Biogeography and evolutionary history of Puntius sensu lato (Teleostei: Cyprinidae) in Sri Lanka

Abstract

Sri Lanka’s biota is derived largely from Southeast Asian lineages which immigrated via India following its early-Eocene contact with Laurasia. The island is now separated from southeastern India by the 30 km wide Palk Strait which, during sea-level low-stands, was bridged by the 140 km-wide Palk Isthmus. Consequently, biotic ingress and egress were mediated largely by the climate of the isthmus. Because of their dependence on perennial aquatic habitats, freshwater fish are useful models for biogeographic studies. Here we investigate the timing and dynamics of the colonization of—and diversification on—Sri Lanka by a group of four closely-related genera of cyprinid fishes (Puntius sensu lato). We construct a molecular phylogeny based on two mitochondrial and two nuclear gene markers, conduct divergence timing analyses and ancestral-range estimations to infer historical biogeography, and use haplotype networks to discern phylogeographic patterns. The origin of Puntius s.l. is dated to ~ 20 Ma. The source of diversification of Puntius s.l. is Sri Lanka-Peninsular India. Species confined to perhumid rainforests show strong phylogeographic structure, while habitat generalists show little or no such structure. Ancestral range estimations for Plesiopuntius bimaculatus and Puntius dorsalis support an ‘Out of Sri Lanka’ scenario. Sri Lankan Puntius s.l. derive from multiple migrations across the Palk Isthmus between the early Miocene and the late Pleistocene. Species dependent on an aseasonal climate survived aridification in rainforest refugia in the island’s perhumid southwest and went on to recolonize the island and even southern India when pluvial conditions resumed. Our results support an historical extinction of Sri Lanka’s montane aquatic fauna, followed by a recent partial recolonization of the highlands, showing also that headwater stream capture facilitated dispersal across basin boundaries.

Phylogenetic and phylogeographic insights into Sri Lankan killifishes (Teleostei: Aplocheilidae)

“…Both haplotype and nucleotide diversities were greater in the southwestern endemics of the Dayi‐Werneri group compared with the widespread generalist A. parvus . This is consistent with the general phylogeographic pattern observed in Sri Lankan freshwater fishes, where southwestern endemics harbor greater genetic diversity, albeit within a narrower distribution, compared with their more widespread congeners (Sudasinghe et al, 2020a; Sudasinghe et al, 2020b; Sudasinghe et al, 2020c; Sudasinghe et al, 2020d; Sudasinghe et al, 2021b; Sudasinghe et al, 2023a).…”

“…It is noteworthy that lineage 1 of the Dayi‐Werneri group, which consists entirely of the A. werneri phenotype, is the sister group to the other two lineages and confined to the Nilwala basin. Several previous studies have suggested that southern Sri Lankan rainforests may have served as freshwater‐fish refugia in periods of drought, such as those associated with glacial maxima (Pethiyagoda & Sudasinghe, 2021; Sudasinghe et al, 2020c; Sudasinghe et al, 2020d; Sudasinghe et al, 2021a; Sudasinghe et al, 2023a; Sudasinghe et al, 2023b). Such an inference is supported also by the rag1 haplotypes H1 and H2 being confined to the Nilwala, with H6 being shared by the Nilwala and Gin.…”