Mammalian biogeography of the Alexander Archipelago of Alaska: a north temperate nested fauna

Aim A large number of studies have analysed the distribution of mammals wit hin archipelagos, yet few have focused on islands that were heavily glaciat ed and subsequently colonized following deglaciation. Location We explored the relative effects of island area and isolation on f aunal composition based on twenty-three mammalian taxa of twenty-four islan ds of the Alexander Archipelago, Southeast Alaska. Methods We used regression of log-transformed variables and several indices of nestedness. Results These faunas showed significant nested structure using tests of nes tedness and regression models. Unlike most landbridge and mainland archipel agos studied previously, isolation appears to be the primary factor determi ning patterns of species richness. Main conclusions Colonization ability of particular taxa, rather than extin ction, has determined this nested structure. We suggest that other higher l atitude archipelagos may show similar historical patterns.