Estonia. Altogether 232 taxa of lichens, lichenicolous fungi, or non-lichenized fungi were recorded, 10 of them listed in the Estonian Red Data Book. We found regional differences in lichen species composition and diversity caused by differences in the forest types. The tree-species-rich boreo-nemoral forests had the most diverse lichen flora, while the boreal forest dominated by coniferous trees or birch had the lowest diversity. The stand age proved to be significant in regard to the number of lichen species in a forest. The most remarkable effect on the diversity of forest lichen species was caused by the presence of Populus tremula. Aspen had the highest number of lichen species on the basal trunk and twigs, and also the highest number of host-specific lichen species.     

Genetic diversity and population structure of a protected species: Polygala tenuifolia Willd

Polygala tenuifolia Willd. is an important protected species used in traditional Chinese medicine. In the present study, amplified fragment length polymorphism (AFLP) markers were employed to characterize the genetic diversity in wild and cultivated P. tenuifolia populations. Twelve primer combinations of AFLP produced 310 unambiguous and repetitious bands. Among these bands, 261 (84.2%) were polymorphic. The genetic diversity was high at the species level: percentage of polymorphic loci (PPL) = 84.2%, Nei's gene diversity (h) = 0.3296 and Shannon's information index (I) = 0.4822. Between the two populations, the genetic differentiation of 0.1250 was low and the gene flow was relatively high, at 3.4989. The wild population (PPL = 81.9%, h = 0.3154, I = 0.4635) showed a higher genetic diversity level than the cultivated population (PPL = 63.9%, h = 0.2507, I = 0.3688). The results suggest that the major factors threatening the persistence of P. tenuifolia resources are ecological and human factors rather than genetic. These results will assist with the design of conservation and management programs, such as in natural habitat conservation, setting the excavation time interval for resource regeneration and the substitution of cultivated for wild plants.     

Using genetic diversity information to establish core collections of Stylosanthes capitata and Stylosanthes macrocephala

Stylosanthes species are important forage legumes in tropical and subtropical areas. S. macrocephala and S. capitata germplasm collections that consist of 134 and 192 accessions, respectively, are maintained at the Brazilian Agricultural Research Corporation Cerrados (Embrapa-Cerrados). Polymorphic microsatellite markers were used to assess genetic diversity and population structure with the aim to assemble a core collection. The mean values of H_O and H_E for S. macrocephala were 0.08 and 0.36, respectively, whereas the means for S. capitata were 0.48 and 0.50, respectively. Roger’s genetic distance varied from 0 to 0.83 for S. macrocephala and from 0 to 0.85 for S. capitata. Analysis with STRUCTURE software distinguished five groups among the S. macrocephala accessions and four groups among those of S. capitata. Nei’s genetic diversity was 27% in S. macrocephala and 11% in S. capitata. Core collections were assembled for both species. For S. macrocephala, all of the allelic diversity was represented by 23 accessions, whereas only 13 accessions were necessary to represent all allelic diversity for S. capitata. The data presented herein evidence the population structure present in the Embrapa-Cerrados germplasm collections of S. macrocephala and S. capitata, which may be useful for breeding programs and germplasm conservation.     

ISSR primer screening and preliminary evaluation of genetic diversity in wild populations of Gycyrrhiza uralensis

Fourteen efficient inter-simple sequence repeat (ISSR) primers were screened and optimized for detecting the genetic diversity in wild populations of Glycyrrhiza uralensis Fisch. By using these primers, 249 polymorphic bands out of a total of 270 (92.2 %) were generated from 70 individuals of 4 wild G. uralensis populations sampled from Inner Mongolia Province of China. Nei’s gene diversity (h) and Shannon index (I) calculated from the data matrix of the ISSR phenotypes revealed a high level of genetic diversity with h = 0.268 and I = 0.415 within this plant. Analysis of molecular variation (AMOVA) showed that most of the genetic variation (81 %) occurred within the populations, whereas the variance among populations was only 19 %. The UPGMA tree based on Nei’s unbiased genetic diversity illustrated that populations from Bulage and Bayanwusu were genetically close related, while the population from Shanghaimiao was found to be the most diverse from the other three. The high genetic diversity implies that the wild resources of this species could be restored soon if an appropriate and efficient protection strategy was employed. Our results also provided an optimized method for evaluating genetic diversity of G. uralensis using ISSR markers which was useful for further investigation.     

