Effect of landscape features on genetic structure of the goitered gazelle (<Emphasis Type="Italic">Gazella subgutturosa</Emphasis>) in Central Iran

The populations of goitered gazelle suffered significant decline due to natural and anthropogenic factors over the last century. Investigating the effects of barriers on gene flow among the remaining populations is vital for conservation planning. Here we adopted a landscape genetics approach to evaluate the genetic structure of the goitered gazelle in Central Iran and the effects of landscape features on gene flow using 15 polymorphic microsatellite loci. Spatial autocorrelation, isolation by distance (IBD) and isolation by resistance (IBR) models were used to elucidate the effects of landscape features on the genetic structure. Ecological modeling was used to construct landscape permeability and resistance map using 12 ecogeographical variables. Bayesian algorithms revealed three genetically homogeneous groups and restricted dispersal pattern in the six populations. The IBD and spatial autocorrelation revealed a pattern of decreasing relatedness with increasing distance. The distribution of potential habitats was strongly correlated with bioclimatic factors, vegetation type, and elevation. Resistance distances and graph theory were significantly related with variation in genetic structure, suggesting that gazelles are affected by landscape composition. The IBD showed greater impact on genetic structure than IBR. The Mantel and partial Mantel tests indicated low but non-significant effects of anthropogenic barriers on observed genetic structure. We concluded that a combination of geographic distance, landscape resistance, and anthropogenic factors are affecting the genetic structure and gene flow of populations. Future road construction might impede connectivity and gene exchange of populations. Conservation measures on this vulnerable species should consider some isolated population as separate management units.     

Climate change hastens the conservation urgency of an endangered ungulate

Global climate change appears to be one of the main threats to biodiversity in the near future and is already affecting the distribution of many species. Currently threatened species are a special concern while the extent to which they are sensitive to climate change remains uncertain. Przewalski's gazelle (Procapra przewalskii) is classified as endangered and a conservation focus on the Qinghai-Tibetan Plateau. Using measures of species range shift, we explored how the distribution of Przewalski's gazelle may be impacted by projected climate change based on a maximum entropy approach. We also evaluated the uncertainty in the projections of the risks arising from climate change. Modeling predicted the Przewalski's gazelle would be sensitive to future climate change. As the time horizon increased, the strength of effects from climate change increased. Even assuming unlimited dispersal capacity of gazelles, a moderate decrease to complete loss of range was projected by 2080 under different thresholds for transforming the probability prediction to presence/absence data. Current localities of gazelles will undergo a decrease in their occurrence probability. Projections of the impacts of climate change were significantly affected by thresholds and general circulation models. This study suggests climate change clearly poses a severe threat and increases the extinction risk to Przewalski's gazelle. Our findings 1) confirm that endangered endemic species is highly vulnerable to climate change and 2) highlight the fact that forecasting impacts of climate change needs an assessment of the uncertainty. It is extremely important that conservation strategies consider the predicted geographical shifts and be planned with full knowledge of the reliability of projected impacts of climate change.     

Environmental factors affecting population level genetic divergence of the striped field mouse (<Emphasis Type="Italic">Apodemus agrarius</Emphasis>) in South Korea

The cognizing of connectivity among small mammal populations across heterogeneous landscapes is complicated due to complex influences of landscape and anthropogenic factors on gene flow. A landscape genetics approach offers inferences on how landscape features drive population structure. Through a landscape genetics approach, we investigated influences of geographical, environmental, and anthropogenic features on populations of Apodemus agrarius, the striped field mouse, the prime vector of hemorrhagic fever by a landscape genetic approach. We identified landscape features that might affect the population structure of striped field mice by analyzing microsatellite markers of 197 striped field mice from 21 populations throughout South Korea. We developed Maximum-likelihood population effects models based on landscape distances and resistance matrices and pairwise F_ST values for meta-populations of striped field mouse. We also conducted Mantel and partial Mantel tests to investigate geographic patterns of genetic similarities. In Mantel and partial Mantel tests, the F_ST was significantly correlated with all three models of movement; movement cost, Euclidian distance and least-cost distance, although the magnitudes of correlations varied. The 4 top-ranked models included three variables; temperature, precipitation and one human disturbance factor (population). We did not attain a significant effect for anthropogenic factors on genetic similarities among populations in the Korean striped field mouse, but we confirmed a significant association for genetic similarity with climatic features (temperature and precipitation).     

