Species without borders: the diversification of giant danios in Sri Lanka (Teleostei, Danionidae, Devario)

The five species of Devario in Sri Lanka form a monophyletic insular diversification. Devario memorialis, D. micronema and D. pathirana are specialists that inhabit rainforest foothill streams, while D. altus sp. nov., is confined to a single montane site (1580 m asl). Finally, D. malabaricus, a generalist species associated with open lentic and lotic habitats, is widely distributed from ~ 0–1500 m asl.

The taxonomy of these species has been handicapped by a high degree of intraspecific phenetic variation. Here we construct a phylogeny of, and haplotype networks for, Sri Lankan Devario using a molecular dataset derived from the cox 1 and cytb mitochondrial DNA markers and the rag 1 and irdp nuclear DNA markers representative of all five species. We compare the mitochondrial and nuclear phylogenies for evidence of discordance, showing that D. malabaricus appears to have hybridized with all the other species, except D. memorialis, in their contact zones.

The phenotype of D. malabaricus varies with elevation as a cline, partly converging on the phenotype of D. altus sp. nov., possibly through introgression with D. altus sp. nov. or adaptation to hill-stream habitats. Through a morphological analysis of 363 voucher specimens representative of all five species, we characterize the species, thereby stabilizing their taxonomy.