Relationship between Plant Size and Ant Associates in Two Amazonian Ant‐Plants1

Abstract

ABSTRACTA survey of two Amazonian melastome ant‐plants,Maieta guianensisandTococa bullifera, revealed a significant difference in plant size according to the species of ant inhabiting the plant. Plants withCrematogaster laevis, on average, were smaller than those withPheidole minutula(inM. guianensis)and those withAztecasp. (inT. bullifera).There is no evidence that these patterns were due either to the deterministic replacement ofC. laevisby another ant species during host‐plant ontogeny or to a habitat effect on plant growth rates coupled with colony survival. More likely, the smaller size ofC. laevisplants can be explained by its effects on host‐plant performance. Plants withC. laevislost their associated ant colonies more frequently than plants withP. minutulaandAztecasp. Plants that lost theirC. laeviseither died, or more commonly, were severely defoliated. Defoliated plants, once sprouted, tended to become recolonized, but such recolonizations were not deterministic so as to favor one species over another. Plants withC. laevisshowed similar, or only slightly greater, standing levels of herbivory than plants withP. minutulaorAztecasp. This suggests that whenC. laevisis present, it confers some degree of protection to its hosts. It was found that early in colony development, queens ofC. laevismoved off their host plants to build satellite nests in dead twigs on the ground, a behavior not seen in the other two species and one that possibly renders colonies more vulnerable to mortality from predation, flooding, or nest decay. Comparable 815N values inC. laevisandP. minutulaindicate that the two species are equally dependent on food supplied by the host plant.