青海湖地区普氏原羚的种群结构

普氏原羚是中国的特有动物。 1986年在青海湖地区仅发现 35 0只普氏原羚 ,分布于鸟岛、湖东 克图和元者 3个种群之中。 1996～ 1998年 7月至 8月 ,我们沿设定的 10条样线对青海湖地区的普氏原羚进行了考察。调查样线总长度为 37 5 5km。观察记录距样线两侧 10 0m以内普氏原羚足迹链和狼足迹链、粪堆和尿迹。同时记录观察样线两侧 6 0 0m以内的普氏原羚个体 ,记录群体大小、性别和年龄 ,然后 ,计算单位样带面积上普氏原羚和狼的密度。 1997年湖东 克图种群雄羚占 2 9%、雌羚占 5 0 %和幼羚占 2 1% ;元者种群雄羚占 2 9%、雌羚占 43%和幼羚占 2 7%。狼捕食是 1997年湖东 克图种群数量下降的主要原因。在湖东 克图沙漠中 ,1996年普氏原羚群体大小为 9 0± 6 9只 (平均数±方差 ) ,密度为 3 19± 3 5 9只 /km2 ,而 1997年为 4 2± 3 9只 /km2 ,密度为 1 14± 1 0 9只 /km2 。 1997年冬季猎狼后 ,湖东 克图种群数量回升到 2 14± 3 13只 /km2 ,幼羚占群体的2 7%。     

Landscape genetics of the blotched tiger salamander (Ambystoma tigrinum melanostictum)

The field of landscape genetics has great potential to identify habitat features that influence population genetic structure. To identify landscape correlates of genetic differentiation in a quantitative fashion, we developed a novel approach using geographical information systems analysis. We present data on blotched tiger salamanders (Ambystoma tigrinum melanostictum) from 10 sites across the northern range of Yellowstone National Park in Montana and Wyoming, USA. We used eight microsatellite loci to analyse population genetic structure. We tested whether landscape variables, including topographical distance, elevation, wetland likelihood, cover type and number of river and stream crossings, were correlated with genetic subdivision (F(ST)). We then compared five hypothetical dispersal routes with a straight-line distance model using two approaches: (i) partial Mantel tests using Akaike's information criterion scores to evaluate model robustness and (ii) the BIOENV procedure, which uses a Spearman rank correlation to determine the combination of environmental variables that best fits the genetic data. Overall, gene flow appears highly restricted among sites, with a global F(ST) of 0.24. While there is a significant isolation-by-distance pattern, incorporating landscape variables substantially improved the fit of the model (from an r2 of 0.3 to 0.8) explaining genetic differentiation. It appears that gene flow follows a straight-line topographic route, with river crossings and open shrub habitat correlated with lower F(ST) and thus, decreased differentiation, while distance and elevation difference appear to increase differentiation. This study demonstrates a general approach that can be used to determine the influence of landscape variables on population genetic structure.     

Genetic diversity in an endangered alpine plant, Eryngium alpinum L. (Apiaceae), inferred from amplified fragment length polymorphism markers

