Forest fragmentation effect on the genetic diversity in Southeast Asia

东南亚热带雨林物种多样性丰富，是植物物种的重要栖息地。然而，具有如此高多样性的森林已经被人类活动退化，随后森林变得支离破碎。这种片断化的森林可能会降低物种的遗传多样性，从而导致物种对环境变化的进化能力降低。本研究的目的是阐明马来西亚半岛森林破碎化对麻风藻遗传多样性和基因流的影响。比较了内部群体和边缘群体的遗传多样性、花粉流和遗传距离等参数，并评价了它们之间的差异。两个群体间的基因多样性和等位基因丰富度差异不显著。稀有等位基因数量从种群边缘向种群内部递增，与林缘距离呈正相关，与成虫密度呈负相关。边缘种群的花粉流大多局限在200m以内，但内部种群的花粉流较长。边缘种群和内部种群均表现为随机交配，但遗传分化极显着。这些结果表明，未来边缘种群的遗传多样性可能会下降，因此，我们必须制定适当的保护计划来保护这些破碎的森林。

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.