Model-based analysis supports interglacial refugia over long-dispersal events in the diversification of two South American cactus species

Pilosocereus machrisii and P. aurisetus are cactus species within the P. aurisetus complex, a group of eight cacti that are restricted to rocky habitats within the Neotropical savannas of eastern South America. Previous studies have suggested that diversification within this complex was driven by distributional fragmentation, isolation leading to allopatric differentiation, and secondary contact among divergent lineages. These events have been associated with Quaternary climatic cycles, leading to the hypothesis that the xerophytic vegetation patches which presently harbor these populations operate as refugia during the current interglacial. However, owing to limitations of the standard phylogeographic approaches used in these studies, this hypothesis was not explicitly tested. Here we use Approximate Bayesian Computation to refine the previous inferences and test the role of different events in the diversification of two species within P. aurisetus group. We used molecular data from ch...Pilosocereus machrisii与P. aurisetus均隶属于P. aurisetus复合群（P. aurisetus complex），该复合群包含8种局限分布于南美洲东部新热带稀树草原岩石生境的仙人掌类群。此前研究表明，该复合群内的物种分化由分布片段化、隔离引发的异域分化（allopatric differentiation）以及分化谱系间的二次接触所驱动。上述事件与第四纪气候周期密切相关，由此提出假说：当前承载这些种群的旱生植被斑块在当前间冰期充当了避难所（refugia）。然而，由于此前研究采用的标准系统地理学（phylogeography）研究方法存在局限，该假说未得到明确检验。本研究采用近似贝叶斯计算（Approximate Bayesian Computation）修正既往推论，并检验P. aurisetus类群内两个物种的分化过程中各类事件的作用。本研究使用来自ch……的分子数据