Hawaiian biogeography and the islands' freshwater fish fauna

Aim This paper describes known patterns in the distributions and relationships of Hawaiian freshwater fishes, and compares these patterns with those exhibited by Hawaii's terrestrial biota. Location The study is based in Hawaii, and seeks patterns across the tropical and subtropical Indo‐west Pacific. Methods The study is based primarily on literature analysis. Results The Hawaiian freshwater fish fauna comprises five species of goby in five different genera (Gobiidae). Four species are Hawaiian endemics, the fifth shared with islands in the western tropical Pacific Ocean. All genera are represented widely across the Indo‐west Pacific. All five species are present on all of the major Hawaiian islands. All five species are amphidromous – their larval and early juvenile life being spent in the sea. Although there has been some local phyletic evolution to produce Hawaiian endemics, there has been no local radiation to produce single‐island endemics across the archipelago. Nor is there evidence for genetic structuring among populations in the various islands. Main conclusions In this regard, the freshwater fish fauna of Hawaii differs from the well‐known patterns of local evolution and radiation in Hawaiian Island terrestrial taxa. Amphidromy probably explains the biogeographical idiosyncrasies of the fish fauna – dispersal through the sea initially brought the fish species to Hawaii, and gene flow among populations, across the archipelago, has hitherto inhibited the evolution of local island endemics, apparently even retarding genetic structuring on individual islands.