Endemism in birds of tropical Pacific islands

Abstract

I analysed avifaunal data from 30 archipelagos and isolated islands in the tropical Pacific Ocean to examine the effects of geography on endemism. I divided the total bird species list (pelagic and migrant species excluded) for each island group into continental (also found outside of the study area), Pacific (found only within the study area but within more than one archipelago), and endemic (found only within a single archipelago) species and estimated ten variables related to the geography of each archipelago. I used multiple linear regression analysis to relate numbers and proportions of species in each category to the geographical variables. Total land area of an archipelago was the most improtant variable in explaining variation in the number of species in each category, with elevation and isolation also being important. The relationships between the proportions of species in each category and the geographical variables underscore the importance of isolation and the number of large islands in promoting endemism, presumably by allowing both inter- and intra-archipelagal speciation to proceed.