Morphological and genetic evidence for multiple evolutionary distinct lineages in the endangered and commercially exploited red lined torpedo barbs endemic to the Western Ghats of India.

Lijo John,Palakkaparambil Hamsa Anvar Ali,Siby Philip,Agostinho Antunes,Rajeev Raghavan,Josin Tharian,Neelesh Dahanukar

doi:10.1371/journal.pone.0069741

Abstract

Red lined torpedo barbs (RLTBs) (Cyprinidae: Puntius) endemic to the Western Ghats Hotspot of India, are popular and highly priced freshwater aquarium fishes. Two decades of indiscriminate exploitation for the pet trade, restricted range, fragmented populations and continuing decline in quality of habitats has resulted in their ‘Endangered’ listing. Here, we tested whether the isolated RLTB populations demonstrated considerable variation qualifying to be considered as distinct conservation targets. Multivariate morphometric analysis using 24 size-adjusted characters delineated all allopatric populations. Similarly, the species-tree highlighted a phylogeny with 12 distinct RLTB lineages corresponding to each of the different riverine populations. However, coalescence-based methods using mitochondrial DNA markers identified only eight evolutionarily distinct lineages. Divergence time analysis points to recent separation of the populations, owing to the geographical isolation, more than 5 million years ago, after the lineages were split into two ancestral stocks in the Paleocene, on north and south of a major geographical gap in the Western Ghats. Our results revealing the existence of eight evolutionarily distinct RLTB lineages calls for the re-determination of conservation targets for these cryptic and endangered taxa.

Highlights

Of the 563 million species on earth, only 1.5 million have names [1]
Being a taxonomically diverse group exhibiting a remarkable and fascinating array of morphologies, cypriniform fishes present many challenges to systematists and evolutionary biologists [15,16]. Such challenges are severe in biogeographic ‘Hotspots’ such as the Western Ghats (WG) of India, where endemic lineages have evolved in several taxa due to extended geographical isolation [17,18,19]
The multivariate analysis and the GMYC methods support those eight clades, and identify others in addition, while the fixed distance threshold methods support seven out of the eight clades identified by Bayesian and the ML methods. By integrating both morphological and molecular results we propose that Red lined torpedo barbs (RLTBs) consists of at least eight evolutionarily distinct lineages, i.e., the number of distinct populations identified with high probabilities and corroborated by both morphological and molecular methods

Summary

Introduction

Of the 563 million species on earth, only 1.5 million have names [1]. Accelerating the description of unknown biodiversity continues to be a major challenge as extinction rates increase [2] and modern taxonomy is far from reaching a scientific consensus on species concept and delimitation [3,4]. Distinctive units, such as evolutionarily significant units (ESUs) or designatable units (DUs), which are appropriate targets for conservation, may remain undetected for long periods of time [5] This is a critical impediment for regions harboring exceptionally high biodiversity, that face a high risk of anthropogenic impacts [6] and among speciose yet poorly known taxa, such as reptiles [7,8,9] and freshwater fishes [10,11,12,13]. The order Cypriniformes is a monophyletic group of primary freshwater fishes containing over 3500 species, with a wide distribution in North America, Europe, Africa and Asia [14,15] These fishes are an essential protein source for many societies, are highly valued in recreational fisheries and constitute a major component of the tropical fish trade [12]. Such challenges are severe in biogeographic ‘Hotspots’ such as the Western Ghats (WG) of India, where endemic lineages have evolved in several taxa due to extended geographical isolation [17,18,19]

Results

Discussion

Conclusion