Ce. setulifer which occupied 48 of the 49 domatia on the plant; one domatium on this tree

was uninhabited.

 Ant species displayed non-random within-plant microhabitat occupancy in both

the 2- and 5-yr-old plants (x2 = 133.1, df = 4, P < 0.0001 and x2 = 76.81, df = 3, P <

0.0001, respectively). In the 2-yr-old plants, A. pittieri had a significantly higher

habitation frequency in branches from the upper stratum of C. alliodora plants (x =

32.35, df = 2, P < 0.0001), whereas Cr. carinata had a higher habitation frequency for the

lower, older branches (x2 = 90.26, df = 2, P < 0.0001). Cephalotes setulifer displayed a

non-random pattern of occupancy in the three strata (x = 10.43, df = 2, P = 0.005), but no

clear directional trend was evident (Fig. 2-2a). However, in the 5-yr-old plants, Ce.

setulifer was significantly more common in the younger terminal or subterminal domatia

than expected by chance (x2 = 56.47, df= 1, P < 0.0001). In these older plants, Cr.

carinata exhibited no difference in occupation frequency in different parts of the tree (X2

= 0, df = 1, P = 1), and both A. pittieri and P. fortis were less common than expected in

terminal or subterminal domatia (x2 = 4.64, df = 1, P = 0.033 and x2 = 15.69, df = 1, P <

0.0001, respectively; Fig. 2-2b).

 The relationship among the occupation patterns of the two numerically dominant

species, A. pittieri and Cr. carinata, and the third most abundant species, Ce. setulifer,

changed substantially over the ontogeny of the symbiosis. Aztecapittieri and Cr.

carinata coexisted in many 1-yr-old plants and on eight of the nine 2-yr-old plants.

However, they were mutually exclusive, with the exception of a single foundress queen

of A. pittieri on one tree dominated by Cr. carinata, by the time trees were 5 years old.

These two dominant ant species showed markedly different occupation strategies (Fig. 2-