Eryngium alpinum L. is an endangered species found across the European Alps. In order to obtain base-line data for the conservation of this species, we investigated levels of genetic diversity within and among 14 populations from the French Alps. We used the amplified fragment length polymorphism (AFLP) technique with three primer pairs and scored a total of 62 unambiguous, polymorphic markers in 327 individuals. Because AFLP markers are dominant, within-population genetic structure (e.g. FIS) could not be assessed. Analyses based either on the assumption of random-mating or on complete selfing lead to very similar results. Diversity levels within populations were relatively high (mean Nei's expected heterozygosity = 0.198; mean Shannon index = 0.283), and a positive correlation was detected between both genetic diversity measurements and population size (Spearman rank correlation: P = 0. 005 and P = 0.002, respectively). Moreover, FST values and exact tests of differentiation revealed high differentiation among populations (mean pairwise FST = 0.40), which appeared to be independent of geographical distance (nonsignificant Mantel test). Founder events during postglacial colonizations and/or bottlenecks are proposed to explain this high but random genetic differentiation. By contrast, we detected a pattern of isolation by distance within populations and valleys. Predominant local gene flow by pollen or seed is probably responsible for this pattern. Concerning the management of E. alpinum, the high genetic differentiation leads us to recommend the conservation of a maximum number of populations. This study demonstrates that AFLP markers enable a quick and reliable assessment of intraspecific genetic variability in conservation genetics.     

Genetic diversity and differentiation of central European freshwater pearl mussel (Margaritifera margaritifera L.) populations: implications for conservation and management

Despite the fact that mollusc species play an important role in many aquatic ecosystems, little is known about their biodiversity and conservation genetics. Freshwater pearl mussel (Margaritifera margaritifera L.) populations are seriously declining all over Europe and a variety of conservation programs are being established to support the remaining endangered central European populations. In order to provide guidelines for conservation strategies and management programs, we investigated the genetic structure of 24 freshwater pearl mussel populations originating from five major central European drainages including Elbe, Danube, Rhine, Maas and Weser, representing the last and most important populations in this area. We present a nondestructive sampling method of haemolymph for DNA analyses, which is applicable for endangered bivalves. The analyses of nine microsatellite loci with different levels of polymorphism revealed a high degree of fragmented population structure and very different levels of genetic diversity within populations. These patterns can be explained by historical and demographic effects and have been enforced by anthropogenic activities. Even within drainages, distinct conservation units were detected, as revealed from high F(ST) values, private alleles and genetic distance measures. Populations sampled close to contact zones between main drainage systems showed lowest levels of correct assignment to present-day drainage systems. Populations with high priority for conservation should not only be selected by means of census population size and geographical distance to other populations. Instead, detailed genetic analyses are mandatory for revealing differentiation and diversity parameters, which should be combined with ecological criteria for sustainable conservation and recovery programs.     

Natural and anthropogenic determinants of genetic structure in the largest remaining population of the endangered golden-brown mouse lemur, Microcebus ravelobensis

Genetic differentiation between natural populations is best understood as a result of both natural and anthropogenic factors. Genetic studies on large populations still living under relatively undisturbed conditions are extremely valuable to disentangle these influences. The effect of three natural (geographic distance, landscape, dispersal) factors and two anthropogenic factors (road, savannah) on gene flow was analyzed in the largest remaining forest region in the range of the endangered golden-brown mouse lemur in Madagascar. A total of 187 individuals from 12 sites were sampled and genotyped at eight polymorphic microsatellite loci. All sites exhibited similar levels of genetic variation. The level of genetic differentiation was low to moderate with pairwise F(ST) values ranging from -0.002 to 0.12, but most were significant and all sites exhibited high self-assignment rates. A spatial autocorrelation analysis was performed at two geographic scales revealing a pattern of isolation-by-distance and suggesting that no clear differences exist between male and female local dispersal. Two Bayesian approaches revealed that a stretch of savannah represented a significant barrier to movement, whereas the influence of the road on gene flow was less clear. Finally, we found that landscape characteristics, in particular altitude, play a role in the functional connectivity of the sites. The study underlines the importance of studies in relatively undisturbed conditions for the interpretation of population genetics data in fragmented environments. The results are discussed in terms of their conservation relevance for forest-dwelling animals such as most primate species.     