Genetic analysis of two Portuguese populations of <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> by RAPD profiling

The clam Ruditapes decussatus is commercially important in the south of Portugal. The random amplified polymorphic DNA (RAPD) technique was applied to assess the genetic diversity and population structure of two Portuguese populations occurring in the Ria Formosa (Faro) and the Ria de Alvor, respectively. Twenty-five individuals of each population were investigated by RAPD profiles. Genetic diversity within populations, measured by the percentage of polymorphic loci (%P), varied between 68.57% (Alvor) and 73.88% (Faro). Shannon’s information index (H) and Nei’s gene diversity (h) were 0.281 and 0.176, respectively, for the Alvor population and 0.356 and 0.234 for the Faro population. Overall, genetic variation within R. decussatus populations was high. The total genetic diversity (H _T) was explained by a low variation between populations (G _ST = 0.145), which is consistent with high gene flow (N _m = 2.9). The analysis of molecular variance (AMOVA) showed that 65% of variability is within populations and 35% between populations (Φ_PT = 0.345; P ≥ 0.001). The value of Nei’s genetic distance was 0.0881, showing a low degree of population genetic distance, despite the different geographic origin. This is the first study on the population genetics of R. decussatus by RAPD technique. The results may be useful for restocking programs and aquaculture.     

Genetic Structure of Rhizobium leguminosarum biovar trifolii and viciae Populations Found in Two Oregon Soils under Different Plant Communities

An investigation was carried out to determine the genetic structure in soil populations of Rhizobium leguminosarum bv. trifolii and viciae at each of two Oregon sites (A and C) that were 1 km apart. Although the soils were similar, the plant communities were quite different because grazing by domestic animals had been allowed (site A) or prevented (site C). Analysis of allelic variation at 13 enzyme-encoding loci by multilocus enzyme electrophoresis delineated 202 chromosomal types (ETs) among a total of 456 isolates representing two populations of R. leguminosarum bv. trifolii (AT and CT) and two populations of R. leguminosarum bv. viciae (AV and CV). Regardless of their site of origin or biovar affiliation, isolates of the same ET were confirmed to be more closely related to each other than to isolates of other ETs by repetitive extragenic palindromic and enterobacterial repetitive intergeneric consensus sequences and the PCR technique. Despite the wide range in densities of the Rhizobium populations (<10² to >10⁵/g of soil), their overall genetic diversities were similar (mean genetic diversity, 0.45 to 0.51), indicating that low-density populations of soil-borne bacterial species are not necessarily of little genetic diversity. Linkage disequilibrium analysis revealed significant multilocus structure (nonrandom associations of alleles) within each of the four populations. From a combination of cluster and linkage disequilibrium analyses, a total of eight distinct groups of ETs were defined in the four populations. Two groups (I and III) contributed significant numbers of ETs and isolates to each population. The two populations of R. leguminosarum bv. viciae (AV and CV) exhibited similar genetic structures despite existing at different densities, in different plant communities, and in the presence (CV) or absence (AV) of their local Vicia hosts. In contrast, total linkage disequilibrium was partitioned differently in two biovar populations occupying the same soil (AV and AT), with disequilibrium in the latter being due entirely to the presence of group V.     

Allozyme variations in six natural populations of scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis>) in Turkey

Genetic variation in six natural populations of Scots pine (Pinus sylvestris L.) was determined with isoenzyme analyses. For this purpose, haploid female gametophytes of seeds and horizontal starch gel electrophoresis technique were used. A total of 17 loci and 58 alleles were observed in studying 10 enzyme systems. The average proportion of polymorphic loci for populations ranged from 58.8% to 70.6%. The average number of alleles per locus per population was 2.65. The mean estimated expected heterozygosity (He) of populations was 0.294. A rather high proportion of genetic diversity (96.4%) was due to within-population variation and the remaining (3.6%) was due to variation among populations. The level of gene flow (N_em) was found to be 6.69 per generation. Nei’s genetic distance coefficient ranged from 0.006 to 0.027 (mean 0.017) among all possible population pairs. The mean value of Nei’s genetic distance is similar to the values reported for other European Scots pine populations. The low mean value of Nei’s genetic distance among populations is enough to explain low interpopulation variation. According to genetic variation parameters, three out of six populations (Akdagmadeni-Yozgat, Refahiye-Erzincan and Vezirkopru-Samsun) appear to be preferable populations for genetic conservation and forest tree breeding programs.     

