Data from: Does long distance pollen dispersal preclude inbreeding in tropical trees? Fragmentation genetics of Dysoxylum malabaricum in an agro-forest landscape

Tropical trees often display long distance pollen dispersal, even in highly fragmented landscapes. Understanding how patterns of spatial isolation influence gene flow and interact with background patterns of fine scale spatial genetic structure are critical for evaluating the genetic consequences of habitat fragmentation. In the endangered tropical timber tree Dysoxylum malabaricum (Meliaceae) we apply eleven microsatellite markers with paternity and parentage analysis to directly estimate contemporary gene flow across a large area (216 km2) in a highly fragmented agro-forest landscape. A comparison of genetic diversity and genetic structure in adult and juvenile life stages indicates an increase of differentiation and fine-scale spatial genetic structure (FSGS) over time. Paternity analysis and parentage analysis demonstrate high genetic connectivity across the landscape by pollen dispersal. A comparison between mother trees in forest patches with low and high densities of adult trees shows that the frequency of short distance mating increases, as does average kinship among mates in low density stands. We interpret this as an early warning sign of potentially negative genetic consequences of forest fragmentation. Single isolated trees, in contrast, frequently receive heterogeneous pollen from distances exceeding five kilometres. We discuss the processes leading to the observed patterns of gene flow and the implications of this for conservation management of D. malabaricum and tropical trees more generally.

热带树木即便在高度破碎化的景观中，也往往展现出长距离花粉扩散现象。阐明空间隔离格局如何影响基因流，并与精细尺度空间遗传结构的本底格局相互作用，对于评估生境破碎化的遗传效应至关重要。本研究以濒危热带用材树种马拉巴樫木（Dysoxylum malabaricum，楝科Meliaceae）为对象，采用11个微卫星标记结合父本分析与亲权分析，直接估算了高度破碎化农林景观中216 km²大范围区域内的当代基因流。通过对比成体与幼体生命阶段的遗传多样性与遗传结构，研究发现随时间推移，种群分化与精细尺度空间遗传结构（fine-scale spatial genetic structure, FSGS）均有所增强。父本分析与亲权分析结果表明，花粉扩散使该景观整体保持了较高的遗传连通性。通过对比成年树木密度高低不同的林块中的母树，研究发现低密度林分中短距离交配的频率提升，配偶间的平均亲缘关系也随之增强。我们认为这一现象可作为森林破碎化潜在负面遗传效应的早期预警信号。与之相反，孤立单株树木往往接收来自5公里以外的异质花粉。本研究还探讨了驱动观测到的基因流格局的潜在过程，以及该结果对马拉巴樫木（D. malabaricum）乃至热带树木整体保护管理的启示。