极度濒危植物五针白皮松的保护遗传学研究

Conservation Genetics of an Extremely Endangered Pine,Pinus squamata

用随机扩增多态 (RAPD)方法对极度濒危植物五针白皮松 (PinussquamataX .W .Li)的遗传多样性和居群遗传结构进行了研究。 1 4个随机引物共获得 93条RAPD谱带 ,其中6条为多态带 ,多态位点百分率仅为 6 4 5 % ,遗传多样性极低。Shannon指数I和Nei指数h在种内也只有 0 0 2 0和 0 0 30 ,两个亚居群间 (半阴坡亚居群与半阳坡亚居群 )遗传分化程度不高 ,遗传分化系数Gst只有 0 1 1 0 ,与大多数松科植物近似 ,居群每代迁移数为 4 0 32。五针白皮松极低的遗传多样性可能是由于它在演化过程中遭受过严重的灾害 ,造成严重的瓶颈效应 ,丧失其大部分遗传变异。在随后的演化过程中由于遗传漂变、自交衰退等小种群现象 ,导致遗传多样性的进一步丧失。另外 ,阔叶树种对其生存的挤压和人类的干扰也是导致五针白皮松遗传多样性降低的因素之一。

Pinus squamata is an extremely endangered pine from NE Yunnan, China,which was found in one wild population with 32 individuals. We analyzed the genetic aspects that could shed light on the conservation of this species.The genetic structure of two subpopulations was examined by using 14 random amplified polymorphic DNA (RAPD) primers. P squamata has an extremely low level of genetic variation with only 6 45% of the loci assayed being polymorphic,i e.6 loci out of a total of 93 loci.The Shannon Index ( I )and the Nei Index ( h ) of the species are only 0 020 and 0 030,respectively.Comparing the genetic diversity of the two subpopulations,the subpopulation on the south west slope was two fold higher than that on the north east slope.This may be attributed to the more divergent environment on the south west slope than on that of the north east slope.After calculating Nei's G st to estimate the gene differentiation,we found that there was relatively little genetic diversity exist among subpopulations with a G st =0 110. Because of the lack of fossil records and historical geographical distribution data,it was difficult to interpret the extremely low genetic diversity of the species,but we assumed that P squamata could have suffered from severe bottleneck effect during its evolutionary process.The gene drift and inbreeding may further decrease its genetic diversity in the shrinking populations.The weak competitive ability against broad leaved trees and human activities may also have accelerated the decrease of genetic variation.