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Corresponding author: Sébastien Lavoué ( microceb@hotmail.com ) Academic editor: Nicolas Hubert
© 2020 Sébastien Lavoué, Siti Zafirah Ghazali, Jamsari Amirul Firdaus Jamaluddin, Siti Azizah Mohd Nor, Khaironizam Md. Zain.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lavoué S, Zafirah Ghazali S, Amirul Firdaus Jamaluddin J, Azizah Mohd Nor S, Zain KMd (2020) Genetic evidence for the recognition of two allopatric species of Asian bronze featherback Notopterus (Teleostei, Osteoglossomorpha, Notopteridae). Zoosystematics and Evolution 96(2): 449-454. https://doi.org/10.3897/zse.96.51350
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The fish genus Notopterus Lacepède, 1800 (Notopteridae) currently includes only one species, the Asian bronze featherback Notopterus notopterus (Pallas, 1769). This common freshwater species is widely distributed in the Oriental region, from the Indus basin in the west, the Mekong basin in the east and Java Island in the south. To examine the phylogeographic structure of N. notopterus across its range, we analysed 74 publicly available cytochrome oxidase I (COI) sequences, 72 of them determined from known-origin specimens, along with four newly-determined sequences from Peninsular Malaysian specimens. We found that N. notopterus is a complex of two allopatric species that diverge from each other by 7.5% mean p-distance. The first species is endemic to South Asia (from Indus basin to Ganga-Brahmaputra system), whereas the distribution of the second species is restricted to Southeast Asia. The exact limit between the distributions of these two species is not known, but it should fall somewhere between the Ganga-Brahmaputra and Salween basins, a region already identified as a major faunal boundary in the Oriental region. The name N. notopterus is retained for the Southeast Asian species, while the name Notopterus synurus (Bloch & Schneider, 1801) should be applied to the South Asian species. A comparative morphological study is needed to reveal the degree of morphological differentiation between the two species.
Orient, molecular taxonomy, biogeography, biodiversity, cryptic species
The complex geological history of the Oriental region caused a high degree of geographical genetic structure within freshwater organisms and species, once considered widely distributed in this region, are often formed by distinct genetic lineages (e.g.
Specimens of N. notopterus are identifiable from all other Oriental freshwater fishes based on (amongst other features) their distinct tapered tail and the corners of their mouth below eye (not behind as in the other Oriental notopterid genus Chitala Fowler, 1934) (Fig.
A Map covering the Oriental biogeographic region and showing the distribution of localities (black and red circles) of specimens of Notopterus examined in this study. Black star indicates the estimated type locality of Notopterus notopterus in Java (i.e. Jakarta region) and red stars indicate the likely origin localities of the two syntypes of Notopterus synurus (i.e. coast of Malabar and Coromandel coast at Tharangambadi [formerly Tranquebar]). Main Oriental river basins from West to East: 1. Indus basin; 2. Ganga-Brahmaputra river system; 3. Irrawaddy basin; 4. Salween basin, 5. Mekong basin. Insert shows the left lateral view of a specimen of Notopterus notopterus (Penang State, west Peninsular Malaysia; 20 cm in standard length, voucher specimen number USMFC (3) 00002, NO_1). B The unrooted network constructed with the software PopArt and a median-joining algorithm showing the COI haplotype relationships within the genus Notopterus. Branch lengths are not proportional to the number of changes. Red circles indicated haplotypes of Notopterus synurus (South Asia) and black circles indicated haplotypes of Notopterus notopterus (Southeast Asia).
