日前，萨维奇环北极分布假说首次得到检验，该工作是中科院动物所的专家做出的。据悉，起源于劳亚大陆的蛙类，目前间断地分布在欧洲中南部、朝鲜半岛及邻近地区、东南亚、北美南部。Savage JM在1973年提出了一个解释这种分布格局的假说，即萨维奇环北极分布假说：在第三纪早期，这些蛙类的分布比现在更靠北也更连续，形成一个环北极的分布格局，但发生于中新世的全球降温和北半球内陆干旱化两个事件使这些蛙类的分布区南移并且相互隔离开来。
萨维奇环北极分布假说影响广泛，但一直没有被检验过。中科院动物研究所动物进化与系统学院重点实验室李枢强研究组近期以劳亚大陆起源的铃蟾属蛙类为材料，首次对该生物地理假说进行了检验。该假说的一个重要推论是分布于不同隔离区域的支系间的分化时间不晚于上述气候事件发生的时间。作为唯一的分布于两个以上前述隔离区域的属级分类单元——铃蟾属，是验证该推论的理想材料。基于全面的样本和6000bp的线粒体和核基因分子标记，首先构建了铃蟾属的系统发育树。基于该树估计的铃蟾东南亚支系、东亚支系、欧洲支系全部三大支系间的分化时间均不显著晚于上述气候事件发生的时间。相关成果发表在最近出版的《分子进化与系统发育》（Molecular Phylogenetics and Evolution）杂志上。（生物谷Bioon.com）
生物谷推荐原始出处：
Molecular Phylogenetics and Evolution, Volume 52, Issue 1, July 2009, Pages 70-83
Toward understanding the distribution of Laurasian frogs: A test of Savage’s biogeographical hypothesis using the genus Bombina
Yuchi Zheng, Jinzhong Fu, Shuqiang Li
Several anuran groups of Laurasian origin are each co-distributed in four isolated regions of the Northern Hemisphere: central/southern Europe and adjacent areas, Korean Peninsula and adjacent areas, Indo-Malaya, and southern North America. Similar distribution patterns have been observed in diverse animal and plant groups. Savage [Savage, J.M., 1973. The geographic distribution of frogs: patterns and predictions. In: Vial, J.L. (Ed.), Evolutionary Biology of the Anurans. University of Missouri Press, Columbia, pp. 351–445] hypothesized that the Miocene global cooling and increasing aridities in interiors of Eurasia and North America caused a southward displacement and range contraction of Laurasian frogs (and other groups). We use the frog genus Bombina to test Savage’s biogeographical hypothesis. A phylogeny of Bombina is reconstructed based on three mitochondrial and two nuclear gene fragments. The genus is divided into three major clades: an Indo-Malaya clade includes B. fortinuptialis, B. lichuanensis, B. maxima, and B. microdeladigitora; a European clade includes B. bombina, B. pachypus, and B. variegata; and a Korean clade contains B. orientalis. The European and Korean clades form sister-group relationship. Molecular dating of the phylogenetic tree using the penalized likelihood and Bayesian analyses suggests that the divergence between the Indo-Malaya clade and other Bombina species occurred 5.9–28.6 million years ago. The split time between the European clade and the Korean clade is estimated at 5.1–20.9 million years ago. The divergence times of these clades are not significantly later than the timing of Miocene cooling and drying, and therefore can not reject Savage’s hypothesis. Some other aspects of biogeography of Bombina also are discussed. The Korean Peninsula and the Shandong Peninsula might have supplied distinct southern refugia for B. orientalis during the Pleistocene glacial maxima. In the Indo-Malaya clade, the uplift of the Tibetan Plateau might have promoted the split between B. maxima and the other species.
