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首页> 外文期刊>Herpetologica >Allozyme and mitochondrial DNA variation in the tailed frog (Anura : Ascaphus): The influence of geography and gene flow
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Allozyme and mitochondrial DNA variation in the tailed frog (Anura : Ascaphus): The influence of geography and gene flow

机译：尾蛙中的同工酶和线粒体DNA变异（Anura：Ascaphus）：地理和基因流的影响

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摘要

In this paper we support the division of the previously monotypic genus Ascaphus into two species based on an analysis of 23 allozyme loci from 34 populations. We use maximum likelihood to estimate the Ascaphus phylogeny from the allozyme data and find strongly supported monophyletic Rocky Mountain and Pacific clades. In a nonhierarchal, model-based cluster analysis of the data, each of the 1085 individual genotypes is correctly assigned to either Ascaphus montanus or A. truei with a high probability. We also find a virtually fixed difference between the species at the Pgm-2 locus. Within A. truei, we find a lack of significant pairwise F-ST values among populations from the Coast and central Cascades Mountains, suggesting relatively recent range expansion or contemporary gene flow among these populations. Olympic Mountains populations form a discrete clade in the allozyme topology and are fixed for a unique allele at the Lap locus. These populations remain isolated from the remainder of the species' range based on pairwise FST values. The four southernmost A. truei populations each show significant allelic divergence from the remaining populations (based on pairwise F-ST values), suggesting climate-induced isolation. In addition, we extend mtDNA sampling within the Rocky Mountains and sequence 530 nucleotides from the mtDNA Cytochrome b (cyt b) gene in 12 previously unsampled A. montanus populations. This additional sampling defines the geographic extent of a southern mtDNA clade distinguished on average by 0.024 substitutions per site from the northern clade. We use nested clade analysis, a coalescent-based divergence by isolation with migration model (MDIV), maximum-likelihood estimation of the mtDNA topology, and Bayesian model-based genotype assignment, to test predictions from two hypotheses: the western refugia hypothesis, which claims that A. montanus persisted in refugia west of the Snake River during Pleistocene glacial maxima, and the dual refugia hypothesis, which asserts that A. montanus occupied refugia within the Salmon and Clearwater River Valleys during glacial maxima. Our data do not support predictions of the western refugia hypothesis. Nested-clade analysis, estimated dates of lineage divergence supplied by MDIV, and the mtDNA topology support predictions of the dual refugia hypothesis; however, the allozyme topology fails to support some of these predictions. Allozyme and mtDNA data endorse the preliminary recognition of a minimum of two Evolutionarily Significant Units (ESUs) within A. truei: (1) populations from the Olympic Mountains and (2) populations south of the Umpqua River. Two ESUs are also suggested within A. montanus: (1) populations south of the South Fork of the Salmon River, and (2) populations to the north and west of the Salmon River (including the Blue, Wallowa and Seven Devils Mountains). The MDIV analysis indicates an exchange rate of 10 migrants per generation between the northern ESU and the southern ESU.
机译：在本文中，我们基于对34个种群的23个同工酶基因座的分析，支持将以前的单型属Ascaphus分为两个物种。我们使用最大可能性从同工酶数据估计阿斯卡普斯的系统发育，并发现强烈支持的单系落基山和太平洋进化枝。在基于数据的非分层，基于模型的聚类分析中，将1085个单独的基因型中的每一个都以很高的概率正确地分配给了Ascaphus montanus或A. truei。我们还在Pgm-2基因座上发现了物种之间的几乎固定的差异。在A. truei内，我们发现海岸和喀斯喀特山脉中部的种群之间缺乏显着的成对F-ST值，这表明这些种群中相对较近的范围扩展或当代基因流动。奥林匹克山种群在同工酶拓扑结构中形成离散的进化枝，并固定为膝上基因座的独特等位基因。根据成对的FST值，这些种群仍与该物种其余范围保持隔离。四个最南端的真叶志贺菌种群均显示与其余种群有显着等位基因差异（基于成对的F-ST值），表明气候诱导的隔离。此外，我们在落基山脉内扩展了mtDNA采样，并在12个先前未采样的褐藻种群中从mtDNA细胞色素b（cyt b）基因测序了530个核苷酸。这项额外的采样确定了南部mtDNA进化枝的地理范围，平均而言，每个位点与北部进化枝有0.024取代。我们使用巢式进化枝分析，通过与迁移模型（MDIV）隔离的基于聚结的发散，mtDNA拓扑结构的最大似然估计以及基于贝叶斯模型的基因型分配，来测试来自以下两个假设的预测：西方避难所假设声称在更新世冰期最大值期间，芒草属植物在Snake河以西的避难所和双重避难所假说一直存在，该假说断言山茱mon在冰河最大值期间在鲑鱼和清水河谷内占据了避难所。我们的数据不支持对西方避难所假说的预测。巢式分析，MDIV提供的谱系分歧估计日期以及mtDNA拓扑结构支持对双重避难所假说的预测;但是，同工酶拓扑无法支持其中的某些预测。等位酶和线粒体DNA数据支持初步识别真假单胞菌中至少两个进化重要单位（ESU）：( 1）来自奥林匹克山的种群和（2）Umpqua河以南的种群。在沼虾中还建议使用两种ESU：（1）鲑鱼河南叉以南的种群，以及（2）鲑鱼河以北和西部的种群（包括蓝，瓦洛阿和七魔鬼山）。 MDIV分析表明，北部ESU和南部ESU之间每代的移民率为10。

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