School of Biological Sciences, Environment Centre Wales, Bangor University, Bangor LL57 2UW, UK.
Mol Ecol. 2013 Feb;22(4):1134-57. doi: 10.1111/mec.12157. Epub 2013 Jan 3.
Evidence from numerous Pan-African savannah mammals indicates that open-habitat refugia existed in Africa during the Pleistocene, isolated by expanding tropical forests during warm and humid interglacial periods. However, comparative data from other taxonomic groups are currently lacking. We present a phylogeographic investigation of the African puff adder (Bitis arietans), a snake that occurs in open-habitat formations throughout sub-Saharan Africa. Multiple parapatric mitochondrial clades occur across the current distribution of B. arietans, including a widespread southern African clade that is subdivided into four separate clades. We investigated the historical processes responsible for generating these phylogeographic patterns in southern Africa using species distribution modelling and genetic approaches. Our results show that interior regions of South Africa became largely inhospitable for B. arietans during glacial maxima, whereas coastal and more northerly areas remained habitable. This corresponds well with the locations of refugia inferred from mitochondrial data using a continuous phylogeographic diffusion model. Analysis of data from five anonymous nuclear loci revealed broadly similar patterns to mtDNA. Secondary admixture was detected between previously isolated refugial populations. In some cases, this is limited to individuals occurring near mitochondrial clade contact zones, but in other cases, more extensive admixture is evident. Overall, our study reveals a complex history of refugial isolation and secondary expansion for puff adders and a mosaic of isolated refugia in southern Africa. We also identify key differences between the processes that drove isolation in B. arietans and those hypothesized for sympatric savannah mammals.
来自众多泛非稀树草原哺乳动物的证据表明，在更新世期间，非洲存在开阔栖息地避难所，这些避难所被温暖湿润的间冰期扩张的热带森林隔开。然而，目前其他分类群的比较数据仍然缺乏。我们对非洲膨蝰（Bitis arietans）进行了系统地理学研究，这是一种在撒哈拉以南非洲的开阔栖息地形成中出现的蛇类。在 B. arietans 的当前分布范围内，存在多个并置的线粒体支系，包括一个广泛分布的南部非洲支系，该支系进一步分为四个独立的支系。我们使用物种分布模型和遗传方法研究了导致这些南部非洲系统地理学模式的历史过程。我们的结果表明，在冰川高峰期，南非内陆地区对 B. arietans 变得极不适宜居住，而沿海和更北部地区仍然适宜居住。这与使用连续系统地理学扩散模型从线粒体数据推断出的避难所位置非常吻合。对来自五个匿名核基因座的数据进行分析显示出与 mtDNA 大致相似的模式。以前隔离的避难种群之间发生了次级混合。在某些情况下，这种情况仅限于存在于线粒体支系接触区附近的个体，但在其他情况下，明显存在更广泛的混合。总体而言，我们的研究揭示了膨蝰隔离和次级扩张的复杂历史，以及南部非洲隔离避难所的镶嵌模式。我们还确定了驱动 B. arietans 隔离的过程与假设的共生稀树草原哺乳动物的过程之间的关键差异。
