Abstract
Members of the freshwater halfbeak genus Dermogenys are hard to identify to the species level, despite several previous attempts to isolate fixed meristic, morphometric and colour pattern differences. This has led to ongoing confusion in scientific literature, records of species occurrence, and entries in museum collections. Here, a DNA barcoding study was conducted on the genus to gain further understanding of its taxonomic status across the Southeast Asian region. Fish were collected from 33 localities, spanning freshwater and brackish habitats in Malaysia, Western Indonesia, Thailand and Vietnam. In total, 290 samples of Dermogenys spp. were amplified for a 651 base pair fragment of the mitochondrial cytochrome oxidase c subunit I (COI) gene. Analysis was able to successfully differentiate the three species: D. collettei, D. siamensis, D. sumatrana; reveal the presence of a new putative species, Dermogenys sp., that was sampled in sympatry with D. collettei at three locations; as well as uncovering two genetic lineages of a fifth species, D. bispina, that display non-overlapping geographical distributions in drainages of northern Borneo; Kudat and Sandakan. This study expands the barcode library for Zenarchopteridae, demonstrates the efficacy of DNA barcoding techniques for differentiating Dermogenys species, and the potential thereof in species discovery.
Highlights
Members of the freshwater halfbeak genus Dermogenys are hard to identify to the species level, despite several previous attempts to isolate fixed meristic, morphometric and colour pattern differences
Analysis was able to successfully differentiate the three species: D. collettei, D. siamensis, D. sumatrana; reveal the presence of a new putative species, Dermogenys sp., that was sampled in sympatry with D. collettei at three locations; as well as uncovering two genetic lineages of a fifth species, D. bispina, that display non-overlapping geographical distributions in drainages of northern Borneo; Kudat and Sandakan
Most of the individuals collected (70%) were adults and could be putatively assigned to their morphological species using the techniques outlined in the Methods section. This resulted in the identification of five morpho-species: D. collettei Meisner[11] (30%), D. sumatrana Bleeker[55] (14.8%), D. siamensis Fowler[56] (17.6%), D. bispina Meisner & Collette[1] (3.1%), and a newly observed group referred to as Dermogenys sp. (4.8%)
Summary
Members of the freshwater halfbeak genus Dermogenys are hard to identify to the species level, despite several previous attempts to isolate fixed meristic, morphometric and colour pattern differences. The genus is viviparous (bearing live young) and generally limited to freshwater and estuarine habitats, suggesting low dispersal capacity; yet has a wide natural geographical distribution, including large mainland rivers such as the Mekong and drainages of the Indonesian and Philippine archipelagos These factors mean the genus presents a tractable model for investigation of factors affecting phylogeographical pattern[12] in what is a biogeographically complex and biologically diverse region of the tropics[15,16]. Meisner & Collette[1] named a new Dermogenys species from Sabah as D. bispina This was followed by the discovery of a further four species, differentiated based on phylogenetic analysis of the gonadal histology and embryonic modifications associated with viviparity, and on osteological characters in modified anal fin rays[11]. There are 12 morphologically recognised species of Dermogenys in the Southeast Asian inland waters, as reviewed by Meisner[11]
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