Print PageEcological theory suggests that interspecific tradeoffs among life-history traits, notably dispersal and competitive ability, can help maintain diversity in species rich communities. In tropical ecosystems, species from over 40 genera of ants establish colonies in the stems, hollow thorns, leaf pouches, or petioles of specialized plants. Because multiple ant species often vie for the same species of host-plant, competition-colonization tradeoffs are thought to be an important mechanism promoting the coexistence of competing ant species. However, virtually nothing is known about the relative dispersal ability of foundress queens competing for access to the same host plants. We used empirical data and inverse modeling – a technique developed by plant ecologists to model seed dispersal – to quantify and compare the dispersal kernels of queens from three Amazonian ant species that compete for access to host-plants. The three ant species include the competitively inferior species Crematogaster laevis and the competitive dominants Pheidole minutula and an undescribed species of Azteca. These species compete for access to the host plants Tococa bullifera and Maieta guianensis (both Melastomataceae).
Results/Conclusions
We found that the modal dispersal distance of queens from the three species varied 8-fold, with the poorer competitor (C. laevis) having the greatest modal dispersal distance (40 m). However, our results also suggest that queens of Azteca sp. have maximal dispersal distances that are four-sixteen times greater than those other species. Our results are consistent with the hypothesis that there are tradeoffs between competitive ability and dispersal capacity in tropical plant-ants. They also suggest that for some ant species, limited dispersal capability could pose a significant barrier to the rescue of populations in isolated forest fragments. These results have important implications for the demography of the two species of host-plants. Finally, we demonstrate that inverse models parameterized with field data are an excellent means of quantifying the dispersal of ant queens.
