Portik Daniel M, Papenfuss Theodore J
Museum of Vertebrate Zoology and Department of Integrative Biology, 3101 Valley Life Sciences Building, University of California, Berkeley, CA, 94720-3160, USA.
BMC Evol Biol. 2015 Aug 6;15:152. doi: 10.1186/s12862-015-0417-y.
The Arabian Peninsula is home to a unique fauna that has assembled and evolved throughout the course of major geophysical events, including the separation of the Arabian Plate from Africa and subsequent collision with Eurasia. Opportunities for faunal exchanges with particular continents occurred in temporally distinct periods, and the presence of African, Western Eurasian, and South Asian derived taxa on the Arabian Peninsula signifies the complexity of these historical biogeographic events. The six true toad species (family Bufonidae) endemic to Arabian Peninsula present a considerable taxonomic and biogeographic challenge because they are part of a global bufonid radiation, including several genera surrounding the Arabian Peninsula, and difficult to discriminate morphologically. As they could be derived from African, Western Eurasian, or South Asian toad groups, elucidating their evolutionary relationships has important implications for historical biogeography. Here, we analyze a global molecular data set of 243 bufonid lineages, with an emphasis on new sampling from the Horn of Africa, Western Eurasia, South Asia, and the Arabian Peninsula, to reconstruct the evolutionary relationships of the Arabian species. We produce a robust time-calibrated phylogeny to infer the biogeographic history of this group on and around the Arabian Peninsula.
Our phylogenetic analyses indicate two of the endemic Arabian toad species, "Bufo" tihamicus and "Bufo" arabicus, evolved independently within the African genus Amietophrynus. We confirm the Arabian species Duttaphrynus dhufarensis is of South Asian origin, but do not find evidence for the Asian genus Duttaphrynus being present in the Horn of Africa, discrediting a previously proposed Asian bufonid dispersal event to Africa. We also do not find evidence of the African genus Amietophrynus occurring in South Asia, suggesting that unlike many other vertebrate taxa, toads have not used the Arabian Peninsula as a stepping-stone for trans-continental dispersal. Our divergence dating estimates strongly suggest the formation of the Red Sea drove simultaneous divergences between two of the Arabian species (A. tihamicus comb. nov. and A. arabicus comb. nov.) and their xclosest mainland African relatives in the Early Miocene. We estimate the divergence of D. dhufarensis with its closest South Asian relatives occurred in the mid to Late Miocene, suggesting the temporary or permanent land connections between the Arabian plate and Eurasia facilitated dispersal of this lineage to the Arabian Peninsula.
The Arabian bufonid assemblage, despite being comparatively depauperate with respect to surrounding continents, exemplifies the faunal pattern of the Arabian Peninsula, namely being a complex admixture of African, Western Eurasian, and South Asian elements. The historical biogeographic patterns exhibited by Arabian toads and their allies are concordant with studies of other vertebrate taxa, building support for the role of major geological events in driving simultaneous vicariance and dispersal events around the Arabian Peninsula. Although many taxa or groups exhibiting disjunct Afro-Arabian distributions appear to have dispersed more recently from the Horn of Africa via a southern land bridge or overwater dispersal, both Amietophrynus tihamicus and A. arabicus likely represent true African relicts resulting from vicariance associated with the Red Sea formation, a pattern that so far is rare among the vertebrate species investigated.
阿拉伯半岛拥有独特的动物群，这些动物群在包括阿拉伯板块与非洲分离以及随后与欧亚大陆碰撞等重大地球物理事件过程中聚集并演化。与特定大陆进行动物交流的机会出现在不同的时期，阿拉伯半岛上源自非洲、西欧亚和南亚的类群表明了这些历史生物地理事件的复杂性。阿拉伯半岛特有的六种真蟾蜍物种（蟾蜍科）带来了相当大的分类学和生物地理学挑战，因为它们是全球蟾蜍辐射的一部分，包括阿拉伯半岛周边的几个属，并且在形态上难以区分。由于它们可能源自非洲、西欧亚或南亚蟾蜍类群，阐明它们的进化关系对历史生物地理学具有重要意义。在此，我们分析了一个包含243个蟾蜍科谱系的全球分子数据集，重点是来自非洲之角、西欧亚、南亚和阿拉伯半岛的新样本，以重建阿拉伯物种的进化关系。我们构建了一个可靠的时间校准系统发育树，以推断该类群在阿拉伯半岛及其周边地区的生物地理历史。
我们的系统发育分析表明，两种阿拉伯特有蟾蜍物种，即“蟾蜍”提哈米蟾蜍和“蟾蜍”阿拉伯蟾蜍，在非洲的阿氏蟾蜍属内独立进化。我们确认阿拉伯物种杜氏蟾蜍起源于南亚，但未找到亚洲杜氏蟾蜍属存在于非洲之角的证据，这否定了先前提出的亚洲蟾蜍科向非洲扩散的事件。我们也未找到非洲阿氏蟾蜍属出现在南亚的证据，这表明与许多其他脊椎动物类群不同，蟾蜍没有将阿拉伯半岛作为跨大陆扩散的跳板。我们的分歧时间估计强烈表明，红海的形成导致了两种阿拉伯物种（新组合的提哈米阿氏蟾蜍和阿拉伯阿氏蟾蜍）与其在非洲大陆最亲近的亲属在中新世早期同时发生分歧。我们估计杜氏蟾蜍与其在南亚最亲近的亲属的分歧发生在中新世中期至晚期，这表明阿拉伯板块与欧亚大陆之间的临时或永久陆地连接促进了该谱系向阿拉伯半岛扩散。
阿拉伯蟾蜍科组合尽管相对于周边大陆来说种类较少，但体现了阿拉伯半岛的动物群模式，即非洲、西欧亚和南亚元素的复杂混合。阿拉伯蟾蜍及其近缘物种所展现的历史生物地理模式与其他脊椎动物类群的研究结果一致，为重大地质事件在推动阿拉伯半岛周围同时发生的隔离分化和扩散事件中所起的作用提供了支持。尽管许多呈现间断的非洲 - 阿拉伯分布的类群或群体似乎是最近通过南部陆桥或水上扩散从非洲之角扩散而来，但提哈米阿氏蟾蜍和阿拉伯阿氏蟾蜍很可能代表了真正的非洲残遗物种，是与红海形成相关的隔离分化的结果，这种模式在迄今为止所研究的脊椎动物物种中较为罕见。
