濒危植物毛柄小勾儿茶片断化居群的遗传多样性

采用扩增片段长度多态性(AFLP)标记对我国特有的濒危植物毛柄小勾儿茶(Berchemiella wilsonii var. pubipetiolata)现存于浙江和安徽的4个片断化居群中的89株个体进行了遗传多样性和遗传结构的研究。结果表明,与其它木本濒危植物相比,毛柄小勾儿茶具有与它们相当的遗传多样性,8对选择扩增引物共扩增出122条清晰的条带,居群的平均多态位点百分率为P_p=26.4%,其中马家河居群最高(29.5%)而湍口居群最低(23.8%),居群的平均基因多样度为H_ep=0.162 8(0.140 5~0.172 4);而在物种水平上的遗传多样性为P_s=36.9%, H_es=0.202 4。居群间的遗传分化系数F_ST=0.193 9,表明居群间有显著的遗传分化,进一步利用AMOVA软件对遗传变异进行等级剖分发现:24.88%的遗传变异存在于地理宗间(浙江地理宗和安徽地理宗),14.71%的遗传变异存在于居群间,60.42%存在于居群内。该研究结果表明,由于人为干扰引起的生境片断化和居群减小导致了毛柄小勾儿茶居群的遗传多样性丧失和遗传分化,并对毛柄小勾儿茶的生存造成潜在威胁。该文还就保育策略进行了讨论。

GENETIC DIVERSITY IN FRAGMENTED POPULATIONS OF BERCHEMIELLA WILSONII VAR. PUBIPETIOLATA , AN ENDANGERED PLANT ENDEMIC TO EASTERN CHINA

Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is an endangered tree species with a narrow distribution in fragmented habitat patches in Tianmu Mountain, Zhejiang Province and Dabie Mountain, Anhui Province, east of China. The habitat has been severely disturbed because of agricultural practices by local residents. Over the past several decades, there has been a decrease in the population number and size. Information on genetic variation and structure is critical for developing successful conservation strategies for this species. The amplified fragment length polymorphisms (AFLPs) were used to evaluate the genetic diversity and population structure of four extant populations of B. wilsonii var. pubipetiolata. A total of 122 unambiguous bands were generated using eight primer combinations of which 45 (36.9%) were polymorphic across all individuals. In comparison with other endangered woody plants, B. wilsonii var. pubipetiolata has similar genetic diversity at the population level (P-p=26.4%, H- ep =0.162 8) and species level (P-s=36.9%, H- es = 0.202 4 ). A relatively high value of F- ST (0.193 9) indicated significant genetic differentiation among populations. Analysis of molecular variance (AMOVA) further revealed that 24.88% of the AFLP variation resided between geographic domes (Zhejiang and Anhui Province), 14.71% among populations and 60.42% within populations. The results of this study suggest that habitat fragmentation and reduction of population size caused by anthropogenic activities have caused genetic erosion and population differentiation in B. wilsonii var. pubipetiolata, which poses a potential threat to the long-term survivability of this species. Genetic information obtained in the present study provides useful baseline data for formulating conservation strategies. Conservation management should include both in situ conservation and ex situ conservation programs and need to be well designed. An ex situ conservation strategy for extensive sampling of all extant populations to maximize genomic representation of the species is recommended.