Marine landscapes and population genetic structure of herring (Clupea harengus L.) in the Baltic Sea

Numerically small but statistically significant genetic differentiation has been found in many marine fish species despite very large census population sizes and absence of obvious barriers to migrating individuals. Analyses of morphological traits have previously identified local spawning groups of herring (Clupea harengus L.) in the environmentally heterogeneous Baltic Sea, whereas allozyme markers have not revealed differentiation. We analysed variation at nine microsatellite loci in 24 samples of spring-spawning herring collected at 11 spawning locations throughout the Baltic Sea. Significant temporal differentiation was observed at two locations, which we ascribe to sympatrically spawning but genetically divergent 'spawning waves'. Significant differentiation was also present on a geographical scale, though pairwise F(ST) values were generally low, not exceeding 0.027. Partial Mantel tests showed no isolation by geographical distance, but significant associations were observed between genetic differentiation and environmental parameters (salinity and surface temperature) (0.001 < P < or = 0.099), though these outcomes were driven mainly by populations in the southwestern Baltic Sea, which also exhibits the steepest environmental gradients. Application of a novel method for detecting barriers to gene flow by combining geographical coordinates and genetic differentiation allowed us to identify two zones of lowered gene flow. These zones were concordant with the separation of the Baltic Sea into major basins, with environmental gradients and with differences in migration behaviour. We suggest that similar use of landscape genetics approaches may increase the understanding of the biological significance of genetic differentiation in other marine fishes.     

普氏原羚的分布和种群数量调查

2003 年8 ～9 月,对青海省境内普氏原羚的分布和种群数量进行了专项调查。调查结果表明,普氏原羚现存7 个种群,累计数量为602 只;其中塔勒旋果种群属首次报道。与以往报道相比,目前元者和鸟岛种群数量呈下降趋势;海晏—刚察种群数量增长明显;湖东—克图种群数量有所回升,但仍没有达到20 世纪80 年代中期时的种群数量。普氏原羚种群数量变化与栖息地质量及人为干扰程度有密切相关。本次调查显示,普氏原羚现存栖息地呈不连续的间断分布,随着区域经济开发力度的加大,其栖息地在不断缩减、生存环境质量仍在继续恶化。     

Population structure and landscape genetics in the endangered subterranean rodent Ctenomys porteousi

In order to devise adequate conservation and management strategies for endangered species, it is important to incorporate a reliable understanding of its spatial population structure, detecting the existence of demographic partitions throughout its geographical range and characterizing the distribution of its genetic diversity. Moreover, in species that occupy fragmented habitats it is essential to know how landscape characteristics may affect the genetic connectivity among populations. In this study we use eight microsatellite markers to analyze population structure and gene flow patterns in the complete geographic range of the endangered rodent Ctenomys porteousi. Also, we use landscape genetics approaches to evaluate the effects of landscape configuration on the genetic connectivity among populations. In spite of geographical proximity of the sampling sites (8–27 km between the nearest sites) and the absence of marked barriers to individual movement, strong population structure and low values of gene flow were observed. Genetic differentiation among sampling sites was consistent with a simple model of isolation by distance, where peripheral areas showed higher population differentiation than those sites located in the central area of the species’ distribution. Landscape genetics analysis suggested that habitat fragmentation at regional level has affected the distribution of genetic variation among populations. The distance of sampling sites to areas of the landscape having higher habitat connectivity was the environmental factor most strongly related to population genetic structure. In general, our results indicate strong genetic structure in C. porteousi, even at a small spatial scale, and suggest that habitat fragmentation could increase the population differentiation.     

The effect of landscape features on population genetic structure in Yunnan snub-nosed monkeys (Rhinopithecus bieti) implies an anthropogenic genetic discontinuity

The Tibetan Plateau is one of the top 10 biodiversity hotspots in the world and acts as a modern harbour for many rare species because of its relatively pristine state. In this article, we report a landscape genetic study on the Yunnan snub-nosed monkey ( Rhinopithecus bieti ), a primate endemic to the Tibetan Plateau. DNA was extracted from blood, tissue and fecal samples of 135 wild individuals representing 11 out of 15 extant monkey groups. Ten microsatellite loci were used to characterize patterns of genetic diversity. The most striking feature of the population structure is the presence of five subpopulations with distinct genetic backgrounds and unique spatial regions. The population structure of R. bieti appears to be shaped by anthropogenic landscape features as gene flow between subpopulations is strongly impeded by arable land, highways and human habitation. A partial Mantel test showed that 36.23% ( r  =   0.51, P  =   0.01) of the genetic distance was explained by habitat gaps after controlling for the effect of geographical distance. Only 4.92% of the genetic distance was explained by geographical distance in the partial Mantel test, and no significant correlation was found. Estimation of population structure history indicates that environmental change during the last glacial maximum and human impacts since the Holocene, or a combination of both, have shaped the observed population structure of R. bieti . Increasing human activity on the Plateau, especially that resulting in habitat fragmentation, is becoming an important factor in shaping the genetic structure and evolutionary potential of species inhabiting this key ecosystem.     

