Molecular phylogeny unveils hidden diversity of hillstream loaches (Cypriniformes: Cobitoidea) in the northern Western Ghats of India

The diversity of hillstream loaches in the northern part of the Western Ghats region of India was studied for the first time using two mitochondrial genes, cytochrome oxidase subunit I and cytochrome b. Phylogenetic analysis revealed monophyletic groups corresponding to the genera Indoreonectes, Paracanthocobitis, Nemacheilus, Schistura and Nemachilichthys (family Nemacheilidae), and Balitora, Lepidocephalichthys and Botia (families Balitoridae, Cobitidae and Botiidae respectively). While there was little inter-population genetic divergence for genera such as Nemacheilus, Nemachilichthys, Balitora and Botia, each of which harbored a single species, there were distinct clades observed for Indoreonectes, Paracanthocobitis, Schistura and Lepidocephalichthys, which were supported through species delimitation by Poisson Tree Processes, Generalized Mixed Yule Coalescence and barcode gap analysis. We show that Indoreonectes evezardi, currently considered to be a wide-ranging species, is a 'complex' comprising of several genetically distinct clades indicating the presence of undescribed species. Further, we also suggest a possibility of hidden species diversity within the genera Paracanthocobitis, Schistura and Lepidocephalichthys. Based on different species delimitation methods, we suggest that there could be between 23 and 31 species of loaches belonging to eight genera and four families in the northern part of the Western Ghats of India. Our study substantially contributes to the understanding of the diversity and conservation status of loaches in this region.