Population Genetics and the Effects of a Severe Bottleneck in an Ex Situ Population of Critically Endangered Hawaiian Tree Snails

As wild populations decline, ex situ propagation provides a potential bank of genetic diversity and a hedge against extinction. These programs are unlikely to succeed if captive populations do not recover from the severe bottleneck imposed when they are founded with a limited number of individuals from remnant populations. In small captive populations allelic richness may be lost due to genetic drift, leading to a decline in fitness. Wild populations of the Hawaiian tree snail Achatinella lila, a hermaphroditic snail with a long life history, have declined precipitously due to introduced predators and other human impacts. A captive population initially thrived after its founding with seven snails, exceeding 600 captive individuals in 2009, but drastically declined in the last five years. Measures of fitness were examined from 2,018 captive snails that died between 1998 and 2012, and compared with genotypic data for six microsatellite loci from a subset of these deceased snails (N = 335), as well as live captive snails (N = 198) and wild snails (N = 92). Surprisingly, the inbreeding coefficient (F_is) declined over time in the captive population, and is now approaching values observed in the 2013 wild population, despite a significant decrease in allelic richness. However, adult annual survival and fecundity significantly declined in the second generation. These measures of fitness were positively correlated with heterozygosity. Snails with higher measures of heterozygosity had more offspring, and third generation offspring with higher measures of heterozygosity were more likely to reach maturity. These results highlight the importance of maintaining genetic diversity in captive populations, particularly those initiated with a small number of individuals from wild remnant populations. Genetic rescue may allow for an increase in genetic diversity in the captive population, as measures of heterozygosity and rarified allelic richness were higher in wild tree snails.     

Genetic diversity of Stipa grandis P.Smirn populations across the species’ range in the Inner Mongolia Plateau of China

In order to investigate the genetic diversity of dominant species under the background of climate change and grassland utilization in the Inner Mongolia Plateau of China, we sampled seven Stipa grandis populations along an increasing aridity gradient in the present study. The Nei’s gene diversity of populations (He) was estimated to be 0.15 and the percentage of polymorphic loci (PPL) was 49.28%. The genetic differentiation among populations (Φ_ST) was 0.2431. There was a significant relationship between genetic distance and geographic distance among the S. grandis populations by Mantel's test. The genetic diversity was significantly correlated with longitude and annual mean precipitation, which suggested that a combination of climatic factors affected the genetic diversity. The populations in the marginal habitat should be paid more attention because of their low genetic diversity and its significance for conservation of the whole species.     

Genetic variability, population size and reproduction potential in Ligularia sibirica (L.) populations in Estonia

Ligularia sibirica (L.) Cass. (Asteraceae) is a EU Habitats Directive Annex II plant species that has suffered a lot from human-caused major changes in quality and availability of habitats in Estonia. The aim of this study was to find out if the observed decline in population size is reflected in the amount of genetic variation and fertility in remnant populations of this species. AFLP technique was used for that purpose. Genetic diversity within populations was assessed as the percentage of polymorphic loci in a given population and average gene diversity over loci. The degree of genetic differentiation among populations and genetic differentiation between pairs of populations was estimated. The amount of viable seeds per flower stem was compared among populations and between years (2007 and 2008). Average genetic diversity over loci and proportion of polymorphic loci in L. sibirica populations were significantly correlated with population size, suggesting the action of genetic drift and/or inbreeding. No correlation was found between genetic and geographic distances. Natural barriers like forests may have been efficiently preventing seed migration even between geographically closer populations. Results of this study suggest that genetic erosion could be partially responsible for the lower fitness in smaller populations of this species.     

Genetic variability and differentiation of <Emphasis Type="Italic">Caragana microphylla</Emphasis> populations as revealed by RAPD markers

Genetic variability in random amplified polymorphic DNA (RAPD) was studied in 90 individuals of Caragana microphylla, an outcrossing perennial shrub species, from five natural populations sampled in Inner Mongolia steppe of China on a small scale. Nineteen selected primers were used to amplify DNA samples, and totally 225 bands were detected. The percentage of polymorphic bands within populations ranged form 58.22% to 63.56%, with an average of 60% at the population level and 71.11% at the species level, indicating relatively high genetic variations in C. microphylla species. Shannon’s information index (l) and Nei’s gene diversity (h) showed the similar trend with each other. According to the analysis of Nei’s gene diversity, the percentage of genetic variation among populations was 7.13%, indicating a low level of genetic differentiation among populations. There existed a strong gene flow (N _m = 3.26) among populations. Although AMOVA analysis also revealed most variation was within populations (Φ_ST = 4.1%), a significant proportion was observed among populations (P < 0.001) in the present study, suggesting genetic differentiation occurred among populations at a certain extent. Based on Mantel’s tests and the results of previous studies, the genetic structure pattern of C. microphylla accorded with the isolation-by-distance model on a very large scale, however, on a small scale, the significant genetic differentiation among populations might be enhanced by the micro-environmental divergence among the sampling sites, rather than by geographic factors. Analysis of the genetic variations of C. microphylla populations provided useful information for the adaptive strategy of Caragana species.