Forest fragmentation effect on the genetic diversity in Southeast Asia

东南亚热带雨林具有丰富的物种多样性，是植物物种的重要栖息地。然而，具有如此高多样性的森林由于人类活动而减少，随后森林被分割。这种破碎化的森林可能会降低物种的遗传多样性，从而导致对环境变化的进化能力下降。本研究的目的是阐明森林片断化对马来西亚半岛麻风树遗传多样性和基因流的影响。比较了内居群和边缘居群的遗传多样性、花粉流和遗传距离等参数，并对它们之间的差异进行了评价。两个群体的基因多样性和等位基因丰富度差异不显著。而稀有等位基因的数量从边缘到种群内部逐渐增加，且与距林缘的距离呈正相关，与成虫密度呈负相关。边缘种群的花粉流主要集中在200 m以内，而内部种群的花粉流则较长。边缘种群和内部种群均表现为随机交配，但遗传分化极显著。这些结果表明，边缘种群的遗传多样性在未来可能会下降，因此，我们必须制定适当的保护计划，以保护这种破碎的森林。

Tropical rain forests in Southeast Asia have rich species diversity and are important habitats for plant species. However, forests with such high diversity have been declined by human activity and subsequently the forests have been fragmented. Such fragmented forest may reduce the genetic diversity of species and consequently lead to reduction of the evolution ability against environment changes. Our objective in this study is to clarify the effect of forest fragmentation on the genetic diversity and gene flow of Shorea leprosula in Peninsular Malaysia. We have compared the parameters of genetic diversity, pollen flow and genetic distance between inside and marginal populations and evaluated the differences between them. Gene diversity and allelic richness between two populations was not significantly different. But the number of rare alleles was increased from the marginal to inside population and was positively correlated to the distance from the edge of forest and negatively correlated to the density of adult individuals. The pollen flow at marginal population was limited mostly within 200 m but at the inside area was rather longer. Both marginal and inside populations showed random mating but the genetic differentiation between them was highly significant. These results suggest that genetic diversity at marginal population might decrease in the future, and therefore, we have to make a suitable conservation plan to protect such fragmented forests.