Performance of partial statistics in individual‐based landscape genetics

Individual‐based landscape genetic methods have become increasingly popular for quantifying fine‐scale landscape influences on gene flow. One complication for individual‐based methods is that gene flow and landscape variables are often correlated with geography. Partial statistics, particularly Mantel tests, are often employed to control for these inherent correlations by removing the effects of geography while simultaneously correlating measures of genetic differentiation and landscape variables of interest. Concerns about the reliability of Mantel tests prompted this study, in which we use simulated landscapes to evaluate the performance of partial Mantel tests and two ordination methods, distance‐based redundancy analysis (dbRDA) and redundancy analysis (RDA), for detecting isolation by distance (IBD) and isolation by landscape resistance (IBR). Specifically, we described the effects of suitable habitat amount, fragmentation and resistance strength on metrics of accuracy (frequency of correct results, type I/II errors and strength of IBR according to underlying landscape and resistance strength) for each test using realistic individual‐based gene flow simulations. Mantel tests were very effective for detecting IBD, but exhibited higher error rates when detecting IBR. Ordination methods were overall more accurate in detecting IBR, but had high type I errors compared to partial Mantel tests. Thus, no one test outperformed another completely. A combination of statistical tests, for example partial Mantel tests to detect IBD paired with appropriate ordination techniques for IBR detection, provides the best characterization of fine‐scale landscape genetic structure. Realistic simulations of empirical data sets will further increase power to distinguish among putative mechanisms of differentiation.     

Genetic Structure Within and Among Populations of Saruma henryi, an Endangered Plant Endemic to China

The endangered perennial plant Saruma henryi Oliv. is endemic to China and has phylogenetic, ecological, and medicinal value. We used 10 microsatellite (SSR) loci to investigate genetic diversity and differentiation in 16 natural populations. Genetic diversity was high at the species level (H(E) = 0.9427, h = 0.9410, I = 3.0213) and low at the population level (H(E) = 0.4441, h = 0.4307, I = 0.6822). Pronounced genetic differentiation was detected among populations (G(ST) = 0.5428, F(ST) = 0.5524), in line with the limited among-population gene flow (Nm = 0.21). The significant isolation-by-distance pattern revealed by a Mantel test (r = 0.311, P = 0.001) suggested a clear geographic tendency in the distribution of genetic variability. Bayesian assignment and principal coordinates analyses supported the clustering of 16 populations into three groups. The present SSR results were also compared with previously published ISSR results. These results have significant implications for conservation of the species.     

What constitutes a population for the plant parasitic nematode Globodera pallida in its native area (Peru)?

Although numerous species are distributed in discrete populations easily recognised by geographical barriers, continuous populations are a common feature of plants or marine organisms. This is particularly true for soil organisms as their habitat is continuous and their range cannot easily be assessed as they are buried below ground. In the case of organisms for which standard methods such as Capture/Mark/Recapture cannot be used, population genetics provide a straightforward approach to delimitate populations. In this study, we have pursued this topic with a soil-dwelling nematode (Globodera pallida), which parasitises potato roots and is indigenous to South America. Potential barriers to gene flow were identified using the analysis of the F(ST)/(1-F(ST)) ratio against geographical distance and spatial autocorrelation combined with model-based clustering algorithm. Inside regions, neither genetic differentiation nor isolation by distance (IBD) occur among fields less than 50 km distant. We hypothesise that the large amount of gene flow revealed by the absence of genetic structure of this organism could be due to large passive dispersion inside an agronomic area where G. pallida has a continuous distribution and is found at high density. The first evidence of genetic differentiation appeared when a field was separated from others by an area free of farms (where G. pallida is absent or rare). Among regions, a high genetic structure coupled with an IBD pattern occurs as the consequences of the limitations of passive dispersal across deep valleys or high mountains. To our knowledge, this is the first study identifying the spatial limit of a population for a plant nematode parasite.     

