The loach genus Lepidocephalichthys (Teleostei: Cobitidae) in Sri Lanka and peninsular India: multiple colonizations and unexpected species diversity

Loaches of the genus Lepidocephalichthys are ubiquitous in Peninsular India and the nearby continental-shelf island of Sri Lanka. Four valid species are reported from this region: L. thermalis, a species reported from across this region; L. jonklaasi, confined to rainforests in southern Sri Lanka; L. coromandelensis, from the Eastern Ghats and L. guntea, from the northern Western Ghats of the Indian peninsula. Here, based on collections from 25 locations in 13 river basins in Sri Lanka and 20 locations across India, including a dataset downloaded from GenBank, we present a molecular phylogeny constructed from the mitochondrial cytochrome b (cytb) and cytochrome c oxidase subunit 1 (cox1) sequences. We show that ancestral Lepidocephalichthys colonized Sri Lanka in the late Miocene. Multiple back-migrations to India, as well as colonizations from the mainland, took place in the Plio-Pleistocene. The persistence on the island of L. jonklaasi, an obligatory rainforest associate, suggests that perhumid refugia existed in Sri Lanka throughout this time. Lepidocephalichthys thermalis appears to have colonized the Sri Lankan highlands as recently as the Pleistocene. The data suggest that Lepidocephalichthys thermalis is a species complex in which multiple species remain to be investigated and described, both in India and Sri Lanka.