[Ichthyology • 2018] Rasboroides vaterifloris & P. pallidus • Undocumented Translocations Spawn Taxonomic Inflation in Sri Lankan Fire Rasboras (Actinopterygii, Cyprinidae) ---ScRaBBlE

(A–D) Rasboroides vaterifloris Deraniyagala, 1930
(E–J) Rasboroides pallidus Deraniyagala, 1958

in Sudasinghe, Herath, Pethiyagoda & Meegaskumbura, 2018. 

DOI: 10.7717/peerj.6084

Abstract

A recent (2013) taxonomic review of the freshwater-fish genus Rasboroides, which is endemic to Sri Lanka, showed it to comprise four species: R. vaterifloris, R. nigromarginatus, R. pallidus and R. rohani. Here, using an integrative-taxonomic analysis of morphometry, meristics and mitochondrial DNA sequences of cytochrome b (cytb) and cytochrome oxidase subunit 1 (coi), we show that R. nigromarginatus is a synonym of R. vaterifloris, and that R. rohani is a synonym of R. pallidus. The creation and recognition of unnecessary taxa (‘taxonomic inflation’) was in this case a result of selective sampling confounded by a disregard of allometry. The population referred to R. rohani in the Walawe river basin represents an undocumented trans-basin translocation of R. pallidus, and a translocation into the Mahaweli river of R. vaterifloris, documented to have occurred ca 1980, in fact involves R. pallidus. A shared haplotype suggests the latter introduction was likely made from the Bentara river basin and not from the Kelani, as claimed. To stabilize the taxonomy of these fishes, the two valid species, R. vaterifloris and R. pallidus, are diagnosed and redescribed, and their distributions delineated. We draw attention to the wasteful diversion of conservation resources to populations resulting from undocumented translocations and to taxa resulting from taxonomic inflation. We argue against translocations except where mandated by a conservation emergency, and even then, only when supported by accurate documentation.

Figure 4: Live color pattern variation in A–D, Rasboroides vaterifloris; E–J, R. pallidus.
(A) topotypes of R. vaterifloris, Kalu basin, Gilimale; (B–D) topotypes of population identified as R. nigromarginatus by Batuwita, De Silva & Edirisinghe (2013), Kalu basin, Athwelthota; (E) Bentara basin, Pitigala; (F) topotypes of population identified as R. rohani by Batuwita, De Silva & Edirisinghe (2013), Walawe basin, Suriyakanda; (G) Bentara basin, Yagirala; (H) Gin basin, Udugama; (I) Bentara basin, Yagirala; (J) Bentara basin, Pitigala. (A, B, D, E, F, G, H) males; (C, I, J) females. Specimens not collected.

 Live color pattern variation in Rasboroides vaterifloris.
(A) topotypes of R. vaterifloris, Kalu basin, Gilimale; (B–D) topotypes of population identified as R. nigromarginatus by Batuwita, De Silva & Edirisinghe (2013), Kalu basin, Athwelthota.

 (A, B, D) males; (C) females. Specimens not collected.

Rasboroides vaterifloris Deraniyagala, 1930

Rasbora vaterifloris Deraniyagala, 1930: 129

Rasbora nigromarginata Meinken, 1957: 65–68

Rasbora vaterifloris var. nigromarginatus Deraniyagala, 1958: 137

Rasboroides nigromarginatus (Meinken, 1957): Batuwita, De Silva & Edirisinghe, 2013

Diagnosis. Males of Rasboroides vaterifloris can be distinguished from males of R. pallidus by having the unbranched rays of dorsal, anal, pectoral and pelvic fins black along their entire length, more distinctly evident in the last unbranched ray of the dorsal fin (vs. the mentioned rays being the same color as other rays; in preserved specimens, interradial membranes of dorsal, anal, pelvic and pectoral fins with distinct, scattered melanophores (vs. absent or vaguely present only around the beginning). Females of R. vaterifloris have a lesser body depth (27.2–31.9% SL vs. 31.7–35.5) than those of R. pallidus.

Live color pattern variation in Rasboroides  pallidus. (E) Bentara basin, Pitigala; (F) topotypes of population identified as R. rohani by Batuwita, De Silva & Edirisinghe (2013), Walawe basin, Suriyakanda; (G) Bentara basin, Yagirala; (H) Gin basin, Udugama; (I) Bentara basin, Yagirala; (J) Bentara basin, Pitigala.

 (E, F, G, H) males; (I, J) females. Specimens not collected.

Rasboroides pallidus Deraniyagala, 1958

Rasbora vaterifloris pallida Deraniyagala, 1958: 136.

Rasbora vaterifloris ruber Deraniyagala, 1958: 136.

Rasbora vaterifloris rubioculis Deraniyagala, 1958: 136.

Rasboroides rohani Batuwita, De Silva & Edirisinghe, 2013

Diagnosis. The males of Rasboroides pallidus can be distinguished from the males of R.  vaterifloris by having the unbranched rays of dorsal, anal, pectoral and pelvic fins the same color as other branched rays (vs. black along their entire length); in preserved specimens, interradial membranes of dorsal, anal, pelvic and pectoral fins without distinct scattered melanophores throughout or with only minute, vague melanophores only around the beginning (vs. melanophores distinctly present). The females of R. pallidus have greater body depth (31.7–35.5% SL vs. 27.2–31.9) than females of R. vaterifloris.

Conclusion: 

As a freshwater-fish genus endemic to Sri Lanka and restricted largely to streams draining the island’s dwindling rainforest estate, Rasboroides attracts considerable conservation attention. The National Red List (MOE, 2012) treats ‘R. nigromarginatus’ as Critically Endangered and R. vaterifloris as Endangered. The synonymy of these two nominal species demonstrated here allows their ranges to be combined, widening their extent of occurrence and area of occupancy and hence potentially lowering the threat-status of R. vaterifloris. Although ‘R. rohani’ has not as yet been assessed for conservation purposes, its restriction to a small population at a single locality would almost certainly have caused it to be ranked as Critically Endangered. Given that we show here that it represents only an undocumented translocation of R. pallidus, its population is now only of marginal conservation concern. Indeed, of the two valid species of Rasboroides, R. pallidus enjoys the wider range and hence warrants less conservation concern, especially given its successful translocation to two river basins (Mahaweli and Walawe) in which it did not previously occur.

In describing ‘R. rohani’ as a new species, Batuwita, De Silva & Edirisinghe (2013) were misled by apparently collecting only the largest specimens for their sample while neglecting to account for allometric growth. It is additionally regrettable that the type series of ‘R. rohani’ designated by these authors cannot be identified in the collection of the National Museum of Sri Lanka, in which it was stated to be deposited.

Both translocations referred to in this paper were made by well-meaning citizens but without the safeguards that should apply in such cases. Perhaps most egregiously, no records were published of the rationale for translocation or the precise identity and origin of the source population. We urge that any future attempts to introduce species to novel habitats be guided by IUCN/SSC (2013) and that the intentional release or introduction of species without legal sanction be prohibited in Sri Lanka.

Hiranya Sudasinghe, Jayampathi Herath, Rohan Pethiyagoda and Madhava Meegaskumbura. 2018. Undocumented Translocations Spawn Taxonomic Inflation in Sri Lankan Fire Rasboras (Actinopterygii, Cyprinidae). PeerJ. 6:e6084.  DOI: 10.7717/peerj.6084

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