Abstract

Dynamic climatic oscillations during the Pleistocene had profound effects on the distribution of species across North America. Although the role of historical climate change on speciation remains controversial, the impact on genetic variation within species has been well documented. Analyses of mtDNA sequences from the cytochrome oxidase I gene (911 bp) for 115 individuals of Odontotaenius disjunctus was combined with ecological niche modelling (ENM) to infer the demographic and population differentiation scenarios under present and past conditions. We inferred three lineages that diverged during the Pleistocene and replace each other geographically across the eastern United States. One of these lineages traverses previously identified genetic barriers for terrestrial animals including the Mississippi and Apalachicola Rivers and the Appalachian Mountains. We observed overlapping ranges between two haplotype groups as well as a region of secondary contact associated with ecological transition zone in northern Florida. The two continental lineages depict a genetic signature of a recent population increase associated with expanding niche envelope, whereas the clade restricted to peninsular Florida shows stable populations in a shrinking niche envelope. Given the lack of ecological separation, overlapping distribution of haplogroups and the presence of secondary contact zones, the taxonomic status of these lineages must await robust testing using multilocus DNA data to assess species boundaries.

摘要

更新世期间的动态气候波动对北美物种的分布产生了深远的影响。尽管历史气候变化对物种形成的作用仍存在争议，但对物种内遗传变异的影响已得到充分证明。115名分离齿鳖个体细胞色素氧化酶 I基因 (911 bp)的 mtDNA 序列分析与生态位模型（ENM）相结合，以推断当前和过去条件下的人口和人口分化情景。我们推断出三个在更新世发生分歧并在美国东部地理上相互替代的血统。其中一个谱系跨越了先前确定的陆地动物的遗传障碍，包括密西西比河和阿巴拉契科拉河以及阿巴拉契亚山脉。我们观察到两个单倍型组之间的重叠范围以及与佛罗里达州北部生态过渡区相关的二次接触区域。这两个大陆谱系描绘了与扩大生态位信封相关的最近人口增加的遗传特征，而仅限于佛罗里达半岛的进化枝在不断缩小的生态位信封中显示出稳定的种群。鉴于缺乏生态分离、单倍群的重叠分布和次要接触区的存在，这些谱系的分类地位必须等待使用多位点 DNA 数据来评估物种边界的稳健测试。