The southeastern Nearctic is a biodiversity hotspot that is also rich in cryptic species. Numerous hypotheses (e.g., vicariance, local adaptation, and Pleistocene speciation in glacial refugia) have been tested in an attempt to explain diversification and the observed pattern of extant biodiversity. However, previous phylogeographic studies have both supported and refuted these hypotheses. Therefore, while data support one or more of these diversification hypotheses, it is likely that taxa are forming within this region in species-specific ways. Here, we generate a genomic data set for the cornsnakes (Pantherophis guttatus complex), which are widespread across this region, spanning both biogeographic barriers and climatic gradients. We use phylogeographic model selection combined with hindcast ecological niche models to determine regions of habitat stability through time. This combined approach suggests that numerous drivers of population differentiation explain the current diversity of this group of snakes. The Mississippi River caused initial speciation in this species complex, with more recent divergence events linked to adaptations to ecological heterogeneity and allopatric Pleistocene refugia. Lastly, we discuss the taxonomy of this group and suggest there may be additional cryptic species in need of formal recognition.

中文翻译：

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东南部近北生物的生物地理障碍，更新世避难所和气候梯度推动了玉米蛇（Pantherophis guttatus复合体）的多样化。

东南部的Nearctic是一个生物多样性热点，也富含神秘物种。为了解释多样性和观察到的现存生物多样性模式，对许多假说（例如，冰川变迁中的戒备，局部适应和更新世物种形成）进行了测试。但是，以前的系统地理学研究都支持并驳斥了这些假设。因此，尽管数据支持了这些多样化假设中的一个或多个，但很可能在该区域内以物种特定的方式形成了分类群。在这里，我们为玉米蛇（Pantherophis guttatus复合体）生成了一个基因组数据集，该数据集遍及该地区，涵盖了生物地理学障碍和气候梯度。我们使用系统地理学模型选择与后生生态位生态模型相结合来确定随时间变化的栖息地稳定性区域。这种综合的方法表明，众多的人口分化驱动因素解释了这组蛇的当前多样性。密西西比河在该物种复合体中引起了最初的物种形成，更多的近期发散事件与对生态异质性和异相更新世避难所的适应有关。最后，我们讨论该组的分类法，并建议可能需要正式承认的其他隐性物种。与最近的发散事件有关，这些事件与适应生态异质性和异相更新世避难所有关。最后，我们讨论该组的分类法，并建议可能需要正式承认的其他隐性物种。与最近的发散事件有关，这些事件与适应生态异质性和异相更新世避难所有关。最后，我们讨论该组的分类法，并建议可能需要正式承认的其他隐性物种。