Zoological Studies

Vol. 46 No. 3, 2007

Molecular Systematics of the Freshwater Prawn Genus Macrobrachium Bate, 1868 (Crustacea: Decapoda: Palaemonidae) Inferred from mtDNA Sequences, with Emphasis on East Asian Species

Min-Yun Liu1, Yi-Xiong Cai2, and Chyng-Shyan Tzeng1,*

1Department of Life Sciences, National Tsing Hua University, 101 Kang-Fu Road, Sec. 2, Hsinchu 300, Taiwan
2Biodiversity Centre, National Parks Board, 1 Cluny Road, Singapore, 259569, Republic of Singapore

Min-Yun Liu, Yi-Xiong Cai, and Chyng-Shyan Tzeng (2007) Based on the mitochondrial DNA fragment of the large subunit (16S) ribosomal RNA gene, the monophyletic phylogeny of the genus Macrobrachium, including both land-locked and euryhaline species, was supported.  There was, however, poor support for the internal structure.  Results suggest that the evolution of this group was marked by rapid radiation.  The 2 hypotheses that the prawns originated from marine ancestors and subsequently migrated towards fresh water in more than 1 wave of migration and that the abbreviated larval development of land-locked species represents adaptive convergence are both supported.  It appears that most of the morphological characters commonly used to determine the taxonomy of genus evolved independently during the invasion of inland waters.  Based on a fragment of 16S and a fragment of the cytochrome oxidase subunit I (COI) gene, several species groups, including species from different geographic regions and endemic groups were recognized from various continents (or regions).  The presence of 5 cryptic species was indicated, and the identities of 4 supposedly undescribed species are confirmed.  Localized speciation events in East Asia can be correlated with morphological similarities, notably members of the M. asperulum species group.  Morphological characters tend to be conserved within species but quite variable between geographically distant populations, making species identification difficult.  The present molecular results combined with morphological datasets can be used to help reorganize the taxonomy of various species groups.

Key words: Molecular systematics, Phylogeny, Land-locked species, Macrobrachium, Cryptic species.

*Correspondence: Tel: 886-3-5742765.  Fax: 886-3-5742765. E-mail:cstzeng@life.nthu.edu.tw