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

Three nominal species of the killifish genus Aplocheilus are reported from the lowlands of Sri Lanka. Two of these, Aplocheilus dayi and Aplocheilus werneri, are considered endemic to the island, whereas Aplocheilus parvus is reported from both Sri Lanka and Peninsular India. Here, based on a collection from 28 locations in Sri Lanka, also including a dataset of Asian Aplocheilus downloaded from GenBank, we present a phylogeny constructed from the mitochondrial cytochrome b (cytb), mitochondrial cytochrome c oxidase subunit 1 (cox1), and nuclear recombination activating protein 1 (rag1), and investigate the interrelationships of the species of Aplocheilus in Sri Lanka. The endemic Sri Lankan aplocheilid clade comprising A. dayi and A. werneri is recovered as the sister group to the clade comprising A. parvus from Sri Lanka and Aplocheilus blockii from Peninsular India. The reciprocal monophyly of A. dayi and A. werneri is not supported in our molecular phylogeny. A. dayi and A. werneri display strong sexual dimorphism, but species-level differences are subtle, explained mostly by pigmentation patterns. Their phenotypes exhibit a parapatric distribution and may represent locally adapted forms of a single species. Alternatively, the present study does not rule out the possibility that A. dayi and A. werneri may represent an incipient species pair or that they have undergone introgression or hybridization in their contact zones. We provide evidence that the Nilwala-Gin region of southwestern Sri Lanka may have acted as a drought refugium for these fishes.

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

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.

Molecular phylogeny and phylogeography of ricefishes (Teleostei: Adrianichthyidae: Oryzias) in Sri Lanka.

Ricefishes of the genus Oryzias occur commonly in the fresh and brackish waters in coastal lowlands ranging from India across Southeast Asia and on to Japan. Among the three species of Oryzias recorded from peninsular India, two widespread species, O. carnaticus and O. dancena, have previously been reported from Sri Lanka based on museum specimens derived from a few scattered localities. However, members of the genus are widespread in the coastal lowlands of Sri Lanka, a continental island separated from India by the shallow Palk Strait. Although recent molecular phylogenies of Adrianichthyidae represent near-complete taxon representation, they lack samples from Sri Lanka. Here, based on sampling at 13 locations representative of the entire geographic and climatic regions of the island's coastal lowlands, we investigate for the first time the molecular phylogenetic relationships and phylogeography of Sri Lankan Oryzias based on one nuclear and two mitochondrial markers. Sri Lankan Oryzias comprise two distinct non-sister lineages within the javanicus species group. One of these is represented by samples exclusively from the northern parts of the island; it is recognized as O. dancena. This lineage is recovered as the sister group to the remaining species in the javanicus group. The second lineage represents a species that is widespread across the island's coastal lowlands. It is recovered as the sister group of O. javanicus and is identified as O. cf. carnaticus. Ancestral-range estimates suggest two independent colonizations of Indian subcontinent and Sri Lanka by widespread ancestral species of Oryzias during two discrete temporal windows: late Miocene and Plio-Pleistocene. No phylogeographic structure is apparent in Sri Lankan Oryzias, suggesting that there are no strong barriers to gene flow and dispersal along the coastal floodplains, as is the case also for other generalist freshwater fishes in the island.

Molecular phylogeny and phylogeography of the freshwater-fish genus Pethia (Teleostei: Cyprinidae) in Sri Lanka.

