Genetic Diversity And Phylogeography Of The Freshwater Halfbeak, Genus Hemirhamphodon (Teleostei: Hemiramphidae: Zenarchopterinea) In Sundaland River Basins
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Date
2017-08
Authors
Lim, Hong Chiun
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Publisher
Universiti Sains Malaysia
Abstract
The freshwater fish genus Hemirhamphodon commonly known as halfbeak consists of a total nine morphological species. Its wide distribution and endemism within Sundaland makes it suitable for phylogenetic, population and phylogeographic studies, and even the potential discovery of new species. DNA barcoding of the cytochrome oxidase subunit I (COI) gene was utilized to elucidate the systematics of the freshwater halfbeak genus Hemirhamphodon which involved 201 individuals from 46 locations in Peninsular Malaysia, northwest Borneo (Sarawak) and Sumatra. Pairwise within species comparisons exhibited a high range of intraspecific diversity from 0.0% to 14.8%, suggesting potential occurrence(s) of novel or cryptic species. This finding was further supported by the barcode gap analysis, ABGD (Automatic Barcode Gap Discovery) and the constructed COI gene tree. Population level assessment and phylogeography of H. pogonognathus, H. byssus and H. kuekenthali were also conducted with a combination of both mtDNA (cyt b region) and nDNA markers (Single Copy Nucleotide Polymorphism (SCNP) markers, Hp5 and Hp54) to assess the genetic variabilities, population structuring, historical demography as well as attempt to discover hidden diversity. Twenty five, five and eleven populations were analysed in the assessments of the H. pogonognathus, H. byssus and H. kuekenthali, respectively. The results revealed high population structure for all three species indicating that most (if not all) populations contribute to the total gene pool. In addition,
the findings highlighted the presence of hidden diversity or cryptic species which is in agreement with the initial hypothesis of new species discovery. Furthermore, the historical demographic analyses revealed that most of the populations of the three Hemirhamphodon species had experienced rapid population size reduction. Therefore, each of the Hemirhamphodon populations should be treated as a separate management unit in the context of conservation. This project also revealed that the Paleo-drainage systems of Sundaland seemed to have limited influence in driving Hemirhamphodon species diversity. On the other hand, the geological history such as the cyclical glaciation events during the Pleistocene epoch coupled with the Paleo-drainage rearrangements have greatly influenced the genetic diversity of the three Hemirhamphodon species populations. Overall, a more integrated investigation framework needs to be carried out to resolve the species complex issue, and conservation strategies and management plans should be implemented on each of the Hemirhamphodon populations for long term population sustainability and conservation of species.
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Keywords
The freshwater fish genus Hemirhamphodon , commonly known as halfbeak