We herein investigated the genetic diversity within the genus Notopterus across its full range. For that, we analysed a dataset comprising 72 publicly available sequences of the standard barcoding fragment (655 base pairs) of the cytochrome oxidase I (COI) gene that were determined from specimens of Notopterus with precise information on their geographical collection plus two COI sequences extracted from two complete mitogenomes from two specimens of Notopterus without precise localities (
Using the NCBI GenBank nucleotide database (https://www.ncbi.nlm.nih.gov/), we searched for available cytochrome oxidase subunit I sequences of N. notopterus (search made on 02/12/2019) using the terms “Notopterus” and “oxidase.” This search retrieved 88 mitochondrial entries (excluding three entries related to whole mitogenomes), from which we selected only those with either latitude-longitude coordinates or geographic localities sufficiently precise that we can confidently estimate their latitude-longitude coordinates. After this initial screening, the dataset included partial COI sequences of 77 specimens of Notopterus. We then checked the length and characteristics of these sequences using the software Mesquite version 3.31 (
To determine the COI sequences of these specimens, we used the PCR technique to amplify them using the following PCR primer pair: forward FishF1 (5´TCAACCAACCACAAAGACATTGGCAC-3´) and reverse FishR1 (5´-TAGACTTCTGGGTGGCCAAAGAATCA-3´) (
The alignment of the 78 COI nucleotide sequences was done by eye. Some sequences were shorter than others (at the 5’ and 3’ ends) and the overall proportion of missing data in the alignment was 4.6%. The alignment comprised 655 positions of which 62 were parsimony-informative. The alignment in Phylip format is provided as Suppl. material
The haplotype network is shown Fig.
The minimal genetic distance separating the genus Notopterus into two main groups is well above 3% (using COI marker) which is considered as a conservative threshold between population and species levels in vertebrates (
Our COI-based results strongly support the presence of two allopatric species of Notopterus which need names. There are several nominal species of Notopterus which have been described from Southeast Asia and South Asia and several of these names are available. To determine which name should be applied to each of our two species, we examined the synonym lists of
Notopterus notopterus was described and illustrated by Pallas in 1769 as Gymnotus notopterus from a specimen said to have been collected nearby Ambon [Ambon Island], Indian Ocean, a region where this species has never been recorded since.
Whereas the genetic evidence presented in this work supports the recognition of two valid living species of Notopterus, a detailed morphological comparison of the two species is lacking. Such morphological study is needed to identify possible diagnostic characters (in addition to the molecular diagnostic characters presented in this study) and to document the early diversification of the genus Notopterus in the Orient. In this respect, a fossil of Notopterus, morphological similar to living species, indicates that this genus was already present in Sumatra at least 33 million years ago (the Eocene-Oligocene boundary) (Sanders 1934). In addition, because of the cryptic diversity occurring in the genus Notopterus and the difficulty to identify the type localities of species of this genus, it will be important to designate a neotype for N. notopterus and a lectotype for N. synurus. Finally, the geographic coverage needs to be expanded with the study of specimens collected from the Mekong basin, Indus basin and, especially, from the region comprising the Irrawaddy basin situated between the Ganga-Brahmaputra river system and the Salween basin to determine the location of the exact distributional limit between these two species.
We conducted fieldwork in Tasek Bera (Pahang, Peninsular Malaysia) under permit reference number 100-34/1.24Jld14(67) delivered by the Department of Wildlife and National Parks (DWNP). We thank the staff of Tasek Bera Reserve and Siti Zuliana Ahmad (USM) for their assistance in the field. We express our gratitude to Richard van der Laan and Ron Fricke (Eschmeyer’s Catalog of Fishes) for helpful discussions on the nomenclature of these fishes. We also thank Nicolas Hubert (editor) for handling our manuscript and Erick Guimarães and Rupert Collins (reviewers) for their constructive comments on the submitted version of this work. This study was supported by a short-term research grant 304/PBIOLOGI/6315400 from Universiti Sains Malaysia to SL.
Table S1
Data type: Genetic data information
Explanation note: List of COI sequences of specimens of Notopterus mined from Genbank and examined in this study along with their Genbank accession numbers, the geographical origins with geographical coordinates (in Decimal Degrees) of specimens and the published references where sequences were published.
DNA Data matrice
Data type: Phylogenetic
Explanation note: Phylogenetic matrice used in the comparative part of this work.