A population genetic study on genetic diversity and evolutionary characteristics of Dipterocarpacea in tropical rain forests

为了阐明遗传多样性与热带雨林重要组成部分亚洲龙心科树木的物种多样性之间的关系，我们估计了该科物种之间和物种内部的DNA差异。首先，我们通过对叶绿体DNA进行测序来确定家族内属间的关系。亚洲科成员被划分为两个类群，Shorea属被发现包括一些其他属。接下来，我们用直接测序的方法确定了Shorea、s .麻风、S.acuminata、S.curtisii和S.parvifolia四种植物之间和内部的遗传多样性。虽然在叶绿体DNA区域未检测到任何变异，但在GapC（核）基因部分位点的核苷酸多样性在0.00 12 ~ 0.0029之间。种间差异在0.00781 ~ 0.01621之间。自交率估计在0.39 ~ 0.67之间。为了理解序列数据与选择的进化意义，我们从理论上分析了近中性突变模型。首先，在该模型下，种群规模的变化会增加分散指数（衡量进化速率变异性的指标）。其次，在多位点近中性模型的假设下，研究了使用Tajimas检验和MK检验等中立性检验检测选择的能力。分析表明，区分替代和沉默变异对检测这类选择具有重要意义。我们无法从我们的GapC数据中检测到选择，但这可能是由于该基因的替换变异非常小。我们需要调查更多的基因区域来阐明遗传多样性及其对该科物种多样性的意义

In order to clarify how genetic diversity relates to species diversity found in Asian Dipterocarpaceae trees that comprise important components of tropical rain forests, we estimated DNA variation between and within species in the family. First, we determined the relationships among genera within the family by sequencing chioroplast DNA.The Asian family members were shown to be divided into two groups and the genus Shorea was found to include a few other genera. Next we determined genetic diversity between and within four species in Shorea, S.leprosula, S.acuminata, S.curtisii and S.parvifolia by direct sequencing. Although we could not detect any variation in a chloroplast DNA region, the nucleotide diversity in the partial GapC (nuclear) gene was found to be between 0.00 12 and 0.0029 per site in the four species. The divergence between species was between 0.00781 and 0.01621 . The selfing rate was estimated to be between 0.39 and 0.67.To understand evolutionary implications of sequence data in relation to selection, we analyzed the nearly neutral mutation model theoretically. First, changes of population size were shown to increase the dispersion index, an index measuring variability of evolutionary rates, under this model. Next, the powers of detecting selection using several tests of the neutrality including Tajimas test and the MK test were investigated assuming a multisite nearly neutral model. The analysis showed the importance of discriminating replacement and silent variation for detecting this type of selection. We could not detect selection from our GapC data but this may be due to very little replacement variation in this gene. We need to survey more gene regions to clarify genetic diversity and its meaning for species diversity in this family