Gene pool sharing and genetic bottleneck effects in subpopulations of Eschweilera ovata (Cambess.) Mart. ex Miers (Lecythidaceae) in the Atlantic Forest of southern Bahia, Brazil

Abstract Forest loss and fragmentation are the main threats to the maintenance of the Atlantic Forest, an important global biodiversity hotspot. Because of the current critical level of deforestation, ecological corridors are needed to facilitate species dispersion and gene flow among fragments. This study was conducted to investigate the genetic variability and gene pool sharing of Eschweilera ovata in five forest remnants in southern Bahia, Brazil using nuclear simple sequence repeat (nSSR) and plastid simple sequence repeat (cpSSR) microsatellite markers. cpSSR marker analysis revealed the domains of four haplotypes, showing that 80% of the individuals had only four maternal origins, reflecting a founder effect and/or genetic bottleneck. The results of cpSSR and nSSR analyses indicated moderate genetic diversity, particularly in conservation units with full protection, which showed the best parameters of all areas evaluated. Another indication of the susceptibility of these populations to forest loss and fragmentation was the strong genetic bottleneck observed. In contrast, genetic structure analyses (FST and discriminant analysis of principal components) revealed gene pool sharing between the subpopulations, which may reflect the historical gene flow that occurred before forest fragmentation.

摘要 森林丧失与片段化是维持大西洋森林（Atlantic Forest）的核心威胁，该生态系统作为全球重要的生物多样性热点（biodiversity hotspot），其健康存续正面临严峻挑战。鉴于当前森林砍伐已达临界水平，亟需构建生态廊道以促进各森林片段间的物种扩散与基因交流。本研究以巴西巴伊亚州南部5处森林残存斑块为研究对象，利用核简单序列重复（nSSR）与质体简单序列重复（cpSSR）两类微卫星标记，对卵叶埃斯威勒拉木（Eschweilera ovata）的遗传变异与基因库共享情况展开探究。cpSSR标记分析共检测到4种单倍型，结果显示80%的个体仅隶属于4种母系起源，这反映出奠基者效应与遗传瓶颈现象。cpSSR与nSSR的分析结果均表明种群整体呈现中等水平的遗传多样性，其中受全面保护的保护单元在所有评估区域中展现出最优的遗传多样性参数。本次研究观测到的强烈遗传瓶颈，进一步印证了此类种群对森林丧失与片段化的敏感性。与之相反，遗传结构分析（涵盖遗传分化系数FST与主成分判别分析（discriminant analysis of principal components））结果显示，各亚种群间存在基因库共享现象，这或可反映森林片段化发生前曾存在的历史基因交流。