Taxonomic notes on the Dorcus rubrofemoratus species group with the description of a new species (Coleoptera: Lucanidae: Lucaninae)

Abstract

A new species of stag beetle, Dorcus planus Guo, Xin, Zhan & Zhong, sp. nov., is described from Yunnan and Guangxi, China, based on integrative morphological and molecular evidence. The new species is a member of the D. rubrofemoratus group and is diagnosed by unique mandibular morphology, pronotal structure, and female elytral coloration. Although recovered as the sister species of D. haitschunus (Didier & Séguy, 1952) with strong nodal support, the two are separated by a COI distance of only 0.0243, a value well within the typical intraspecific range for Lucanidae. They nonetheless exhibit profound mandibular disparity, representing a remarkable case of rapid morphological evolution decoupled from mitochondrial differentiation. The taxonomic status of several related taxa is reassessed: D. magdaleinae (Lacroix, 1972) stat. rev., D. katctinensis Nagai, 2000 stat. rev., and D. lieni Maeda, 2012 stat. nov. are herein recognized as valid species. In addition, D. fukinukii (Schenk, 2000) is reported for the first time from Xizang, China as a national new record, and D. rubrofemoratus miyamai Nagai & Okazaki, 2005 is reported as a provincial new record from Shaanxi. The inconsistent application of subspecies criteria in lucanid taxonomy is also discussed.