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Issue: Vol. 5785 No. 3: 31 Mar. 2026
Type: Article
Published: 2026-03-31
DOI: 10.11646/zootaxa.5785.3.6
Page range: 527-543
Abstract views: 23
PDF downloaded: 0

Population genetic structure and phylogeography of two South Asian Killifishes, Aplocheilus blockii and A. parvus

Department of Zoology; PSGR Krishnammal College for Women; Coimbatore; India
Department of Life Sciences; School of Natural Sciences; Shiv Nadar Institution of Eminence; Delhi-NCR; India
Wildlife Heritage Trust; 117; Park Road; Colombo 5; Sri Lanka; Division of Evolutionary Ecology; Institute of Ecology and Evolution; University of Bern; 3012 Bern; Switzerland; Naturhistorisches Museum Bern; Bernastrasse; 15; 3005 Bern; Switzerland
Department of Zoology; PSGR Krishnammal College for Women; Coimbatore; India
Wildlife Heritage Trust; 117; Park Road; Colombo 5; Sri Lanka
Department of Zoology; Faculty of Science; University of Peradeniya; Peradeniya; Sri Lanka
Faculty of Ocean Science and Technology; Kerala University of Fisheries and Ocean Studies (KUFOS); Kochi; India
Faculty of Ocean Science and Technology; Kerala University of Fisheries and Ocean Studies (KUFOS); Kochi; India
Guangxi Key Laboratory of Forest Ecology & Conservation; College of Forestry; Guangxi University; Nanning; P. R. China
Department of Fisheries Resource Management; Kerala University of Fisheries and Ocean Studies (KUFOS); Kochi; India
Pisces asian rivulines haplotype

Abstract

The identity and taxonomic status of the South Asian killifishes Aplocheilus blockii and A. parvus has often been debated, with the latter name considered a junior synonym of the former. To understand whether topotypic A. blockii and A. parvus, and populations across a wider distribution range in peninsular India and Sri Lanka, signal genetic structuring, and to help resolve the ambiguous taxonomy of these nominal species, we studied their population genetics and phylogeography based on the partial mitochondrial cytochrome c oxidase subunit 1 (cox1) gene marker. Phylogenetic analysis revealed that Aplocheilus blockii and A. parvus form two distinct, reciprocally monophyletic sister clades, the former of which is restricted to India while the latter is shared between southern Peninsular India and Sri Lanka. The maximum uncorrected intra-specific cox1 genetic distance was 1.5% for A. blockii and 0.7% for A. parvus, while minimum inter-specific genetic distance between the two species was 2.4%, suggesting that a narrow genetic gap, between 1.5 to 2.4%, separates the species. Despite the low genetic divergence between these sister taxa, they are readily distinguished morphologically by the pattern of iridescent scales on the side of the body. While A. blockii has continuous rows of iridescent scales on the lateral surface, giving an impression of horizontal iridescent lines, iridescence on the lateral surface of A. parvus is restricted to alternate scales, giving an impression of vertical iridescent lines. The median-joining genetic network revealed 37 haplotypes in A. blockii and 32 haplotypes in A. parvus. No haplotypes of A. parvus are shared between southern India and Sri Lanka. Analysis of molecular variance confirmed that there is significant population genetic structuring between the two species and their populations. We discuss genetic diversity and structuring in A. blockii and A. parvus in the context of the physiography of the southern Indian peninsula and Sri Lanka, as well as the historical biogeography of the region, and review implications for the taxonomy of south Asian killifishes.

 

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How to Cite

Sreesha, G., Dahanukar, N., Sudasinghe, H., Sasikala, G., Ranasinghe, T., Wijesooriya, K., Anoop, V.K., Thomas, L., Meegaskumbura, M. & Raghavan, R. (2026) Population genetic structure and phylogeography of two South Asian Killifishes, Aplocheilus blockii and A. parvus. Zootaxa, 5785 (3), 527–543. https://doi.org/10.11646/zootaxa.5785.3.6