Ecological Archives E092-004-A2

Elizabeth G. Pringle, Rodolfo Dirzo, and Deborah M. Gordon. 2011. Indirect benefits of symbiotic coccoids for an ant-defended myrmecophytic tree. Ecology 92:37–46.

Appendix B. Estimation of colony-size variables from estimator domatia.

To estimate colony sizes for additional trees from each site, three subterminal “estimator” domatia were collected from the six trees per site for which colonies were fully counted, and from an additional 14 trees per site of heights 2-8 m.  Domatia were collected during rain or after spraying with water.  Each domatium was collected in a single vial and frozen for 12 hrs.  Each domatium was then measured, and ant workers and coccoids were counted.  The total number of domatia for each tree was estimated using the coefficient derived from the linear relationship, for 12 trees at each site, between the sum of basal diameter and diameter at breast height (DBH), measured at 1.4 m, and the number of domatia (Table B1).  To estimate nesting space, colony size, and the number of coccoids in the entire tree, we added measurements from the three collected domatia, and then multiplied these sums by the proportion of the total domatia in the tree represented by those three.  These initial estimates were then multiplied by the coefficient of the linear relationship between estimated and observed values from the six trees per site that were collected, to obtain final, corrected estimates (Table B2).

TABLE B1. Relationships between diameters and the number of domatia in 12 trees at each site.

Site R2 df F P Equation through the origin
Chamela 0.66 11 19.16 0.002 # Domatia = 7.6(Basal+DBH)
Santa Rosa 0.70 11 23.82 0.0006 # Domatia = 13.5(Basal+DBH)

TABLE B2. Error of colony-size estimates from sample domatia.

Variable Site R2 df F P Equation through the origin
Space   Chamela 0.91 5 42.32 0.003 Measured space = 1.4(estimated space)
Santa Rosa 0.92 5 47.93 0.003 Measured space = 1.1(estimated space)
Worker ants   Chamela 0.94 5 67.95 0.002 Measured ant count = 0.8(estimated ants)
Santa Rosa 0.54 5 4.71 0.10 Measured ant count = 0.8(estimated ants)
Coccoids   Chamela 0.97 5 117.93 0.0004 Measured coccoid count = 0.6(estimated coccoids)
Santa Rosa 0.66 5 7.66 0.05 Measured coccoid count = 0.6(estimated coccoids)

[Back to E092-004]