(44) Ant Acacias that Resprout in Rainforest Gaps Following Hurricanes Host Higher Numbers of Ant Mutualists

     Tropical tree regeneration associated with light gaps is characterized by intense competition and increased rates of herbivory. Tree species defended by ant mutualists may have an adaptive advantage in these... [ view full abstract ]

     Tropical tree regeneration associated with light gaps is characterized by intense competition and increased rates of herbivory. Tree species defended by ant mutualists may have an adaptive advantage in these environments. One such rainforest mutualism, the ant-acacia mutualism, occurs between the bullhorn acacia (Vachellia cornigera) and the acacia ant (Pseudomyrmex ferruginea), where the bullhorn acacia hosts the ants in swollen, hollow thorns, and the ants, in return, confer defense against herbivory and plant competition. In recent light gaps created by Hurricane Earl within the Chiquibul Rainforest of Belize, we observed that bullhorn acacia trees hosted higher densities of swollen thorns compared to in non-gap conditions. We hypothesized that a greater thorn density in bullhorn acacias regenerating in gaps allowed for a higher density of defending ants per stem. Ants were extracted from swollen thorns harvested from 20 bullhorn acacia sprouts in paired gap and non-gap conditions. We found that the number of ants were positively correlated with the number of swollen thorns, and that there was a greater number of thorns and ants on individuals in the gaps. The ability of the bullhorn acacia trees to resprout with greater numbers of swollen thorns allows individual stems to host an increased ant defense system.  We believe this may contribute to an increase in the abundance of ant-acacia trees relative to other rainforest species following hurricane disturbance.