PHYLOGEOGRAPHY AND EVOLUTIONARY HISTORY OF FLATHEAD MULLET MUGIL CEPHALUS IN THE NORTHWEST PACIFIC DERIVED FROM MITOCHONDRIAL DNA CONTROL REGION
Date Issued
2010
Date
2010
Author(s)
Wade Delizo Jamandre, Brian
Abstract
The flathead mullet Mugil cephalus is a coastal bound and circumglobally distributed fish, and the fishery is one of the most important commercial fisheries in many parts of the world. Its life history and population dynamics have been intensively studied but its genetic structure and phylogeography remained unresolved. This study investigated the phylogeographic structure, genetic diversity, and evolutionary history of M. cephalus in the Northwest Pacific region based on the analysis of the mitochondrial control region (mtDNA CR) sequences.
Phylogenetic analysis of the CR sequences indicated that M. cephalus in the Northwest Pacific was composed of two highly divergent lineages: Lineage 1 from the East China Sea and Lineage 2 from the South China Sea. The specimens of the former were collected from Taiwan and Qingdao of North China, while those of the latter from the Philippines, Pearl River of South China, and Japan. The specimens from Okinawa and Yokosuka of Japan were a mixing between lineages 1 and 2. Historical demographic variables of both lineages indicated that Pleistocene glaciations might have strong impacts on the distribution and division of the population of M. cephalus in the northwest Pacific, resulting in a recent demographic decline for the East China Sea population but in demographic equilibrium for the South China Sea population. The results of the Phylogeographic analysis also indicated that such impacts were more drastic at high latitudes than at low latitudes, suggesting that Lineage 1 and Lineage 2 were isolated during the Pleistocene era.
The mtDNA CR sequence variations between two M. cephalus lineages largely exceeded intraspecific polymorphisms that are generally observed in other vertebrates. Therefore, the structure and sequence variations of the CR gene between M. cephalus lineages from northwest Pacific were further analyzed by comparing them with those from African, other Pacific, and Atlantic regions to assess their usefulness for the phylogeographic study. In order to prove the high mutation rate or divergence rate found in M. cephalus is not due to the mutational bias of the CR gene, mitochondrial cytochrome b (mtDNA cyt b) of a few northwest Pacific mullets were also sequenced and analyzed to determine their evolutionary rate and compared to that of the CR gene. The length of CR sequence varied among M. cephalus populations due to the presence of indels and variable number of tandem repeats at the 3’ hypervariable domain. The high evolutionary rate of the CR gene was probably originated from these mutations. The CR showed higher sequence variation as compared with the cyt b. However, there was no clear indication of the saturation on the nucleotide substitutions in these two mitochondrial genes. The high CR divergence among worldwide populaions of M. cephalus inferred from the phylogenetic tree indicated the occurrence of a rapid radiation in its evolutionary history, a peculiar case for an estuarine species with global distribution.
The results of this study showed that the high divergence of M. cephalus lineages might be due to its rapid radiation of the species in evolution and to the geographic isolation caused by geological events. Therefore, in congruence to the growing number of evidences, results obtained from this study, and its worldwide scale distribution, M. cephalus is recognizable as a complex species.
Subjects
Phylogeography
Mugil cephalus
mitochondrial DNA control region
genetic divergence
Pleistocene period
Northwest Pacific
SDGs
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-F94b45027-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):257381b8032e3a5ffd6b7dadb45d0f5b