Phylogeography and Population structure of Bigeye Tuna (Thunnus obesus) Inferred from Mitochondrial DNA sequences
Date Issued
2008
Date
2008
Author(s)
Chiang, Hsin-Chieh
Abstract
Phylogeography and population structure of bigeye tuna (Thunnus obesus), an important commercial species widely distributed throughout the Pacific Ocean, Indian Ocean and Atlantic Ocean were investigated using the first hypervariable region (HVR-1) of the mitochondrial control region sequence data. A total of 695 specimens were sampled from five regions in the Pacific Ocean (Western Pacific, Hawaii, Line, Marquesas and Eastern Pacific), five regions in the Indian Ocean (Cocos Islands, Southeastern Indian Ocean, Southwestern Indian Ocean, Seychelles and South Africa), and three regions in the Atlantic Ocean (North Guinea, South Guinea and Brazil). The reconstructed neighbor-joining phylogenetic tree showed that haplotypes from the Pacific Ocean and Indian Ocean could be grouped into two clades (Clade I and Clade III), whereas in the Atlantic Ocean, two divergent clades (Clade I and Clade II) coexisted. Each single stock of bigeye tuna in the Pacific, Indian and Atlantic Oceans was supported by hierarchical AMOVA tests and pairwise ΦST analyses. The Clade I phylogroup was a ubiquitous inter-oceanic clade which dominated the Pacific and Indian Oceans, making up 99% and 98% of these specimens. Clade II was a specific group exclusively restricted to the Atlantic Ocean which made up 72.3% of its specimens. A minor phylogroup, Clade III existed in both the Pacific and Indian Oceans with an exception in the Eastern Pacific Ocean. Significant negative Fu’s FS statistics and unimodal mismatch distributions indicated that the Clade I and Clade II phylogroups were from expanding populations. The low Harpending’s raggedness indexes further evidenced population expansion. The secondary contacts between previously differentiated allopatric lineages appeared to be a more possible explanation in this scenario.
Subjects
Bigeye tuna
population genetics
phylogeography
mitochondrial DNA
control region
Pacific Ocean
Indian Ocean
Atlantic Ocean
Type
thesis
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