 |
in Sudasinghe, Ranasinghe, Herath, ... et Meegaskumbura, 2021. |
Abstract
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. melanomaculata, 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.
Keywords: Smiliogastrinae, Morphology, Barb, Biodiversity hotspot, India
Conclusions:
Despite Pethia being a widespread freshwater fish genus in South Asia, most studies so far have focused on taxonomy, with little or no emphasis on geographic sampling focusing on phylogeographic work. We focus on phylogeny, phylogeography, using nuclear DNA and mitochondrial DNA markers, and compare these results with morphology of the group. Polyphyly in Sri Lankan Pethia suggests two or three colonizations from mainland India. Strong phylogeographic structure suggests that the topographically complex wet zone harbors greater genetic diversity than the more uniform dry-zone. Mixed morphological characters between some of the taxa, and their unresolved phylogenies, may suggest recent speciation events with incomplete lineage sorting, or hybridization. The knowledge generated will not only form a foundation for systematics work, but also will help in understanding the processes of speciation and patterns of distribution, allowing for informed conservation of this charismatic group of fishes.
Hiranya Sudasinghe, Tharindu Ranasinghe, Jayampathi Herath, Kumudu Wijesooriya, Rohan Pethiyagoda, Lukas Rüber and Madhava Meegaskumbura. 2021. Molecular Phylogeny and Phylogeography of the Freshwater-fish Genus Pethia (Teleostei: Cyprinidae) in Sri Lanka. BMC Ecology and Evolution. 21: 203. DOI: 10.1186/s12862-021-01923-5