Data from: Insights into the origin and distribution of biodiversity in the Brazilian Atlantic forest hotspot: a statistical phylogeographic study using a low-dispersal organism

The relative importance of the processes that generate and maintain biodiversity is a major and controversial topic in evolutionary biology with large implications for conservation management. The Atlantic Forest of Brazil, one of the world's richest biodiversity hotspots, is severely damaged by human activities. To carry out an efficient conservation policy, a good understanding of spatial and temporal biodiversity patterns and their underlying evolutionary mechanisms is required. With this aim, we performed a comprehensive phylogeographic study using a low-dispersal organism, the land planarian species Cephaloflexa bergi (Platyhelminthes, Tricladida). Applying a multi-locus DNA sequence variation approach under the ABC framework we evaluated two scenarios proposed to explain the diversity of SAF region. We found that most sampled localities harbour high levels of genetic diversity, with lineages sharing old common ancestors that predate the Pleistocene. Remarkably, we detected the molecular hallmark of the isolation-by-distance effect and little evidence of a recent colonization of SAF localities; some populations nevertheless might result from very recent secondary contacts. We conclude that extant SAF biodiversity originated and has been shaped by complex interactions between ancient geological events and more recent evolutionary processes, while Pleistocene climate changes would have a minor influence in generating present day diversity. We also demonstrate that land planarians are an advantageous biological model for making phylogeographic and, particularly, fine-scale evolutionary inferences, and propose appropiate conservation policies.

驱动并维持生物多样性的各类过程的相对重要性，是进化生物学领域极具争议的核心议题，对生物多样性保护管理具有重大影响。作为全球物种最丰富的生物多样性热点（biodiversity hotspot）之一的巴西大西洋森林，正遭受人类活动的严重破坏。为制定高效的保护策略，亟需深入理解生物多样性的时空分布格局及其背后的进化机制。基于此研究目标，我们选取一种扩散能力较弱的生物——陆地扁形动物*Cephaloflexa bergi*（扁形动物门Platyhelminthes，三肠目Tricladida），开展了一项全面的系统地理学（phylogeography）研究。我们采用近似贝叶斯计算（Approximate Bayesian Computation, ABC）框架下的多位点DNA序列变异分析方法，对用以解释南美大西洋森林（South Atlantic Forest, SAF）区域生物多样性的两种演化情景进行了评估。研究发现，多数采样点位均拥有高水平的遗传多样性，其谱系共享的共同祖先可追溯至更新世（Pleistocene）之前的古老时期。值得注意的是，我们检测到了距离隔离效应（isolation-by-distance effect）的分子特征，且几乎未发现SAF区域近期定植的证据；不过部分种群可能源自极晚近的二次接触事件。我们据此得出结论：SAF区域现存的生物多样性起源于古老地质事件与近代进化过程之间的复杂相互作用，并受其塑造，而更新世气候变化对现今生物多样性的形成影响甚微。此外，我们证实陆地扁形动物是开展系统地理学研究，尤其是精细尺度进化推断的理想生物模型，并据此提出了适宜的保护策略。