The ants of remote Polynesia revisited

The islands of remote Polynesia (east of Rotuma, Samoa, Tonga and New Zealand) have long been thought to contain few, if any, native ants. The findings of recent sediment core studies, however, challenge this conventional wisdom and indicate some species may be native. The majority of ant species in remote Polynesia, however, are introductions from tropical and subtropical regions around the world. Despite this diversity of origins, and the lack of a common coevolutionary history in the region, patterns of organization in remote Polynesian ant communities are generally similar to those observed in coevolved continental areas. The distribution of ant species across Polynesia is consistent with a primary mechanism of anthropogenic introductions, with the availability of suitable habitat as a secondary mechanism. The species-area relationship for better-collected Polynesian islands reveals these islands are depauperate compared to Melanesian islands with endemic species. Four out of five of the “world’s worst” invasive ant species are present in remote Polynesia. Recent studies have documented how range expansions of such ant species have had detrimental effects on native arthropod populations, although the overall effects of introduced ants per se on naïve endemic island arthropods may never be known with certainty. Considering the relatively fragile nature of island ecosystems, and the potential transformative effects of invasive ants on arthropod communities, vigilance is required to prevent the spread of invasive ant species across Polynesia.