Diversity, phylogeny and biogeography of Systomus (Teleostei, Cyprinidae) in Sri Lanka

Sudasinghe, Hiranya; Pethiyagoda, Rohan; Raghavan, Rajeev; Dahanukar, Neelesh; Rüber, Lukas; Meegaskumbura, Madhava (2020). Diversity, phylogeny and biogeography of Systomus (Teleostei, Cyprinidae) in Sri Lanka. Zoologica scripta, 49(6), pp. 710-731. Wiley 10.1111/zsc.12445

Text Sudasinghe et al. 2020_ZoolScr_Diversity phylogeny and biogeography of Systomus in Sri Lanka.pdf - Published Version Restricted to registered users only Available under License Publisher holds Copyright. Download (3MB)

The South and South-East Asian freshwater fish genus Systomus (Cyprinidae) comprises
17 valid species. Six nominal species, including three endemics, have been
reported from Sri Lanka, a continental island separated from India by a shallow-shelf
sea. The species diversity of Systomus on the island has until now not been assessed;
neither has an evaluation been made of their phylogenetic history. Here, based on an
analysis of the nuclear recombination activating protein 1 (rag1), and mitochondrial
cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) gene markers, and a
morphological examination of 143 specimens from 49 locations in Sri Lanka, we reassess
the diversity of Systomus on the island and analyse patterns of their evolution
and biogeography. Divergence-time estimates, based on a substitution rate calibration,
date the basal split between Systomus and its sister group, the Afrotropical small
barbs, to 30.0 Ma (95% highest posterior density: 25.4–35.2 Ma). The species of
Systomus belong to two distinct clades. The first includes the Sri Lankan endemics S.
asoka, S. martenstyni and S. pleurotaenia, which comprise an insular diversification
following the immigration of a common ancestor during the Oligocene. The second,
which includes the remaining species of Indian, Sri Lankan and South-East Asian
Systomus, has a crown age dating to the Late Miocene. Morphological and molecular
species delimitation analyses failed to validate the two nominal species, S. spilurus
and S. timbiri, previously reported from Sri Lanka: both are considered synonyms
of S. sarana, as are the nomina S. chryseus, S. chrysopoma, S. laticeps, S. rufus, S.
pinnauratus and S. subnasutus. Four genetically and geographically discrete lineages
of S. sarana occur in the island, and three in India. Molecular species delimitation
analysis suggests these all belong to a single species, S. sarana. The genetically
distinct Sri Lankan populations of S. sarana result from Plio-Pleistocene dispersal
or vicariance events between India and Sri Lanka—as a result of emergence and inundation of the now submerged isthmus connecting the two landmasses—as well as
autochthonous insular diversification.

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