Phylogenetic Insights and Species Delimitation of Eutyphoeus Earthworms in India Using Integrative taxonomy

Eutyphoeus Michaelsen 1900, a native genus of Indian earthworms, was recently reclassified into the Acanthodrilidae family (previously Octochaetidae). This genus has endemic species in various regions, including Myanmar, the Eastern Himalaya, the Indo-Gangetic lowlands, and the Northeast mountains. Phylogenetic research has revealed genuine connections between these taxa. To date, only three studies—two from Mizoram and one from Meghalaya—have utilized molecular systematics for these taxa. This study employed integrative taxonomy to explore the relationships among Eutyphoeus species in India. This made it easier to discriminate between closely related species using mitochondrial cytochrome oxidase I (CO1). A total of 48 CO1 sequences were analysed alongside sequences retrieved from databases using various species delimitation tools (ASAP and ABGD), phylogenetic analysis (ML and BI), and haplotype networking. The findings documented 19 Eutyphoeus species with CO1 sequences from two biogeographic zones, the Northeast region and the Gangetic plains (5 species of the present study), out of the 28 species reported from India. All species except one form monophyletic clades with strong statistical support. However, E. incommodus split into three lineages, suggesting the existence of cryptic species. Although Eutyphoeus exhibits erratic dispersal patterns, phylogeographic pattern analysis indicates that it is primarily native to its regions of origin. Additionally, the study supports Gates' (1972) hypothesis on the phylogeographic distribution pattern of the genus Eutyphoeus.