Molecular phylogeny and phylogeography of ricefishes (Teleostei: Adrianichthyidae: Oryzias ) in Sri Lanka

Ricefishes of the genus Oryzias occur commonly in the fresh and brackish waters in coastal lowlands ranging from India across Southeast Asia and on to Japan. Among the three species of Oryzias recorded from peninsular India, two widespread species, O. carnaticus and O. dancena, have previously been reported from Sri Lanka based on museum specimens derived from a few scattered localities. However, members of the genus are widespread in the coastal lowlands of Sri Lanka, a continental island separated from India by the shallow Palk Strait. Although recent molecular phylogenies of Adrianichthyidae represent near-complete taxon representation, they lack samples from Sri Lanka. Here, based on sampling at 13 locations representative of the entire geographic and climatic regions of the island's coastal lowlands, we investigate for the first time the molecular phylogenetic relationships and phylogeography of Sri Lankan Oryzias based on one nuclear and two mitochondrial markers. Sri Lankan Oryzias comprise two distinct non-sister lineages within the javanicus species group. One of these is represented by samples exclusively from the northern parts of the island; it is recognized as O. dancena. This lineage is recovered as the sister group to the remaining species in the javanicus group. The second lineage represents a species that is widespread across the island's coastal lowlands. It is recovered as the sister group of O. javanicus and is identified as O. cf. carnaticus. Ancestral-range estimates suggest two independent colonizations of Indian subcontinent and Sri Lanka by widespread ancestral species of Oryzias during two discrete temporal windows: late Miocene and Plio-Pleistocene. No phylogeographic structure is apparent in Sri Lankan Oryzias, suggesting that there are no strong barriers to gene flow and dispersal along the coastal floodplains, as is the case also for other generalist freshwater fishes in the island

Molecular phylogeny and phylogeography of the freshwater-fish genus Pethia (Teleostei: Cyprinidae) in Sri Lanka

Background: Sri Lanka is a continental island separated from India by the Palk Strait, a shallow-shelf sea, which was emergent during periods of lowered sea level. Its biodiversity is concentrated in its perhumid south-western ‘wet zone’. The island’s freshwater fishes are dominated by the Cyprinidae, characterized by small diversifications of species derived from dispersals from India. These include five diminutive, endemic species of Pethia (P. bandula, P. cumingii, P. melanomaculata, P. nigrofasciata, P. reval), whose evolutionary history remains poorly understood. Here, based on comprehensive geographic sampling, we explore the phylogeny, phylogeography and morphological diversity of the genus in Sri Lanka. Results: The phylogenetic analyses, based on mitochondrial and nuclear loci, recover Sri Lankan Pethia as polyphyletic. The reciprocal monophyly of P. bandula and P. nigrofasciata, and P. cumingii and P. reval, is not supported. Pethia nigrofasciata, P. cumingii, and P. reval show strong phylogeographic structure in the wet zone, compared with P. elanomaculata, which ranges across the dry and intermediate zones. Translocated populations of P. nigrofasciata and P. reval in the Central Hills likely originate from multiple sources. Morphological analyses reveal populations of P. nigrofasciata proximal to P. bandula, a narrow-range endemic, to have a mix of characters between the two species. Similarly, populations of P. cumingii in the Kalu basin possess orange fins, a state between the red-finned P. reval from Kelani to Deduru and yellow-finned P. cumingii from Bentara to Gin basins. Conclusions: Polyphyly in Sri Lankan Pethia suggests two or three colonizations from mainland India. Strong phylogeographic structure in P. nigrofasciata, P. cumingii and P. reval, compared with P. melanomaculata, supports a model wherein the topographically complex wet zone harbors greater genetic diversity than the topographically uniform dry-zone. Mixed morphological characters between P. bandula and P. nigrofasciata, and P. cumingii and P. reval, and their unresolved phylogenies, may suggest recent speciation scenarios with incomplete lineage sorting, or hybridization

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