台灣島上淡水沼蝦屬分布與其生物地理起源之關係

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

台灣15種淡水沼蝦在島上的分布範圍，可區分爲東岸型及全島型等2種分布類型。東岸型均爲兩側洄游性物種，分別爲Macrobrachium equidens、M. mammillodactylus、M. latidactylus、M. gracilirostre、M. lepidactyloides、M. lar、M. placidulum、M. jaroense、M. esculentum、M. latimanus及M. australe 等11種，牠們分布在台灣的東部，部分物種亦分布在鄰接的北部及南部地區，其中M. australe則另分布在台灣的西北部。這些物種皆來自東南亞島嶼，並經由菲律賓來到台灣，其在島上的分布及擴散來台的途徑與黑潮關係密切。全島型包括4 種，分別爲M. japonicum、M. formosense、M. asperulum 及M. nipponense，前者在台灣種化形成，後3種則源自於中國大陸。牠們廣泛分布於台灣的溪流，其中M. japonicum 及M. formosense爲兩側洄游性，其在島上的分布型態與兼具兩側洄游的M. nipponense及陸封性的M. asperulum極爲相似，卻與同爲兩側洄游性的東岸型物種之分布極爲不同，顯示M. japonicum 及M. formosense或許並非全然爲兩側洄游性，而是如M. nipponense爲兼具兩側洄游性的物種，此點需要進一步的研究證實。台灣淡水沼蝦在島上的分布型態，是演化過程中物種地理起源、擴散來台途徑及其對環境適應能力等因素所造成。

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.