BACKGROUND: Sri Lanka is a continental island separated from India by the Palk Strait, a shallow-shelf sea, which was emergent during periods of lowered sea level. Its biodiversity is concentrated in its perhumid south-western 'wet zone'. The island's freshwater fishes are dominated by the Cyprinidae, characterized by small diversifications of species derived from dispersals from India. These include five diminutive, endemic species of Pethia (P. bandula, P. cumingii, P. melanomaculata, P. nigrofasciata, P. reval), whose evolutionary history remains poorly understood. Here, based on comprehensive geographic sampling, we explore the phylogeny, phylogeography and morphological diversity of the genus in Sri Lanka. RESULTS: The phylogenetic analyses, based on mitochondrial and nuclear loci, recover Sri Lankan Pethia as polyphyletic. The reciprocal monophyly of P. bandula and P. nigrofasciata, and P. cumingii and P. reval, is not supported. Pethia nigrofasciata, P. cumingii, and P. reval show strong phylogeographic structure in the wet zone, compared with P. melanomaculata, which ranges across the dry and intermediate zones. Translocated populations of P. nigrofasciata and P. reval in the Central Hills likely originate from multiple sources. Morphological analyses reveal populations of P. nigrofasciata proximal to P. bandula, a narrow-range endemic, to have a mix of characters between the two species. Similarly, populations of P. cumingii in the Kalu basin possess orange fins, a state between the red-finned P. reval from Kelani to Deduru and yellow-finned P. cumingii from Bentara to Gin basins. CONCLUSIONS: Polyphyly in Sri Lankan Pethia suggests two or three colonizations from mainland India. Strong phylogeographic structure in P. nigrofasciata, P. cumingii and P. reval, compared with P. melanomaculata, supports a model wherein the topographically complex wet zone harbors greater genetic diversity than the topographically uniform dry-zone. Mixed morphological characters between P. bandula and P. nigrofasciata, and P. cumingii and P. reval, and their unresolved phylogenies, may suggest recent speciation scenarios with incomplete lineage sorting, or hybridization.

The identity of the exotic Pterygoplichthys sailfin catfishes in Sri Lanka (Teleostei: Loricariidae).

Invasive alien species (IAS) are a major threat to biodiversity and have contributed to population declines in native species worldwide (Vilà et al. 2011; Gurevitch Padilla 2004). IUCN's Invasive Species Specialist Group lists some 80 invasive or potentially invasive species in Sri Lanka, which is part of a global biodiversity hotspot (Myers et al. 2000; Marambe et al. 2011). The major release of aquatic IAS on the island are routed through the ornamental-fish industry (Marambe et al. 2011; Sudasinghe 2016), though a minority represents deliberate, if unplanned, introductions by governmental and non-governmental agencies (Marambe et al. 2011).

Evolution of Sri Lanka's Giant Danios (Teleostei: Cyprinidae: Devario): Teasing apart species in a recent diversification.

The small, colourful freshwater fishes of the cyprinid genus Devario are among the many vertebrate groups that appear to have diversified on Sri Lanka, a continental Indian Ocean island, which is part of the Western Ghats-Sri Lanka Biodiversity Hotspot. Despite Sri Lanka having been connected with India via a wide isthmus intermittently until the Plio-Pleistocene and almost continuously since then, during sea-level low-stands, the number of species of Devario on Sri Lanka is comparable with that on the Indian Peninsula, some 25 times its size. Here, from a sampling of 27 Devario populations across Sri Lanka's major river basins and climatic zones, we present and analyze a phylogeny based on mitochondrial and nuclear DNA data. We show that five species of Devario occur on the island, all but one of which are endemic: Devario malabaricus is widespread throughout the lowlands and parts of central hills of Sri Lanka and southern India. A new narrow-range endemic, here described as D. memorialis sp. nov., was discovered in a remnant rainforest habitat at Aranayake (Ma Oya basin) in this study. It is immediately distinguished from Sri Lankan congeners by having only 8 (vs 9-12) branched dorsal-fin rays and by uncorrected pairwise genetic distances of more than 4.0% and 7.8% for cytochrome c oxidase subunit 1 and cytochrome b, respectively. Our results provide strong support for the monophyly of the entire Sri Lankan diversification of Devario. Divergence-timing analysis suggests the common ancestor dispersed to the island in the late Miocene, with the insular diversification in the island's south-western wet zone taking place during the Plio-pleistocene. There are signs of gene flow between the Indian and Sri Lankan populations of D. malabaricus until the late Pleistocene. Phylogenetic and haplotype-network analyses suggest basin-centric phylogeographic structure within the endemic species; D. malabaricus, however, shows little such structure in the island. Molecular and morphological analyses failed to identify D. annnataliae and D. udenii confidently as distinct species: they are considered synonyms of D. micronema. The morphological variation observed within D. micronema is likely attributable to polymorphism. The discordance between the mitochondrial and nuclear phylogenies for some samples of Devario in the present study suggest signs of mitochondrial introgression.

Unexpected species diversity within Sri Lanka's snakehead fishes of the Channa marulius group (Teleostei: Channidae).

