Studies On Conservation Genetics Of Endangered Species Litsea Szemaois (Lauraceae)

Litsea szemaois (Lauraceae) is an endemic and endangered species in tropical rain forests of Xishuangbanna, southern Yunnan, SW China. Habitat fragmentation, especially rubber planting, have caused decline of population size of the species. AFLP were used to investigate the genetic diversity and population structure of eight natural populations (103 individuals) and one ex situ population (29 seedlings) of the species.For eight natural populations, three primer combinations of AFLP produced a total of 203 unambiguous and repetitious bands, of which 167 (80.79%) were polymorphic. The results showed that Litsea szemaois exhibited a comparative high genetic diversity: at species level, the value of the average percentage of polymorphic bands (PPB) is 80.79%, expected heterozygosity (h) is 0.1595, Shannon's Information index (I) is 0.2642 and average panmictic hetetozygosity within each population (hs) is 0.1947; at population level, PPB=31.04%,h=0.1025,I=0.1545,hs=0.1589. Most of genetic variation partitioned within populations (77.48%). Genetic differentiation among populations existed and had a low degree: the coefficient of gene differentiation among populations GBstB=0.3403, a Bayesian estimate of F BstB under a random-effects model of population samplingθPBP=0.2164. No correlation was found between geographical and genetic distance, which indicated gene flow may be influenced by complicated local landform or insect pollination and seed-animal dispersal. On the basis of AFLP marker analyses, recent habitat fragmentation may not have led to the loss of genetic diversity or genetic differentiation in the endangered species. The genetic characteristics of Litsea szemaois may be related to geological history of Xishuangbanna region, outbreeding system of the species and complicated local landform.One ex situ population of Litsea szemaois included approximately 60% genetic variation, genetic diversity from the ex situ population was higher than that from in situ populations of the species.More individuals from one or two populations should be selected rather than more populations whenever ex situ or in situ conservation strategies are taken. There was higher genetic variation, a lot of seedlings and young tree at different age in MD population and the habitat of the population was comparatively protected well, so it should be given a priority to protect for in situ conservation. Protecting one ex situ population included 29 seedlings from 6 natural populations should make effect for conservation of Litsea szemaois.