Molecular Systematics, Historical Biogeography And Population Genetics Of The Asian Spiny Eel (Synbranchiformes: Mastacembelidae)

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Date
2017-08
Authors
Jamaluddin, Jamsari Amirul Firdaus
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Publisher
Universiti Sains Malaysia
Abstract
The dynamic geological and climatic history of Southeast Asia is hypothesized as the most important aspects driving present day species richness, diversification and distribution of biodiversity across the region. A plethora of studies undertaken to test this theory, however, offers varied and conflicting results. Towards a better understanding of these effects, the current study utilised a combination of nuclear and mitochondrial DNA markers to address the Asian mastacembelids systematics (Chapter 3) and population genetic structure (Chapter 5), subsequently evaluate the role of vicariance and dispersal events on its evolutionary diversification and current distribution. First, the molecular phylogenetic relationships in Asian mastacembelids was investigated using 102 individuals from 17 putative species based on mitochondrial (cytochrome b and cytochrome oxidase c subunit 1) and nuclear (first intron of the nuclear S7 ribosomal protein) DNA sequences. Phylogenetic analyses concur with previous morphologically defined species classification except for the Mastacembelus armatus species group. There is also compelling evidence for new species discovery in one of the two Macrognathus circumcinctus clades, Macrognathus cf. maculatus and Macrognathus aff. tapirus. The current data hypothesised that the transcontinental distribution of the mastacembelids arose as the consequence of a dispersal event from Asia to Africa in the early Miocene. Early diversification of Asian mastacembelids is suggested to have taken place in late Oligocene, with Miocene identified as a time of significant species radiation, linked to the large-scale changes in drainage patterns associated with the intensive tectonic uplifts in eastern Tibet and sea level oscillations in Sundaland. The dominant role of west to east dispersal and vicariance was also apparent. The following section of this study documented the phylogeographical history and population structure of the tire track eel (Mastacembelus favus) based on 570 individuals across most of its natural distribution using eight newly developed microsatellite loci and cytochrome b sequence data. Phylogenetic analyses classified all haplotypes into two evolutionarily significant units that have evolved separately approximately 5.4 million years ago. Admixture analysis provided some evidence of interbreeding, indicating that even after long period of allopatry, divergence had not resulted in complete reproductive isolation. One lineage is confined to the upper reaches of the lower Mekong to middle Mekong, while the other appeared to have a widespread distribution across mainland Southeast Asia and eastern part of Peninsular Malaysia. Phylogeographic signal also indicated that Pliocene local tectonic events and Pleistocene sea level oscillations which are attributed to intensive climatic fluctuations may have played a pivotal role on the evolution and demographic history of the species. Taking Mastacembelidae as an example, even in well-studied river systems, the tropical fish diversity is still underestimated and far from resolved as illustrated in the current study. The results of this study provided critical information in resolving mastacembelids taxonomic uncertainties and understanding the geomorphological history of Southeast Asia.
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Keywords
Molecular systematics, historical biogeography , and population genetics
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