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.

Cryptotis属（哺乳纲：真盲缺目：鼩鼱科）的小耳鼩广泛分布于新热带界北部区域。过去二十年间针对该类鼩鼱开展的分类学研究，揭示了此前未被记录的形态学与物种多样性，使得已确认物种数量增至原来的四倍。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，该属内的演化关系仍未完全明晰。传统上，该属物种被划分为4至5个基于形态学定义的“物种群”，但针对其中部分类群单系性的检验仅获得较弱的支持度，各物种群间的亲缘关系仍具有一定推测性。体型最大的物种群为栖息于墨西哥及中美洲北部的C. mexicanus种组。本研究针对22种Cryptotis属鼩鼱的线粒体细胞色素b（cytochrome-b）、16S基因，以及核基因ApoB与BRCA1的序列展开分析，其中包含15个隶属于C. mexicanus种组的物种。联合序列分析结果显示，C. goldmani亚组仅获得极弱的单系支持度；但整体而言，C. mexicanus种组并非单系类群。本次分子系统发育分析证实，来自洪都拉斯西部孤立高地的两个新描述物种（C. celaque与C. mccarthyi）具有独立的物种地位，并阐明了它们与此前被归为广布种C. goodwini的其他类群间的亲缘关系。