Population Genetics, Phylogeography And Dna Barcoding Of The Japanese SCAD, Decapterus maruadsi (Temminck & Schlegel, 1843) In Sundaland And Neighbouring Waters
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Date
2017-07
Authors
Jamaludin, Noorul Azliana
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Decapterus maruadsi or Japanese scad is one of the economically important to Southeast Asian people. Belong to the scad’s group for Carangidae family, the total landing of scad for the past 11 years has been maintained in South China Sea between 600 to 700 metric tan (mt) while decreasing during last five years in Andaman Sea accept Thailand (Abu Talib et al., 2013). Furthermore, it was reported that scad or Decapterus spp. was concluded to be overexploited based on exploitation rate (E) that was 0.71 based on the survey conducted by SEAFDEC/MFRDMD from 2002 to 2006. Therefore, it is an alarming to fishery managers to know what is the current stock of this species today for sustainable fishery management in Southeast Asia region. A population genetics and phylogeographic study of the Japanese scad, Decapterus maruadsi in the marine waters of Sundaland and neighbouring waters of Vietnam (Nge Anh, Ca Ba- northern Vietnam, Khanh Hoa- central Vietnam) and Philippines (Rosario) were conducted based on mitochondrial Cytochrome b gene (Cyt b) method. The analysis of Cyt b on 12 populations and 320 specimens revealed low nucleotide diversity π (0.0002 – 0.03) and low-to-high haplotype diversity h (0.185 – 0.960) were observed. However, with the exclusion of the Bagan Panchor, Rosario, Ranong and Khanh Hoa populations which showed atypical results, the genetic diversity were; π (0.001 – 0.003 and h (0.503 – 0.822) which translated to low nucleotide diversity and moderate to high haplotype diversity. Relative genetic homogeneity within the Sundaland–Rosario-Ranong group was observed. However, obvious genetic structure was observed between Sundaland–Rosario-Ranong and the northern Vietnam clusters as revealed by FST, AMOVA and SAMOVA, while the central Vietnam population of Khanh Hoa formed an admixed group of the two differentiated regions. The neutrality and mismatch distribution analyses supported a demographic history of D. maruadsi expansion in the late Pleistocene which has influenced present day distribution pattern. However, contemporary factors such as oceanic currents and larval behaviour are also believed to play a significant role in the observed population structure and geographic pattern. The Bagan Panchor, Rosario and Ranong populations showed very low levels of genetic diversity which could be attributed to historical events as well as overharvesting of this commercially important species. A DNA barcoding study based on the mitochondrial cytochrome c oxidase subunit I (COI) gene was also conducted in the second part of the project. The COI gene, although not focusing on population and phylogeographic analyses was also in agreement with findings from the Cyt b gene. The COI DNA barcoding gene also highlighted the likely presence of a cryptic or a new species discovery. However, further studies on a larger and increased number of populations as well a more holistic approach including re-examination of morphology will be required to confirm this potentially new taxonomic discovery. As a conclusion, the molecular information obtained from this study could be utilized for strategizing management activities of the D. maruadsi stocks in Southeast Asia.
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Keywords
Decapterus maruadsi or Japanese scad is one of , the economically important to Southeast Asian people