Mitogenome and phylogenetic analyses support rapid diversification among species groups of small-eared shrews genus <i>Cryptotis</i> (Mammalia: Eulipotyphla: Soricidae)

The small-eared shrew genus Cryptotis is the third largest in the family Soricidae and occurs in North, Central, and northern South America. In Mexico and Central and South America, most species inhabit geographically isolated moist, montane habitats at middle and high elevations in a typical sky-island pattern. The 49 recognized species have been partitioned into as many as six species groups based on morphological and molecular phylogenetic studies. The relationships among these species groups are poorly resolved, and their evolutionary histories, including migration patterns and locomotor adaptations, remain unclear. Herein, we provide a new phylogeny incorporating complete mitochondrial genomes (mitogenomes) and supermatrix approach. We compared different evolutionary scenarios using approximately unbiased (AU), Kishino-Hasegawa (KH), and Shimodaira-Hasegawa (SH) statistical tests. The phylogenetic hypothesis based on mitogenomes revealed novel relationships supporting a basal position for the Cryptotis parvus-group in the genus, and a close relationship between C. gracilis and one clade of the C. thomasi-group. The former relationship is consistent with the least derived humerus morphology and northern distribution of the species. The latter relationship implies multiple migrations between Central and South America. The lack of fine resolution for the species group relationships may be due partly to the lack of taxon sampling. In contrast, multi-approach analyses suggest that the unresolved relationships may be a result of rapid diversification during the early stages of Cryptotis evolution.小耳鼩鼱属物种分布于北美洲、中美洲以及南美洲北部。墨西哥以及中、南美洲地区的大部分物种栖息于中、高海拔的湿润山地环境，不同的山地之间相互隔离，呈现典型的“天空之岛”分布格局。基于分子生物学和形态学证据，已知的49个物种被归于6个种组，但由于种组之间的进化关系一直未得到解决，关于该类群的迁徙历史和运动机能的适应性演化途径一直不清楚。该研究使用全线粒体基因组以及序列矩阵的方法重建了小耳鼩属的系统进化关系，并且通过AU、KH和SH检验对不同进化假说进行比较。 线粒体基因组支持北美小耳鼩（ Cryptotis parvus）种组是该属最原始的进化支系，这与北美小耳鼩原始的肱骨形态、以及最靠北的分布吻合； C. thomasi种组和 C. gracilis亲缘关系紧密，暗示小耳鼩属物种可能多次在中美洲和南美洲之间迁徙。六个种组之间的进化关系仍未得到完美解决，其原因可能是由于部分类群的缺失，以及小耳鼩属早期辐射演化造成的。.