The Conservation Genetics Of Dysosma (Podophylloideae, Berberidaceae)

Dysosma (Berberidaceae) includes seven perennial herb species endemic to China and its rhizomes is the source of traditional Chinese medicine "Guijiu", so it has important value for the studies of conservation genetics. Despite others have studied the phylogeny of Dysosma and the mating system and/or genetic diversity of D. versipellis, D. pleiantha and D. veitchii deeply, the conservation genetics (e.g. genetic diversity, genetic structure, gene flow and population dynamics) of all of the Dysosma species was lagged behind due to lack of transferable and codominant molecular markers. In this study,18 polymorphic EST-SSRs with transferability in genus were developed from the transcriptome of Dysosma versipellis.15 of them with high polymorphism and low null frequencies were chosen to be used in conservation genetics research of Dysosma.The main results of our study are as follows:(1) Although morphological observation indicated the outcrossing mating system of Dysosma tsayuensis and D. tsaynensis, our study found that the populations were inbreeding (D. aurantiocaulis: FIS=0.400/0.65; D. tsayuensis:FIS=0.408/0.263). It may be because of the small population size or the mating system which may evolved from outcrossing to selfing. In addition, our study demonstrated on a molecular level that the mating system of D. veitchii is selfing, and partial populations of outcrossing species D. difformis, D. versipellis and D. pleiantha were changed into inbreeding population as affected by the sexual reproduction between ramets. (2) The genetic diversity analysis shown that Dysosma species possessed low excepted heterozygosity [ranged from 0.058/0.044(D. aurantiocaulis) to 0.448/0.464(1). difformis)]. Moreover, AMOVA and hierarchical AMOVA displayed that the genetic differentiation were high among populations within species/clusters of D. versipellis, D. pleiantha, D. veitchii and D. difformis (0.469/0.458,0.330/.262,0.424/0.386,0.629/0.666, respectively). Those results indicated that the genetic diversity and differentiation of Dysosma were affected by bottleneck caused by habitat fragmentation. (3) The genetic structure analysis of D. versipellis, D. pleiantha, D. difformis and D. majorensis shown, D. pleiantha, D. difformis and D. majorensis have evolved into a separate species, D. versipellis have defferentiated into three clusters which have equal status with the other Dysosma species on the molecular level. Then a fined genetic structure of Dysosma display that each cluster of D. versipellis, D. pleiantha, D. difformis, D. majorensis and D. veitchii have 18 ESUs totally. (4) Mantel test and Partial mantel test revealed that the differentiation of among populations within D. pleiantha, southern cluster of D. versipellis or D. veitchii were caused by IBD (Isolation by distance) or IBE (Isolation by environment). (5) Cotemporary and historical gene flow and dynamics history analysis revealed that it was climatic fluctuation (10,000-100,000 years ago) and human activities (began in 7000 years ago) that led to the habitat fragmentation of Dysosma species and isolation of gene flow among populations.According to the results above, we put forward the following protection strategy of Dysosma species:conducting independent ex-situ conservation of 20 ESUs [18 +1 (D. aurantiocaulis)+1 (D. tsayuensis)] of Dysosma species, in-situ conservation of populations with big size and genetic diversity, and independent in-situ conservation of populations under different environmental gradient.