A molecular phylogeny of the genus <i>Laubuka</i> (Teleostei: Cyprinidae) in Sri Lanka reveals multiple origins and a cryptic species

The freshwater-fish genus <i>Laubuka</i> contains ∼13 species distributed through the lowlands of tropical South and South-east Asia. Four of these species (<i>Laubuka lankensis</i>, <i>L. varuna</i>, <i>L. ruhuna</i>, and <i>L. insularis</i>) are reported as endemic to Sri Lanka, a remarkable datum given the island’s small size. We sampled populations of <i>Laubuka</i> at 56 locations in 14 of the island’s principal river basins and analysed their morphological, meristic, phylogenetic, and phylogeographic relationships using the mitochondrial genes <i>cytochrome b</i> and <i>cytochrome c oxidase subunit 1</i> and the nuclear <i>recombination activating protein 1</i>. We investigated the geographic structure, and delineated species using molecular species delimitation methods and morphological analysis within the general lineage concept of species. Molecular and morphological analyses failed to identify <i>L. ruhuna</i> and <i>L. insularis</i> as distinct species; we show them to be synonyms of <i>L. varuna</i> and <i>L. lankensis</i>, respectively. Taxonomic inflation in previous literature is attributed as a result of limited sampling and negligence of size allometry. Additionally, a third, cryptic species discovered in this study is described as <i>L. hema</i> sp. nov. which is evidently confined to the headwaters of the Gal basin in eastern Sri Lanka. Phylogenetic and haplotype network analyses suggest phylogeographic structure within both the southwest-endemic <i>L. varuna</i> and the dry-zone endemic <i>L. lankensis</i>, but the former shows strong phylogeographic structure between adjacent basins. The Sri Lankan species of <i>Laubuka</i> do not form a monophyletic group: they stem from two dispersal or vicariance events, one involving the lineage that led to <i>L. varuna</i> in south-western Sri Lanka, and the other, of [<i>L. lankensis</i> + <i>L. hema</i>] in the dry zone. http://zoobank.org/urn:lsid:zoobank.org:pub:D2A29329-E0E7-447E-B316-81049212CCCB http://zoobank.org/urn:lsid:zoobank.org:act:920E5DC0-CEDC-4243-98C7-12CCF829CBCD