Systematics of the Sri Lankan Water Snakes of the Genus Fowlea Theobald 1868 (Reptilia: Natricidae)

Abstract: Based on phylogenetic and morphological characters, we revise the systematics of the natricid genus Fowlea in Sri Lanka, comprising two morphospecies. The taxonomy of the Sri Lankan populations has long been controversial, and one of the species has, for more than a decade, been listed as Xenochrophis cf. piscator. Although the Sri Lankan populations are morphologically allied to Fowlea piscator in India, they are genetically highly divergent from the eastern Indian F. piscator sensu lato with a p-distance of 9.9–12.3%, and from southwestern Indian Fowlea species with a p-distance of 4.9–11.1% in the mitochondrial cytochrome b gene. Here, we resurrect Müller's (1887) variety, Tropidonotus quincunciatus var. unicolor, as a distinct taxon, elevate it to the species level, and assign it to the genus Fowlea. Therefore, the population so far recognized as X. cf. piscator will be treated hereafter as F. unicolor and we redescribe it and its holotype (by monotypy). We tentatively restrict this species to Sri Lanka and state the possibility of a population in southern India too. The second distinct species, Fowlea asperrima, which is endemic to Sri Lanka, has long been confused with its sympatric congener, F. unicolor comb. nov., and we designate a lectotype and redescribe it herein. Currently, nine species of the genus Fowlea are now recognized, but it is likely that further species (including those regarded as subjective synonyms) remain unrecognized.