论文部分内容阅读
濒危植物鹅掌楸(Liriodendron chinense)目前仅零散分布于我国亚热带及越南北部地区,残存居群生境片断化较为严重。研究濒危植物片断化居群的遗传多样性及小尺度空间遗传结构(spatial genetic structure)有助于了解物种的生态进化过程以及制定相关的保育策略。本研究采用13对微卫星引物,对鹅掌楸的1个片断化居群进行了遗传多样性及空间遗传结构的研究,旨在揭示生境片断化条件下鹅掌楸的遗传多样性及基因流状况。研究结果表明:鹅掌楸烂木山居群内不同生境斑块及不同年龄阶段植株的遗传多样性水平差异不显著(P>0.05),居群内存在寨内和山林2个遗传分化明显的亚居群。烂木山居群个体在200 m以内呈现显著的空间遗传结构,而2个亚居群内的个体仅在20 m的距离范围内存在微弱或不显著的空间遗传结构。鹅掌楸的空间遗传结构强度较低(Sp=0.0090),且寨内亚居群的空间遗传结构强度(Sp=0.0067)要高于山林亚居群(Sp=0.0053)。鹅掌楸以异交为主,种子较轻且具翅,借助风力传播,在一定程度上降低了空间遗传结构的强度。此外,居群内个体密度及生境特征也对鹅掌楸的空间遗传结构产生了一定影响。该居群出现显著的杂合子缺失,近交系数(FIS)为0.099(P<0.01),表明生境片断化的遗传效应正逐渐显现。因此,对鹅掌楸的就地保护应注意维护与强化生境的连续性,促进基因交流。迁地保护时,取样距离应不小于20 m,以涵盖足够多的遗传变异。
At present, Liriodendron chinense, an endangered species, is only scattered in the subtropical China and the northern part of Vietnam. The habitat fragmentation of surviving populations is more serious. Studying the genetic diversity of fragmented populations of endangered plants and the spatial genetic structure at small scales can help to understand the ecological evolution of species and formulate relevant conservation strategies. In this study, 13 pairs of microsatellite primers were used to study the genetic diversity and spatial genetic structure of a fragmented population of Liriodendron chinense, in order to reveal the genetic diversity and gene flow of Liriodendron chinense in habitat fragmentation situation. The results showed that there was no significant difference in the genetic diversity between different habitats and different age groups in the Populus tomentosa populations of Populus tomentosa (P> 0.05) Population. The individuals of Rotten wood population showed significant spatial genetic structure within 200 m, while the individuals within two subpopulations showed only slight or insignificant spatial genetic structure only within the distance of 20 m. The spatial genetic structure of Liriodendron chinense was lower (Sp = 0.0090), and the spatial genetic structure of Zarya population was higher (Sp = 0.0067) than that of the subtropical forest (Sp = 0.0053). Liriodendron dominated by cross-breeding, seeds lighter and winged, with the help of wind transmission, to a certain extent, reduced the strength of spatial genetic structure. In addition, the individual density and habitat characteristics in the population also had some impact on the spatial genetic structure of Liriodendron chinense. Significant loss of heterozygotes was observed in this population, with an inbreeding coefficient (FIS) of 0.099 (P <0.01), indicating that the genetic effect of habitat fragmentation is gradually emerging. Therefore, in situ conservation of Liriodendron should pay attention to the continuity of conservation and enhancement of habitats and promote gene exchange. When ex-situ conservation, the sampling distance should not be less than 20 m to cover enough genetic variation.