Departamento de Zoologia, Universidade Estadual Paulista Julio de Mesquita Filho, Avenida 24A 1515, Rio Claro, SP 13506-900, Brazil.
Mol Phylogenet Evol. 2010 Jun;55(3):1018-31. doi: 10.1016/j.ympev.2010.02.003. Epub 2010 Feb 6.
The Plio-Pleistocene refugia hypothesis recently gained support in explaining Brazilian Atlantic Forest megadiversity from combined analyses of species paleodistributions and genetic diversity. Here we examine genetic differentiation and historical distributions in the Rhinella crucifer group of toads, endemic to and widely distributed within this biome. We analyzed sequences of mitochondrial (control region, ND1, and ND2) and nuclear (beta-crystallin and rhodopsin) DNA markers from 65 individuals representing five species. We found deep structure across the range at mitochondrial markers; genetic diversity is geographically structured in four main haplotype clades with the oldest divergence, dated to the Pliocene, between the southernmost populations and other regions of the species' range. Remaining populations are distributed in haplotype clades that may have diverged throughout the Pleistocene. Our paleoecological distribution models support a scenario of habitat fragmentation associated with glacial cycling, but we found limited congruence of phylogeographic patterns with the refugia. We found that some genetic breaks geographically coincide with putative barriers associated to neotectonic activity, but finer-scale sampling will be necessary to test the relative importance of distinct isolation mechanisms. Overall, the data refute the recently proposed hypothesis of a southern Holocene colonization of the Atlantic Forest from northern refugia, suggesting instead persistence of forested habitats in the south. Our unexpected results underscore the need to consider distinct organismal histories in planning biome-level conservation. We discuss species correspondence to clades recovered in our phylogenetic analyses.
最近，从物种古分布和遗传多样性的综合分析中，中新世-更新世避难所假说得到了支持，用来解释巴西大西洋森林的大物种多样性。在这里，我们研究了广泛分布于该生物群内的蟾蜍 Rhinella crucifer 组的遗传分化和历史分布。我们分析了来自 65 个个体的线粒体（控制区、ND1 和 ND2）和核（β-晶体蛋白和视蛋白）DNA 标记的序列。我们在整个范围内的线粒体标记物中发现了深度结构；遗传多样性在四个主要单倍型分支中具有地理结构，最古老的分歧发生在更新世，最南端的种群与该物种分布范围的其他地区之间。其余的种群分布在可能在整个更新世分化的单倍型分支中。我们的古生态分布模型支持与冰川循环相关的生境破碎化情景，但我们发现，与避难所相比，系统发育格局的一致性有限。我们发现，一些遗传断裂在地理上与与新构造活动相关的假定障碍相吻合，但需要更精细的采样来测试不同隔离机制的相对重要性。总的来说，数据反驳了最近提出的从北方避难所到大西洋森林的南部全新世殖民的假说，反而表明南部森林生境的持续存在。我们意想不到的结果强调了在规划生物群落水平保护时需要考虑不同的生物历史。我们讨论了与我们的系统发育分析中恢复的进化枝相对应的物种。
