Ant colonization of Maieta guianensis seedlings, an Amazon ant-plant.

The ants Pheidole minutula and Crematogaster sp. are obligate inhabitants of the ant-plant Maieta guianensis. They nest and reproduce exclusively in this and a few other Amazon melastome ant-plants. Experimental transplants of uncolonized M. guianensis seedlings to sites at different distances from established colonies of these two ant species, which are sources of founding queens, have shown that distance is an important factor affecting seedling colonization by ants. The proportion of colonized seedlings and the average number of colonizations per seedling, both by Crematogaster sp. and P. minutula, decreased as distance from established colonies increased. Seedling colonization was also affected by rainfall and fewer seedlings were colonized during the dry season, especially by P. minutula, than during the rainy season. P. minutula queens usually cooperate with each other during colony foundation, a behaviour not observed among founding queens of Crematogaster sp. Competition between these two ant species for host-plants appears to be strong as 63.6% of the seedlings colonized by Crematogaster sp. were also colonized by P. minutula during a 15-month observational period. However, there was generally an interval of a few months between colonizations, possibly giving the first species to colonize the plant a better chance of domination on this plant.