Molecular phylogenetics of Sri Lankan Ichthyophis (Amphibia: Gymnophiona: Ichthyophiidae), with discovery of a cryptic species

Based on previous morphological analyses, the caecilian amphibian (Gymnophiona) fauna of Sri Lanka has been considered to consist of three endemic species of the ichthyophiid genus Ichthyophis, two of which have a lateral yellow stripe. We examined the relationships of Sri Lankan caecilians using partial sequences of mitochondrial 12S and 16S rRNA and cytochrome b genes for 18 Sri Lankan Ichthyophis from 14 localities. Based on the latest keys, these 18 samples represent one striped (I. glutinosus) and one unstriped (L orthoplicatus) species. Sequences for these samples were aligned against previously reported sequences for Indian and Southeast Asian Ichthyophis, and analysed using parsimony, maximum likelihood, distance and Bayesian methods. Results from all methods are in close agreement. Inferred trees strongly support the hypothesis that Sri Lankan caecilians are monophyletic, though their relationships to other Asian caecilians are unclear. While most of the striped specimens that key out as I. glutinosus comprise a clade, a small subset from a single locality are robustly recovered as more closely related to the unstriped I. orthoplicatus. These individuals are interpreted as a possibly new, morphologically cryptic species. The I. glutinosus clade is the most widespread among our samples, and it contains some weakly supported, but consistently recovered hierarchical structure. Most notably, all specimens from the southwestern corner of Sri Lanka comprise a clade, possibly representing a relatively recent dispersal from the central highlands.