Growth and survival of incipient ant colonies in two Amazonian ant-plants: Effects of habitat, host-plant, and mode of colony founding (Hymenoptera: Formicidae)

Abstract

We assessed the effects of habitat type, host-plant species, and mode of colony founding on the survivorship and growth of incipient colonies of ants (Hymenoptera: Formicidae) associated with two Amazonian ant-plants. We experimentally colonized seedlings of Maieta guianensis with founding queens of Crematogaster laevis or Pheidole minutula, and of Tococa bullifera with Azteca sp., C. laevis, or P. minutula queens. Seedlings were then transplanted to two habitats: stream edges or forest interior, where they remained for 75 days. To prevent subsequent, natural ant colonizations we caged plants with a fine mesh. Overall, levels of mortality were greater for small bodied queens of P. minutula (50-75%), than for larger bodied queens of C. laevis (38.7-53.6%) and Azteca sp. (12.5-25.0%). While seedlings grew faster along stream edges, in general, habitat type did not significantly affect colony survival and growth. The exception to this trend was observed for colonies of P. minutula, which survived better in seedlings located on stream edges. We found a trend of greater survival of C. laevis in T. bullifera than in M. guianensis, but no effect on colony growth. In contrast, the performance of P. minutula in T. bullifera was very poor, probably because T. bullifera is not a usual host of P. minutula. Mode of colony founding did not affect survival of P. minutula colonies in M. guianensis. However, pleometrotic colonies (with 5 queens) grew significantly faster than single queen colonies, and at a rate comparable to colonies of C. laevis. This suggests that pleometrosis can be a beneficial strategy, at least when levels of intra- and inter-specific competition among incipient colonies is high.