Data from: Delimiting species in the genus Otospermophilus (Rodentia: Sciuridae) using genetics, ecology, and morphology

We apply an integrative taxonomy approach to delimit species of ground squirrels in the genus Otospermophilus because the diverse evolutionary histories of organisms shape the existence of taxonomic characters. Previous studies of mitochondrial DNA from this group recovered three divergent lineages within Otospermophilus beecheyi separated into northern, central, and southern geographical populations, with Otospermophilus atricapillus nested within the southern lineage of O. beecheyi. To further evaluate species boundaries within this complex, we collected additional genetic data (one mitochondrial locus, 11 microsatellite markers, and 11 nuclear loci), environmental data (eight bioclimatic variables), and morphological data (23 skull measurements). We used the maximum number of possible taxa (O. atricapillus, Northern O. beecheyi, Central O. beecheyi, and Southern O. beecheyi) as our operational taxonomic units (OTUs) and examined patterns of divergence between these OTUs. Phenotypic measures (both environmental and morphological) showed little differentiation among OTUs. By contrast, all genetic datasets supported the evolutionary independence of Northern O. beecheyi, although they were less consistent in their support for other OTUs as distinct species. Based on these data, we support the conclusions from a previous study that synonymized O. atricapillus with O. beecheyi, and we elevate the northern lineage of O. beecheyi to a separate species.

本研究采用整合分类学方法（integrative taxonomy approach），对美洲黄鼠属（Otospermophilus）内地松鼠的物种界限进行界定，因生物多样的演化历程塑造了分类学特征的形成。此前针对该类群的线粒体DNA（mitochondrial DNA）研究，在加州黄鼠（Otospermophilus beecheyi）内部检出3个分化支系，分别对应北部、中部与南部地理种群，且黑头美洲黄鼠（Otospermophilus atricapillus）嵌套于加州黄鼠的南部支系之中。为进一步评估该类群内的物种边界，本研究采集了额外的遗传数据：1个线粒体基因座、11个微卫星标记（microsatellite markers）、11个核基因座（nuclear loci），以及环境数据（8个生物气候变量，bioclimatic variables）与形态学数据（23项头骨量度，skull measurements）。本研究以预设的全部可能分类群（黑头美洲黄鼠、北部加州黄鼠、中部加州黄鼠及南部加州黄鼠）作为操作分类单元（operational taxonomic units，OTU），并检验了这些操作分类单元间的分化模式。表型测量数据（涵盖环境与形态两类）显示，各操作分类单元间几乎无分化。与之形成对照的是，所有遗传数据集均支持北部加州黄鼠的演化独立性，尽管它们在支持其余操作分类单元为独立物种方面的一致性较弱。基于上述数据，本研究支持此前一项将黑头美洲黄鼠归并为加州黄鼠同物异名的研究结论，并将加州黄鼠的北部支系提升为独立物种。