• Open Access

Fragmentation reduces regional-scale spatial genetic structure in a wind-pollinated tree because genetic barriers are removed

Authors

  • Rong Wang,

    1. Tiantong National Observation Station of Forest Ecosystems, Department of Environmental Sciences, East China Normal University, Shanghai, China
    2. School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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  • Stephen G. Compton,

    1. School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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  • Yi-Su Shi,

    1. Tiantong National Observation Station of Forest Ecosystems, Department of Environmental Sciences, East China Normal University, Shanghai, China
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  • Xiao-Yong Chen

    Corresponding author
    • Tiantong National Observation Station of Forest Ecosystems, Department of Environmental Sciences, East China Normal University, Shanghai, China
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  • This work was supported by the National Natural Science Foundation of China (30970430), the Fundamental Research Funds for the Central Universities (78220028) and “211 Projects” of ECNU to XYC.

Correspondence

Xiao-Yong Chen, Department of Environmental Sciences, East China Normal University, Shanghai 200062, China. Tel/Fax: +86-21-6223-3303; Email: xychen@des.ecnu.edu.cn

Abstract

Gene flow strongly influences the regional genetic structuring of plant populations. Seed and pollen dispersal patterns can respond differently to the increased isolation resulting from habitat fragmentation, with unpredictable consequences for gene flow and population structuring. In a recently fragmented landscape we compared the pre- and post-fragmentation genetic structure of populations of a tree species where pollen and seed dispersal respond differentially to forest fragmentation generated by flooding. Castanopsis sclerophylla is wind-pollinated, with seeds that are dispersed by gravity and rodents. Using microsatellites, we found no significant difference in genetic diversity between pre- and post-fragmentation cohorts. Significant genetic structure was observed in pre-fragmentation cohorts, due to an unknown genetic barrier that had isolated one small population. Among post-fragmentation cohorts this genetic barrier had disappeared and genetic structure was significantly weakened. The strengths of genetic structuring were at a similar level in both cohorts, suggesting that overall gene flow of C. sclerophylla has been unchanged by fragmentation at the regional scale. Fragmentation has blocked seed dispersal among habitats, but this appears to have been compensated for by enhanced pollen dispersal, as indicated by the disappearance of a genetic barrier, probably as a result of increased wind speeds and easier pollen movement over water. Extensive pollen flow can counteract some negative effects of fragmentation and assist the long-term persistence of small remnant populations.

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