Fragmentation can increase spatial genetic structure without decreasing pollen‐mediated gene flow in a wind‐pollinated tree
Fragmentation can increase spatial genetic structure without decreasing pollen‐mediated gene flow in a wind‐pollinated tree
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DOI：
10.1111/j.1365-294x.2011.05293.x
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发表时间：
2011-11
影响因子：
4.9
通讯作者：
Rong Wang;S. Compton;Xiao‐Yong Chen
中科院分区：
文献类型：
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作者：
Rong Wang;S. Compton;Xiao‐Yong Chen
破碎化减少了种群规模，增加了栖息地之间的隔离，并可能导致花粉和种子的传播受到限制。鉴于二倍体种子传播比单倍体花粉流对塑造精细尺度空间遗传结构（SGS）的贡献更大，我们测试了即使维持广泛的花粉传播，精细尺度SGS是否对碎片敏感。硬叶槠（Lindley & Paxton）肖特基（壳斗科）是一种风媒授粉和重力种子传播的树，在中国东南部地区进行了研究，该地区的种群因人类活动而不同程度地破碎。在遭受不同破碎程度的地区使用不同年龄级别的树木，我们发现破碎前与破碎后硬叶树亚群之间的遗传多样性没有显着差异。破碎后亚群之间的遗传分化也仅略低于破碎前亚群。在最破碎的栖息地中，破碎前群体的自交率显着高于零，但破碎后群体中则不然。这些结果表明，碎片化并没有减少这些种群中的基因流动，并且花粉流动仍然广泛。然而，在最破碎的栖息地中的破碎后亚群中发现了显着更大的细尺度SGS，但在破碎程度较小的栖息地中却没有发现。 SGS 的这种变化反映了由于物理环境的变化和防止啮齿动物二次种子传播而引起的种子传播受到更多限制。因此，即使面对大量的花粉流，种子传播受到更严格的限制也可能导致 SGS 的增加，这使其成为种群破碎化负面后果的敏感指标。
Fragmentation reduces population sizes, increases isolation between habitats and can result in restricted dispersal of pollen and seeds. Given that diploid seed dispersal contributes more to shaping fine‐scale spatial genetic structure (SGS) than haploid pollen flow, we tested whether fine‐scale SGS can be sensitive to fragmentation even if extensive pollen dispersal is maintained. Castanopsis sclerophylla (Lindley & Paxton) Schottky (Fagaceae), a wind‐pollinated and gravity seed‐dispersed tree, was studied in an area of southeast China where its populations have been fragmented to varying extents by human activity. Using different age classes of trees in areas subject to varying extents of fragmentation, we found no significant difference in genetic diversity between prefragmentation vs. postfragmentation C. sclerophylla subpopulations. Genetic differentiation among postfragmentation subpopulations was also only slightly lower than among prefragmentation subpopulations. In the most fragmented habitat, selfing rates were significantly higher than zero in prefragmentation, but not postfragmentation, cohorts. These results suggest that fragmentation had not decreased gene flow among these populations and that pollen flow remains extensive. However, significantly greater fine‐scale SGS was found in postfragmentation subpopulations in the most fragmented habitat, but not in less fragmented habitats. This alteration in SGS reflected more restricted seed dispersal, induced by changes in the physical environments and the prevention of secondary seed dispersal by rodents. An increase in SGS can therefore result from more restricted seed dispersal, even in the face of extensive pollen flow, making it a sensitive indicator of the negative consequences of population fragmentation.