Genetics, morphology and ecology reveal a cryptic pika lineage in the Sikkim Himalaya

Asian pika species are morphologically ∼similar and have overlapping ranges. This leads to uncertainty and species misidentification in the field. Phylogenetic analyses of such misidentified samples leads to taxonomic ambiguity. The ecology of many pika species remains understudied, particularly in the Himalaya, where sympatric species could be separated by elevation and/or substrate. We sampled, measured, and acquired genetic data from pikas in the Sikkim Himalaya. Our analyses revealed a cryptic lineage, Ochotona sikimaria, previously reported as a subspecies of O. thibetana. The results support the elevation of this lineage to the species level, as it is genetically divergent from O. thibetana, as well as sister species, O. cansus (endemic to central China) and O. curzoniae (endemic to the Tibetan plateau). The Sikkim lineage diverged from its sister species’ about 1.7–0.8 myr ago, coincident with uplift events in the Himalaya. Our results add to the recent spate of cryptic diversity identified from the eastern Himalaya and highlight the need for further study within the Ochotonidae.

亚洲鼠兔物种在形态上高度相似，且分布范围相互重叠，这导致野外鉴定时存在不确定性，极易出现物种误判。基于此类误鉴样本开展的系统发育分析，往往会引发分类学上的歧义。多数鼠兔物种的生态学特征仍未得到充分研究，尤其是在喜马拉雅地区——该区域的同域鼠兔物种可通过海拔或生境基质进行区分。本研究对喜马拉雅锡金段的鼠兔进行了采样、形态测量，并获取了其遗传数据。分析结果显示存在一个隐存支系：锡金鼠兔（Ochotona sikimaria），该类群此前被报道为藏南鼠兔（Ochotona thibetana）的亚种。研究结果支持将该支系提升为独立物种，因为它与藏南鼠兔、近缘姊妹物种中华鼠兔（Ochotona cansus，中国中部特有种）和高原鼠兔（Ochotona curzoniae，青藏高原特有种）均存在遗传分化。该锡金支系与其姊妹物种的分化时间约为170万至80万年前，这与喜马拉雅山脉的隆升事件时间相吻合。本研究结果进一步丰富了近期在东喜马拉雅地区发现的隐存多样性案例，并强调了针对鼠兔科（Ochotonidae）开展深入研究的必要性。