Molecular systematics and biodiversity of the Cryptotis mexicanus group (Eulipotyphla: Soricidae): two new species from Honduras supported

Small-eared shrews of the genus Cryptotis (Mammalia: Eulipotyphla: Soricidae) are widespread in the northern Neotropics. Systematic studies of these shrews over the past two decades have revealed previously undocumented morphological and species diversity, resulting in a quadrupling of the number of recognized species. Unfortunately, a small proportion of the species in the genus have been included in molecular phylogenetic studies, and evolutionary relationships within the genus are incompletely known. Traditionally, species have been assigned to four or five morphologically defined ‘species groups’, but tests of the monophyly of some of these groups show weak support and relationships amongst species groups remain somewhat speculative. The largest species group is the C. mexicanus group inhabiting Mexico and northern Central America. We studied sequences from mitochondrial cytochrome-b and 16S genes, as well as nuclear ApoB and BRCA1 genes from 22 species of Cryptotis, including 15 species in the C. mexicanus group. Our combined analysis shows that the C. goldmani subgroup is very weakly supported as monophyletic; however, the C. mexicanus group as a whole is not monophyletic. Our molecular phylogenetic analyses confirm the distinctiveness of two newly described species (C. celaque and C. mccarthyi) from isolated highlands of western Honduras and illustrate their relationship with other species formerly considered part of a widespread C. goodwini.

隶属于哺乳纲（Mammalia）、真盲缺目（Eulipotyphla）、鼩鼱科（Soricidae）的小耳鼩鼱属（Cryptotis）物种，广泛分布于新热带区（Neotropics）北部。过去二十年间，针对这类鼩鼱的系统分类研究（systematic studies）揭示了此前未被记录的形态多样性与物种多样性，使得已正式确认的物种种数增至原来的四倍。遗憾的是，该属仅有极小比例的物种被纳入分子系统发育研究（molecular phylogenetic studies），属内的演化亲缘关系仍未完全明晰。传统上，该属物种被划分为4至5个基于形态学特征定义的‘物种类群’，但对其中部分类群单系性（monophyly）的检验仅获得微弱支持，各类群间的亲缘关系仍颇具推测性。其中物种数量最多的类群为栖息于墨西哥及中美洲北部的墨西哥类群（C. mexicanus group）。本研究分析了22种小耳鼩鼱属（Cryptotis）物种的线粒体细胞色素b基因（mitochondrial cytochrome-b）、16S基因（16S genes）序列，以及核基因ApoB与BRCA1序列，其中包含15个隶属于墨西哥类群（C. mexicanus group）的物种。联合系统发育分析结果显示，戈德曼亚类群（C. goldmani subgroup）的单系性仅获得极微弱的支持；而墨西哥类群（C. mexicanus group）整体并非单系群。本分子系统发育分析证实了2个新近描述的物种——发现于洪都拉斯西部孤立高地的C. celaque与C. mccarthyi——的物种独立性，并阐明了它们与此前被广泛认为隶属于广布种C. goodwini的其他物种之间的亲缘关系。