Zoological Studies

Vol. 48 No. 6, 2009

Speciation and Population Structure of Three Trichiurus Species Based on Mitochondrial DNA

Kui-Ching Hsu1, Nien-Tsu Shih2, I-Hsun Ni2, and Kwang-Tsao Shao1,*

1Biodiversity Research Center, Academia Sinica, Nankang, Taipei 115, Taiwan
2Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, Keelung 202, Taiwan

Kui-Ching Hsu, Nien-Tsu Shih, I-Hsun Ni, and Kwang-Tsao Shao (2009) This study integrated most available genetic data of the “Trichiurus lepturus complex” and examined its species status and population structure using mitochondrial (mt) DNA sequences.  Both the maximum-parsimony and Neighborjoining distance trees supported 3 clear branches at 100% bootstrap value support.  Due to a decisive genetic difference based on mtDNA cytochrome b, cytochrome oxidase subunit I, and 16S ribosomal RNA with the Kimura 2 parameter or maximum composite likelihood models, all historically confusing “T. lepturus complex” morphs were suggested to be 3 separate species: T. japonicus, T. lepturus, and T. sp. 2.  This study suggested that T. lepturus from the Indo-Pacific in previous studies and T. sp. 2 are the same species.  During the Miocene, these 3 Trichiurus species diverged from each other.  According to the mtDNA phylogeographical patterns presented here, the vicariance events important to the speciation or structure of the “T. lepturus complex” were: (1) a warming event occurring around Japan during the middle Miocene, (2) cold water upwelling close to the tip of South Africa, (3) archipelagoes of the West Pacific, (4) the southeastern coast of Taiwan, (5) cyclical glacial periods, (6) the Isthmus of Panama, (7) the 2500 km long stretch of deep water separating the eastern and western Atlantic, and (8) freshwater plumes of the Amazon River.  Based on current data, the East Indies Triangle of Indo-West Pacific was either a refuge or a colonization source for T. sp. 2.

Key words: Trichiurus lepturus, Trichiurus japonicus, Trichiurus sp. 2, Speciation, Phylogeography.

*Correspondence: Fax: 886-2-27883463.  E-mail:zoskt@gate.sinica.edu.tw