Comparative phylogeography of widespread and endemic damselfishes in the Hawaiian Archipelago

The Hawaiian Archipelago, one of the most remote archipelagoes in the world, is a hotspot for reef fish endemism. The restricted biogeographic range sizes of endemic species have been interpreted to indicate low dispersal ability, whereas broad distributions of widespread species are assumed to indicate high dispersal potential. To assess that intuitive link, we analyzed mitochondrial cytochrome b and control region sequence data for two widespread damselfish species (Abudefduf vaigiensis and Chromis vanderbilti) across the Hawaiian Archipelago and broader Indo-Pacific and compared with three Hawaiian endemic damselfishes (A. abdominalis, C. ovalis, and C. verater). The widespread species exhibited less population structure in the Hawaiian Archipelago than the endemics. Across the larger spatial scale of their Indo-Pacific ranges, both widespread damselfish species showed strong and significant population structure. Our comparison of widespread and endemic damselfish species is consistent with the expected trend for widespread species to exhibit more connectivity within the Hawaiian Archipelago, but this pattern may be restricted to certain reef fish families. In addition, widespread species in this study and previous studies, which had little to no population subdivision within archipelagoes, have shown strong genetic structure when analyzed across the broader Indo-Pacific. We conclude that geographic range size may be a better indicator of dispersal ability at smaller (within archipelago) rather than at larger spatial scales (across oceans). Management should note that reef fishes unique to Hawaii seem to have less gene flow across the archipelago than more broadly distributed Indo-Pacific species.