may affect the plant differentially, plant traits should evolve to maintain the relationship

with the ant partners that provide the greatest net benefit (Stanton 2003). Although

virtually all C. alliodora plants beyond the seedling stage produce domatia at branch

junctures, most of the 1-yr-old plants in this study were still small and had only a few

domatia. However, the 2-yr-old trees had a large number of domatia-significantly more

than the 5-yr-old plants-that housed young colonies of many ant species. If rapid plant

growth during the first 2 years of development results in the production of more domatia,

then the probability of mutualistic ant species, such as A. pittieri or Cr. carinata, would

increase (Tillberg 2004). The ant community composition data showed that as the plant

cohorts aged, these two ant species were also competitively superior and dominated

nearly all the trees within 5 years of establishment. If they are indeed mutualists (see

Chapter 3 of this thesis, Tillberg 2004), then their numerical dominance over other ant

species likely provides significant fitness benefits for C. alliodora. The benefits to the

host plant afforded by mutualist ant species in turn could have affected the evolution of

allocation for domatia production and perhaps other traits that benefit these ant species in

particular (Brouat and McKey 2000).

 In this study, I have described the patterns of ant occupancy in C. alliodora and

attempted to explain them through invoking the life-history characteristics of the ant

species, changes in branching structure related to the age of the host plants, the

differential abundance of honeydew-producing coccoids in different parts of the tree, the

effect of parasitoid wasps attacking one of the dominant ant species, and the interaction

of these mechanisms across space and through time. Although coexistence and

competition have been studied in ant-plant mutualisms, most research has focused on