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
Journal Title
Journal ISSN
Volume Title
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.
Description
Keywords
Molecular systematics, historical biogeography , and population genetics