Genetic Diversity And Differentiation Of The Endangered Plant Saruma Henryi Oliv. (Aristolochiaceae)

Conservation of endangered species has become a major concern for biologists and legislatorsbecause of its ecological, educational, historical, recreational, and scientific values. Since genetic diversity in natural populations can significantly affect the long-term survival and evolution of species or populations in changing environments, any conservation effort should aim to preserve maximum genetic diversity within the target gene pool. Thus, scientific assessment of its levels and patterns will contribute substaintially to the formulation of effective conservation strategies for endangered species, and can only be addressed by detailed population genetic analysis.Saruma henryi Oliv., the only representative of the monotypic genus Saruma Oliv. (Aristolochiaceae), is a perennial herb endemic to China. This species has received considerable attention for its phylogenetic, ecological and medicinal significances. However, due to anthropogenic activities (e.g. habitat destruction and over-exploitation) and its unique biological traits (e.g. low flowering rate and low seed setting/germination rates under natural conditions), its habitats have been severely deteriorated and fragmented, and its natural populations have shrunk to alarming small sizes thus in need of urgent protection.However, previous studies of S. henryi have been mainly focused upon its biological traits, To better reveal its real geneic diversity and structure,14 polymorphic microsatellite loci were isolated and characterized from an AC and GA-enriched genomic library of S. henryi. The average allele number of these microsatellites was 7.07 per locus, ranging from 5 to 8. The observed and expected heterozygosity at population level were 0.4762-0.8000 and 0.6281-0.8532, respectively. These polymorphic markers provide useful tools for the study of genetic structure and conservation management of S. henryi.The study on the genetic diversity and differentiation of S. henryi involve 283 individuals from16 natural populations. High genetic diversity was revealed at both population (HE= 0.4441, h=0.4307;I=0.6822) and species (HE=0.9427, h=0.9410;I=3.0213) levels based on the study of 6 genomic SSRs and 4 ESTs derived SSRs, probably owning to its long evolutionary history and widely geographic distribution. AMOWA analysis indicate marked genetic differentiation among populations (GST=0.5428;FST=0.5524), in line with the limited among-population gene flow (Nm= 0.21). This may be explained by its unique inbreeding dominant mating system, genetic drift, demographic fluctuations and geographic isolation. Both Bayesian cluster analysis and Principal Coordinates Analysis (PCoA) supported the clustering of 16 populations into three distinct groups which corresponded to the tree independent geographic regions. Furthermore, Mantel test revealed a significant correlation between genetic and geographic distances among populations (r=0.311, P=0.001), indicating the role of geographic isolation in shaping its present population genetic structure. These results have important implications for its conservation. We suggest the maintenance of effective population sizes and reduction of human disturbance should be given priorities in conservation of S. henryi.