The taxonomic status of the large snakeheads of the Channa marulius group that occur in Sri Lanka is reviewed and clarified. Two species are recognized from the island, based on both morphological and molecular (cytochrome c oxidase subunit 1: cox1) differentiation: C. marulius Hamilton from the northern dry zone and C. ara Deraniyagala from the middle and lower regions of the Mahaweli basin. Channa ara is endemic to Sri Lanka and can be distinguished from its Marulius group congeners, C. marulius, C. aurolineata and C. auroflammea, by having fewer dorsal- and anal-fin rays, fewer lateral-line scales and fewer vertebrae; from C. marulioides by a different adult colour pattern; and from C. pseudomarulius by having more vertebrae. At the cox1 barcoding locus, Channa ara is at least 3.6% genetically different from C. marulius, and at least 8% different from the other described species in the group. Specimens collected from the southwestern wet zone in Sri Lanka are a puzzling third component of the Marulius group's diversity, uncovered in this study, and identified here as C. cf. ara. Whilst genetically more similar to C. marulius, C. cf. ara possesses fewer dorsal- and anal-fin rays, fewer lateral-line scales and fewer vertebrae and is therefore morphologically more similar to C. ara. Channa ara can be distinguished from C. cf. ara, however, by differences in circumpeduncular scale count, adult colour pattern, and by an uncorrected pairwise genetic distance of 3.7% in cox1 sequences. A neotype is designated for Ophicephalus marulius ara Deraniyagala.

The identity of the Sri Lankan Amblypharyngodon (Teleostei, Cyprinidae).

Morphological and molecular analyses of specimens representative of the geographic range of the cyprinid genus Amblypharyngodon in Sri Lanka suggest the presence of only a single species in the island, for which the name Amblypharyngodongrandisquamis Jordan & Starks, 1917, is available. Amblypharyngodongrandisquamis is a species endemic to Sri Lanka, distributed across the lowlands of both of the island's main climatic zones. It is distinguished from all other species of Amblypharyngodon, including the three species recorded from peninsular India (A.mola, A.microlepis, and A.melettinus), by a suite of characters that includes a body depth of 26.9-31.2% of the standard length (SL), 42-56 scales in the lateral series (of which usually 8-16 are pored), 20-24 circumpeduncular scales, 14-17 scale rows between the origins of the dorsal and pelvic fins, a dorsal-fin height of 21.1-27.6% SL, 18-19 caudal vertebrae and an eye diameter of 22.7-30.5% of the head length. Amblypharyngodongrandisquamis differs from A.melettinus and A.mola by uncorrected pairwise genetic distances of more than 9% and 6%, respectively, for the mitochondrial cytochrome oxidase subunit 1 (COI) gene.

A commentary on the taxonomic review of Sri Lankan Devario by Batuwita et al. 2017 (Teleostei: Danionidae).

We address several problems arising from 'A review of the genus Devario in Sri Lanka (Teleostei: Cyprinidae), with description of two new species', a paper authored by S. Batuwita, M. de Silva and S. Udugampola and published in 2017 in the journal FishTaxa (2(3): 156-179). The neotypes they designate for Perilampus malabaricus Jerdon and Perilampus mysoricus Jerdon are inconsistent with article 75.3 of the International Code of Zoological Nomenclature ('the Code') and are hence invalid. Devario udenii, which they describe as a new species, is shown to be indistinguishable from D. micronema sensu Batuwita et al. The characters by which they distinguish another new species, D. annnataliae, are shown to be self-contradictory, making it impossible to distinguish from its congeners; it is treated as a species inquirendum. The diagnoses provided for D. malabaricus, D. micronema and D. monticola are ambiguous and self-contradictory, rendering them unusable. Much of the material examined, stated to be in the collection of the National Museum of Sri Lanka, is not deposited in that institution: such material as is deposited is inconsistent with the specimen data published by Batuwita et al.

A new species of Schistura (Teleostei: Nemacheilidae) from the south-western lowlands of Sri Lanka.

Schistura scripta, new species, is described from Nakiyadeniya in the south-western lowlands of Sri Lanka. It can be distinguished from all other congeners from Sri Lankan and peninsular India by the combination of the following characters: an incomplete lateral line with 53-76 pores, ending beneath the dorsal-fin base or slightly beyond; 7-13 post-dorsal bars; 7½ branched dorsal-fin rays; absence of an axillary pelvic lobe; and absence of a suborbital flap.

