Distribution of the Freshwater Prawns (Macrobrachium Bate, 1868) in Taiwan in Relation to Their Biogeographic Origins

Abstract

Using data collected from the freshwater prawn inventory survey of 2000-2008 and historical data obtained from literature prior to 2000, distribution patterns of 15 species of the Macrobrachium prawns in Taiwan were examined. They were able to divide into two groups: the east-coast group and the islandwide group. The east-coast group contained 11 amphidromous species: M. equidens, M. mammillodactylus, M. latidactylus, M. gracilirostre, M. lepidactyloides, M. lar, M. placidulum, M. jaroense, M. esculentum, M. latimanus and M. australe. They were found in the east coast, some of them in its adjacent northern and southern regions. They were the Southeast Asia origins and dispersed to Taiwan mainly through the Philippines, and showed close association with the Kuroshio Current in the dispersion. The island-wide group contained 4 species: M. japonicum, M. formosense, M. asperulum and M. nipponense. The former species was postulated to have evolved within the island of Taiwan, while the latter three species were originated from the China mainland. They were common in streams around the island. M. japonicum and M. formosense that have been considered to be amphidromous showed the distribution patterns fairly similar to that of non-obligatory amphidromous M. nipponense and even to that of landlocked M. asperulum, rather than to those of the amphidromous species of the east-coast group. The evidences suggest that these two species might not be the amphidromous but the non-obligatory amphidromous, but a further study is needed for the confirmation. The distribution patterns of the Macrobrachium prawns in Taiwan are resulted from their life cycle modes, adaptability to local environments at present and biogeographic origins and dispersal routes in the past evolutionary history.