Phylogeographical structure, postglacial recolonization and barriers to gene flow in the distinctive Valais chromosome race of the common shrew (Sorex araneus)

Using one male‐inherited and eight biparentally inherited microsatellite markers, we investigate the population genetic structure of the Valais chromosome race of the common shrew (Sorex araneus) in the Central Alps of Europe. Unexpectedly, the Y‐chromosome microsatellite suggests nearly complete absence of male gene flow among populations from the St‐Bernard and Simplon regions (Switzerland). Autosomal markers also show significant genetic structuring among these two geographical areas. Isolation by distance is significant and possible barriers to gene flow exist in the study area. Two different approaches are used to better understand the geographical patterns and the causes of this structuring. Using a principal component analysis for which testing procedure exists, and partial Mantel tests, we show that the St‐Bernard pass does not represent a significant barrier to gene flow although it culminates at 2469 m, close to the highest altitudinal record for this species. Similar results are found for the Simplon pass, indicating that both passes represented potential postglacial recolonization routes into Switzerland from Italian refugia after the last Pleistocene glaciations. In contrast with the weak effect of these mountain passes, the Rhône valley lowlands significantly reduce gene flow in this species. Natural obstacles (the large Rhône river) and unsuitable habitats (dry slopes) are both present in the valley. Moreover, anthropogenic changes to landscape structures are likely to have strongly reduced available habitats for this shrew in the lowlands, thereby promoting genetic differentiation of populations found on opposite sides of the Rhône valley.     

Effects of slope and riparian habitat connectivity on gene flow in an endangered Panamanian frog, Atelopus varius

Aim Understanding how heterogeneous landscapes shape genetic structure not only sheds light on processes involved in population divergence and speciation, but can also guide management strategies to promote and maintain genetic connectivity of populations of endangered species. This study aimed to (1) identify barriers and corridors for gene flow among populations of the endangered frog, Atelopus varius and (2) assess the relative contributions of alternative landscape factors to patterns of genetic variation among these populations in a hypothesis testing framework. Location This study took place in western Panama and included all nine of the remaining known populations of A. varius at the time of study. Methods The influence of landscape variables on gene flow among populations was examined by testing for correlations between alternative landscape‐resistance scenarios and genetic distance. Fifteen alternative hypotheses about the influence of (1) riparian habitat corridors, (2) steep slopes, and (3) climatic suitability on patterns of genetic structure were tested in a causal modelling framework, using Mantel and partial‐Mantel tests, along with an analysis of molecular variation. Results Only the hypothesis attributing resistance to dispersal across steep slopes (genetic isolation by slope distance) was fully supported by the causal modelling approach. However, the analysis of molecular variance and the paths of least‐slope among populations suggest that riparian habitat connectivity may influence genetic structure as well. Main conclusions These results suggest that patterns of genetic variation among A. varius populations are affected by the slope of the landscape such that areas with steep slopes act as barriers to gene flow. In contrast, areas of low slope, such as streams and mountain ridges, appear to be important corridors for gene flow, especially among high elevation populations. These results engender important considerations for the management of this critically endangered species.     

