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Disequilibrial island turnover dynamics: a 17-year record of Bahamian ants


Correspondence: Lloyd W. Morrison, Department of Biology, Missouri State University, 901 S. National Avenue, Springfield, MO 65897, USA.


Aim  To document long-term rates of immigration, extinction and turnover in insular ant faunas and evaluate the relative impacts of recent hurricane activity and climate change.

Location  Small islands in the Exuma Cays, Andros and Abaco archipelagos of the Bahamas.

Methods  I surveyed the ant faunas of > 140 small islands in three archipelagos of the Bahamas over several multi-year periods, spanning up to 17 years, by recording species attracted to baits. Immigrations, extinctions and species turnover were documented, as were the relative abundances of species. Four major hurricanes affected the study archipelagos in the second decade of this study.

Results  Rates of ant turnover were generally low among archipelagos and time periods. Immigrations outnumbered extinctions in the first decade of this study, although this pattern was reversed in the second decade. General physical characteristics of the islands were not significant predictors of the occurrence of extinctions. The relative abundance (based on proportion of baits occupied) of persistent populations of the two most common species both declined in the second decade, indicating, along with higher extinction rates, a generalized decline in these insular ant faunas.

Main conclusions  The available evidence suggests that hurricanes were not directly responsible for the observed declines in the ant faunas. Regional changes in insular ant species richness, however, are correlated with generalized North Atlantic hurricane activity over the last half century. Indirect effects of hurricanes on the vegetation of these islands, such as increased herbivory and possible decreased nutrient availability, along with a long-term (quarter century) increase in temperature and decline in rainfall, are possible contributing factors to the changing ant turnover dynamics.