板栗和锥栗同域居群的空间遗传结构

Spatial Genetic Structure of A Sympatric Population of Castanea mollissima and Castanea henryi

摘要:

采用微卫星技术研究了板栗(Castanea mollissima)和锥栗(C. henryi)同域分布居群的空间遗传结构, 探讨了它们的遗传变异空间分布特征及其形成机制。结果表明,采用的7个微卫星在两物种中共扩增出173个等位基因,两物种都具有较高的遗传多样性且种间遗传分化水平较低(F_ST=0.051), 但空间自相关分析揭示板栗和锥栗在同域居群中具有不同的空间遗传结构,锥栗在100 m内有空间遗传结构,而板栗没有;同时,基于亲缘关系系数F_ij的Sp统计值也显示锥栗具有比板栗更强的空间遗传结构(板栗的Sp=0.002;锥栗的Sp=0.018)。居群遗传变异的空间结构是其传粉和种子散播及生境共同作用的结果,其中种子的近距离散播和居群密度可能是主要的因素。板栗和锥栗居群在小尺度上空间遗传结构的差异可能反映了它们种子的大小及扩散过程的差异。

Abstract:

The spatial genetic structure (SGS) is an important part of evolutionary ecological and ecological genetic processes in natural populations of plants. The spatial distribution patterns of genetic variation of two closely related sympatric Castanea species, C. mollissima and C. henryi, were investigated using seven microsatellite loci. A total of 173 alleles were detected in the two species. According to the isolation by distance model, Sp-statistics were calculated based on Moran's I spatial autocorrelation coefficient and F_ij kinship coefficient for the two species. The results showed that there were high polymorphism in each species with low genetic differentiation ( F_ST=0.051). However, the two species displayed significant difference of SGS in this sympatric population. Spatial genetic structure was detected in C. henryi up to 100 m, while that was not observed in C. mollissima. Moreover, the Sp-statistic values based on F_ij, were 0.002 for C. mollissima and 0.018 for C. henryi. These results further supported that C. henryi had stronger spatial genetic structure than C. mollissima. The difference of SGS in C. mollissima and C. henryi can be explained by different seed characteristics, as C. mollissima was charactertized by three nuts per cupule while there was only one nuts per cupule for C. henryi. Therefore, the long-distance seed dispersal via gravity and animals was much more favored for C. mollissima than C. henryi, which reduced different SGS between the two species.