Origin of a cryptic lineage in a threatened reptile through isolation and historical hybridization
Origin of a cryptic lineage in a threatened reptile through isolation and historical hybridization
复制标题
通过隔离和历史杂交发现受威胁爬行动物的神秘谱系的起源
作者：
MG Sovic;AC Fries;HL Gibbs
识别系统发育上不同的谱系并了解它们产生的进化过程是系统发育地理学的重要目标。这些信息还可以帮助定义濒危物种的保护单位。基因组规模数据集的可用性和新颖的分析方法正在改变这种分析，这些方法用于统计比较不同历史情景作为系统发育地理学模式的原因。在这里，我们使用基因组规模的限制性位点相关 DNA 测序 (RADseq) 数据来测试濒临灭绝的东部侏儒响尾蛇 (Sistrurus catenatus) 的不同谱系。然后，我们使用基于聚结的建模技术来确定导致该物种谱系起源的进化机制。我们在密西西比河以东的链环蛇中发现了关于不同系统发育谱系的模棱两可的证据，但有力地支持了该蛇分布范围西缘的一个先前未被识别的谱系，该谱系以美国爱荷华州的种群为代表。这些种群的蛇表现出与附近未受威胁的姐妹物种（Sistrurus tergeminus）的基因混合模式。对历史人口统计模型的测试支持了这样的假设：爱荷华蛇的遗传独特性是由于 S. catenatus 和 S. tergeminus 之间的隔离和历史渗入相结合造成的。我们的工作提供了一个例子，说明基于模型的基因组规模数据分析如何帮助识别稀有物种的保护单位。
Identifying phylogenetically distinct lineages and understanding the evolutionary processes by which they have arisen are important goals of phylogeography. This information can also help define conservation units in endangered species. Such analyses are being transformed by the availability of genomic-scale data sets and novel analytical approaches for statistically comparing different historical scenarios as causes of phylogeographic patterns. Here, we use genomic-scale restriction-site-associated DNA sequencing (RADseq) data to test for distinct lineages in the endangered Eastern Massasauga Rattlesnake (Sistrurus catenatus). We then use coalescent-based modeling techniques to identify the evolutionary mechanisms responsible for the origin of the lineages in this species. We find equivocal evidence for distinct phylogenetic lineages within S. catenatus east of the Mississippi River, but strong support for a previously unrecognized lineage on the western edge of the range of this snake, represented by populations from Iowa, USA. Snakes from these populations show patterns of genetic admixture with a nearby non-threatened sister species (Sistrurus tergeminus). Tests of historical demographic models support the hypothesis that the genetic distinctiveness of Iowa snakes is due to a combination of isolation and historical introgression between S. catenatus and S. tergeminus. Our work provides an example of how model-based analysis of genomic-scale data can help identify conservation units in rare species.