3a), with the proportion of occupied domatia differing according to tree age and species

(Table 2-2). When it was the dominant species, A. pittieri occupied a significantly higher

proportion of the host plants' domatia than when Cr. carinata was the dominant species.

The proportion of domatia occupied by Ce. setulifer was dependent upon whether A.

pittieri or Cr. carinata was the dominant ant species in the tree (Fig. 2-3b). Specifically,

trees dominated by Cr. carinata had more domatia occupied by Ce. setulifer regardless of

tree age, and the changes in proportional occupancy of Ce. setulifer differed among trees

dominated by the two species as the plants aged. The significant "Plant age x Ant

species" interaction term suggests that A. pittieri increasingly excluded Ce. setulifer as

the plants aged, whereas Ce. setulifer occupied an increasing proportion of domatia on

trees dominated by rC. carinata as the plants aged (Table 2-3).

Colony Founding and Expansion

 Most ant species inhabiting C. alliodora were present on 1-yr-old trees only as

founding queens or very small colonies. The 2-yr-old trees were always occupied by

multiple con- and heterospecific colonies, most of them with small numbers of workers.

In these trees, domatia were colonized both through expansion of growing colonies and

by establishment of new colonies by foundress queens in unoccupied domatia (Tillberg

2003). When the plants were 5 years old and fewer unoccupied domatia were available,

the occupation of newly produced domatia appeared to occur primarily by colony

expansion. However, although almost all of the domatia of 5-yr-old trees contained ants

from established colonies, I also found some evidence of continued attempts by mated

queens to establish new colonies in most recently produced domatia of these older plants.

 Chi-square analysis showed that ant occupation frequency of 1-yr-old trees was

significantly different than would be expected based on the relative abundance of the four