Genetic diversity,population genetic structure and demographic history of Przewalski’s gazelle (<Emphasis Type="Italic">Procapra przewalskii</Emphasis>): implications for conservation

The Przewalski’s gazelle (Procapra przewalskii) is one of the most endangered antelope species in the world. It is endemic to China and is a flagship species in the eastern part of the Qinghai–Tibet plateau. To establish effective conservation measures on this species, genetic information such as genetic structure is needed. However, there has not been a comprehensive genetic assessment on this gazelle using nuclear DNA markers yet. Here, we employed 13 microsatellite loci to investigate genetic diversity, population genetic structure and demographic history of Przewalski’s gazelle using noninvasive samples of 169 wild gazelles collected from nine populations. A total of 76 alleles were detected from the entire samples, mean allele number was 5.85, and overall H _O and H _E were 0.525 and 0.552, respectively. Structure and GENELAND analyses found six genetic groups in the nine populations. Between the inferred genetic groups, significant genetic differentiation and low migration rates were detected. Demographic analyses indicated that Przewalski’s gazelle experienced genetic bottleneck and severe population decline, with the ancestral effective population size reducing to less than one percent. Based on the results of this study, we provide several conservation recommendations for Przewalski’s gazelle, such as six management units, periodic monitoring and special conservation consideration on the Qiejitan population.     

Genetic variation in remnant populations of Dalbergia nigra (Papilionoideae), an endangered tree from the Brazilian Atlantic Forest

BACKGROUND AND AIMS: Dalbergia nigra, known as Brazilian rosewood, is an endangered tree species restricted to the Brazilian Atlantic Forest and has been intensively logged for five centuries due to its high-quality wood. The objective of the present study was to assess the genetic variation and structure in adults and saplings of the species from a large reserve of the Atlantic Forest, the Rio Doce State Park, and from two small surrounding fragments, one better preserved and another with a high degree of anthropogenic disturbance. METHODS: Analyses of genetic variation and structure were conducted by studying allozyme markers. Seven putative enzymatic loci were resolved, five of them being polymorphic. KEY RESULTS: The mean numbers of alleles per locus (A) were 1.93 and 1.73, while the percentages of polymorphic loci (P) were 93 and 73 % for adults and saplings, respectively. Saplings from the fragment with high anthropogenic disturbance exhibited the lowest values of A and P. The fragment that constitutes a conservation area exhibited genetic variation similar to the population from the large reserve. The observed (H(o)) and expected (H(e)) heterozygosities were not significantly different among the three populations. Only sapling populations showed F(ST) values (divergence among populations) significantly different from zero over all studied loci. The fragment with high anthropogenic disturbance exhibited considerable genetic divergence in relation to the above-cited populations. CONCLUSIONS: The evaluated populations displayed mean levels of genetic variation intermediate to those expected for narrow and widespread species. The results suggest that fragments with similar area and geographical distance from a large protected reserve can exhibit different levels of genetic variation, depending on the degree of anthropogenic disturbance. The considerable genetic variation in the protected fragment points to the importance of adequate conservation of small fragments for the preservation of genetic variation in D. nigra.     

Fine scale patterns of migration and gene flow in the endangered mound spring snail, <Emphasis Type="Italic">Fonscochlea accepta</Emphasis> (Mollusca:Hydrobiidae) in arid Australia

Naturally patchy ecosystems are models for other systems currently undergoing anthropogenic habitat fragmentation. Understanding patterns of gene flow in these model systems can help us manage species and ecosystems threatened by human impacts. The mound springs of central Australia represent such a natural model ecosystem, supporting a unique aquatic fauna distributed within an inhospitable arid landscape. Moreover, these springs are being impacted by over extraction of groundwater, providing a unique opportunity to look at dispersal in a patchy habitat that is changing. The present study represents the first fine scale analysis of gene flow under different scenarios of habitat connectivity for the endangered mound spring snail, Fonscochlea accepta. Within a single spring group pairwise estimates of F _ST between springs were very low (ave 0.015) with no association found between genetic distance and a series of geographical distance matrices based on the degree of habitat connectivity among the springs: results implying unstructured dispersal and limited population isolation. However, results from Bayesian assignment tests showed that on average approximately 97% of snails were assigned to their spring of origin. In a preliminary analysis at broader geographic scales (among spring groups) the results from F _ST estimates, Mantel correlation analyses and assignment tests all suggest much stronger and geographically correlated population structuring. While varying results from F-statistics and Bayesian analyses stem from the different information they utilise, together they provide data on contemporary and historical estimates of gene flow and the influence of landscape dynamics on the spatial genetic patterning of the springs.