Pruning behavior and intercolony competition of Tetraponera (Pachysima) aethiops (Pseudomyrmecinae, Hymenoptera) in Barteria fistulosa in a tropical forest, Democratic Republic of Congo

The early stages of colonization by Tetraponera (= Pachysima) aethiops (Pseudomyrmecinae) to its obligate host plant, Barteria fistulosa (Passifloraceae), was studied in Kahuzi-Biega National Park, Democratic Republic of Congo (formerly Zaire). In our observations, as many as 36 queens colonized a seedling, and all of the established colonies had just a single queen each. The ants depend totally on the products of scale insects which inhabit the domatia. The ants damage the terminal meristems of the branches where other incipient colonies may inhabit. This tip-biting behavior may deteriorate the nutritional condition of scale insects and suppress the growth of the competing colonies. Ants pruned the plants near the edge of the trunk of the host tree most intensively, even the foliage of the lowest branch in shade. This observation supports the hypothesis that the main driving force which leads to pruning behavior is intercolony competition rather than improving the light condition of the host tree.