Phylogeny of freshwater mollusc genus Brotia H. Adams, 1866 (Gastropoda: Pachychilidae) from north-east India

Abstract

The pachychilid genus Brotia H. Adams, 1866, distributed across South and South-East Asia, comprises 46 currently accepted species. Although Brotia has recently been revised, the systematic treatment of the Indian species requires further scrutiny. This study aims to resolve the phylogenetic relationships between Brotia species from north-east India and estimate the divergence using two mitochondrial markers, cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S). Species delimitation analyses have revealed six to nine distinct species in north-east India instead of the single currently known species. We confirm the monophyly of Brotia from the entire distributional range in South and South-East Asia and show that all Indian species form a single clade nested within the South-East Asian radiation. We conclude that Brotia has a South-East Asian origin, with two independent dispersals into India since the early Eocene and through the Oligocene, eventually splitting from ancestors during the late Cretaceous. Further integrative taxonomic research is needed to resolve the taxonomic status of the candidate species delineated herein and reveal the exact number of species in north-east India. This is the first phylogenetic analysis of Brotia from India, significantly improving our understanding of Indian freshwater gastropod fauna.