Island biogeography and metapopulation dynamics of Bahamian ants

Aim I examined the island biogeography and metapopulation dynamics of ants inhabiting two archipelagos of small Bahamian islands. Of particular interest were measurement and comparison of turnover rates, examination of variation in relative population abundances, and the effect of a hurricane force disturbance on the ant fauna of these small islands. Location Archipelagos of small islands in the central Exumas and near the northeast coast of Andros, Bahamas. Methods Ants occupying small islands were surveyed using tuna and honey baits. I surveyed ninety-three islands in the Exumas in 1998 and fifty-eight islands at Andros in 1999, to compare with earlier surveys in both regions. The proportions of baits occupied were used as a measure of relative population abundance. A subset of seventeen small islands in the Exumas was surveyed in 1999 in the aftermath of Hurricane Floyd. Results Mean annual relative turnover rates were low: <2.5% year on a per island basis, and <7% year on a per species basis. Rates of immigration and extinction were similar, although immigrations exceeded extinctions in some comparisons. Relative population abundances of the two most common ant species varied inversely with each other. One species revealed a strong positive correlation with recent rainfall, whereas another varied strongly inversely. No extinctions of ants occurred on the seventeen small islands surveyed after Hurricane Floyd. Main conclusions Ants were found to be ubiquitous in this system, occurring on almost all vegetated islands. Ant populations were persistent over the period of study, and species rarely became extinct or colonized islands. The few instances of turnover observed appeared to occur randomly with respect to physical island characteristics. The correlational data suggest an interaction of interspecific competition and precipitation affect relative population abundances. Ants were found to be resistant to hurricane-force disturbances. In the short term (one decade), the ant fauna of these islands appears to be in a state of static equilibrium, although non-equilibrial dynamics may better characterize the system over longer time periods (several decades).