Church Sheri A, Kraus Johanna M, Mitchell Joseph C, Church Don R, Taylor Douglas R
University of Virginia, Department of Biology, Charlottesville, Virginia 22903, USA.
Evolution. 2003 Feb;57(2):372-83. doi: 10.1554/0014-3820(2003)057[0372:EFMPRI]2.0.CO;2.
Pleistocene glaciations were important determinants of historical migration and, hence, current levels of genetic diversity within and among populations. In many cases, these historical migrations led to the existence of disjunct populations of plants and animals. However, the origin and timing of arrival of these disjunct populations is often debated. In the current study, we identify potential refugia and estimate the timing of vicariance events of the eastern tiger salamander, Ambystoma tigrinum tigrinum, using mitochondrial sequence data. The results suggest a vicariant event 0.75-2 million years ago, separating the tiger salamanders to the east and west of the Apalachicola River Basin. East of the Appalachians, there appear to be multiple independent refugia with little migration among the remaining populations. In particular, populations along the Atlantic Coastal Plain were likely isolated in a coastal plain refugium in the Carolinas. Migrants from this refugium were the likely source of colonists for populations occupying previously glaciated areas along the northeastern Atlantic Coast. A second potential refugium occurs in the Blue Ridge Mountains of western Virginia. This refugium contains a disjunct population of the eastern tiger salamander, as well as a community of nearly 70 other disjunct plant and animal species. The tiger salamanders here have been isolated from other populations for 200,000-500,000 years. These results suggest that disjunct mountain populations of Coastal Plain species may have existed in situ throughout the Pleistocene in Appalachian refugia. Therefore, these disjunct populations are not of recent origin, but rather exist as relicts of a warmer, more widespread fauna and flora that is now restricted to the Coastal Plain.
更新世冰川作用是历史迁徙的重要决定因素，因此也是种群内部和种群之间当前遗传多样性水平的重要决定因素。在许多情况下，这些历史迁徙导致了动植物不连续种群的存在。然而，这些不连续种群的起源和到达时间常常存在争议。在当前的研究中，我们利用线粒体序列数据确定了东部虎螈（Ambystoma tigrinum tigrinum）的潜在避难所，并估计了其地理隔离事件的时间。结果表明，在0.75 - 200万年前发生了一次地理隔离事件，将阿巴拉契科拉河流域以东和以西的虎螈分隔开来。在阿巴拉契亚山脉以东，似乎存在多个独立的避难所，其余种群之间几乎没有迁移。特别是，大西洋沿岸平原的种群可能在卡罗来纳州的一个沿海平原避难所中隔离。来自这个避难所的迁徙者可能是占据东北大西洋沿岸先前冰川覆盖地区种群的殖民者来源。第二个潜在的避难所位于弗吉尼亚州西部的蓝岭山脉。这个避难所包含东部虎螈的一个不连续种群，以及近70种其他不连续动植物物种的群落。这里的虎螈已经与其他种群隔离了20万 - 50万年。这些结果表明，沿海平原物种的不连续山地种群可能在整个更新世都存在于阿巴拉契亚避难所中。因此，这些不连续种群并非近期起源，而是作为现在局限于沿海平原的更温暖、分布更广泛的动植物群的遗迹而存在。
