NESTING SPACE LIMITS COLONY SIZE OF THE PLANT-ANT PSEUDOMYRMEX-CONCOLOR

The size and structure of the colony of the stinging plant-ant Pseudomyrmex concolor occupying two morphologically distinct Tachigali myrmecophytic host species was studied in order to discriminate between factors limiting the ant colony size; specific hypotheses being a) food, b) territory size and c) nesting space. From intraspecific comparisons it is suggested that the ant colony size is primarily controlled by the total domatia space offered by the host plant. The space-limited hypothesis explains why plant-ants demonstrate host-limited foraging territories. I analyse the space-limited hypothesis from the host's point-of-view by using a cost-benefit graphic model. It is suggested that domatia size can be selected in a way that increases the plant's net benefit from the mutualistic relationship.