Integrative Taxonomy Reveals a New Species of the Eisenia andrei/fetida Complex (Clitellata: Lumbricidae) From the Guizhou Plateau, China

The Eisenia andrei /fetida complex represents one of the most widely distributed and taxonomically challenging groups of earthworms, exhibiting high cryptic diversity and complex species boundaries. Here, we describe a new species, Eisenia zhongshanensis sp. nov., from Wangjiazhai Town, Zhongshan District, Liupanshui City, located on the Guizhou Plateau, China. Species delimitation was performed using an integrative taxonomic approach combining morphological examination and molecular phylogenetic analyses based on two molecular markers: the mitochondrial cytochrome c oxidase subunit I ( COI ) gene and the nuclear 28S ribosomal RNA ( 28S rRNA) gene. Phylogenetic analyses revealed that the new species belongs to the Eisenia fetida complex but forms a highly supported independent lineage (posterior probability ≥ 0.95; bootstrap value ≥ 70%). The new species is distinguished from all known congeners by its rhombus‐shaped spermathecae, three pairs of spermathecal pores in 6/7/8/9, and unique tanylobous prostomium. The genetic distances (K2P) between the new species and its closest relatives ranged from 12.3% to 15.0% for COI, and 1.7% to 2.1% for 28S rRNA. This discovery highlights the underestimated biodiversity of the Eisenia complex in high‐altitude regions of southwestern China and underscores the necessity of applying integrative taxonomic approaches to resolve cryptic diversity in lumbricid earthworms.