A review of the genus Labeo (Teleostei: Cyprinidae) in Sri Lanka.

The taxonomy of the three native taxa assigned to the genus Labeo (L. dussumieri, L. fisheri and L. porcellus lankae) in Sri Lanka is reviewed. The population hitherto identified as L. dussumieri in Sri Lanka is shown to be a distinct species, here named L. heladiva. Labeo heladiva, new species, has a wide distribution in the low and mid-elevations of the island and is distinguished from its Indian congeners by the combination of having two pairs of barbels; 12-13 branched dorsal-fin rays; lateral line with 44-51 scales; ½8-½9+1+6-7 scales in transverse series; and 19-22 circumpeduncular scales. It differs from its closest relative, L. dussumieri, principally by having 44-51 vs. 50-60 lateral-line scales, 19-22 vs. 22-27 circumpeduncular scales, and by uncorrected pairwise genetic distances of 1.27-2.22% and 1.88-2.91% for the two mitochondrial genes COI and cytb, respectively. Labeo fisheri, which is endemic to the upper reaches of the Mahaweli River basin in the Knuckles mountain range and the central hills in the vicinity of Kandy, is distinguished from Indian congeners by having (in combination) only a single pair of barbels; dorsal fin with 10-12 branched rays; lateral line with 37-39 scales; 7+1+4½-6 scales in transverse series; and 17-20 circumpeduncular scales. Labeo lankae is recognized as a valid species endemic to Sri Lanka. Long suspected to have become extinct, or known only from spurious records, an extant population is reported from the northern dry zone of the island. Labeo lankae is the sister species of L. porcellus of peninsular India; it can be distinguished from its congeners by having, in combination, 10-12 branched dorsal-fin rays; 36-39 lateral-line scales; ½8+1+5-6½ scales in transverse series; and 21-24 circumpeduncular scales. It differs from L. porcellus principally by having ½8 (vs. ½6-½7) scales between the origin of the dorsal fin and the lateral line, 21-24 (vs. 20-21) circumpeduncular scales and uncorrected pairwise genetic distances of 1.27% and 1.41% for the mitochondrial genes COI and cytb, respectively. The three species of Labeo in Sri Lanka do not form a monophyletic group.

Undocumented translocations spawn taxonomic inflation in Sri Lankan fire rasboras (Actinopterygii, Cyprinidae).

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.

Ompok argestes, a new species of silurid catfish endemic to Sri Lanka (Teleostei: Siluridae).

Ompok argestes, a new species of silurid catfish, is described from the southwestern lowlands of Sri Lanka. The new species is distinguished from all other species of Ompok in the Indian subcontinent by a combination of the following characters: body color pattern mottled; predorsal profile uniformly convex; maxillary barbels reach or extend slightly beyond base of dorsal fin; eye diameter 14.2-17.1% head length (HL); body depth at anus 19.8-22.3% standard length (SL); head width 14.3-16.8% SL; caudal peduncle depth 5.6-6.5% SL. Callichrous ceylonensis Günther is shown to be a valid species that is apparently restricted to Sri Lanka, distinguished by a combination of the following characters: distinct concavity in predorsal profile; origin of pelvic fin beneath or slightly posterior to the origin of the dorsal fin; maxillary barbels 108-166 % HL; mandibular barbels 16.1-33.7 % HL; and 58-66 anal-fin rays.

Redescription of Pethia melanomaculata (Teleostei: Cyprinidae) from Sri Lanka.

The name Pethia melanomaculata (Deraniyagala) is available for the Sri Lankan fish previously referred to P. ticto, being distinguished from its Indian congeners by the combination of the following characters; having ½4/1/3½ scales in transverse line on body; body depth 32.4-41.5% of standard length (SL); head length (HL) 26.1-29.2% of SL; snout length 25.3-35.6% of HL; eye diameter 24.4-31.9% of HL; a small black humeral spot on lateral-line scales 3 or 4; a black spot on caudal peduncle, on scales 16-18 of the lateral line series; 3 unbranched dorsal-fin rays, the last one strongly serrated, with 8-11 serrae.