Maintaining diversity in an ant community: modeling, extending, and testing the dominance-discovery trade-off.

Ant communities often consist of many species with apparently similar niches. We present a mathematical model of the dominance-discovery trade-off, the trade-off between the abilities to find and to control resources, showing that it can in principle facilitate the coexistence of large numbers of species. Baiting studies of dominance and discovery abilities in an ant community from the Chiricahua Mountains of Arizona indicate that real communities fail to fit the assumptions of the simple model in several ways: (1) dominance depends on the size of the food resource; (2) for some ants, dominance depends on the presence or absence of specialist parasitoids; (3) pairwise dominance is not an all-or-nothing trait; and (4) a consistent negative relationship between pairwise differences in per capita discovery rates and dominance can be detected for only one bait type. Extended models incorporating these factors successfully predict the coexistence of five of the six most abundant members of this community but fail to accurately predict their relative abundances. Sensitivity analysis indicates that each complicating factor enhances the extent of coexistence.

Diptera as parasitoids.

Parasitoids in the insect order Diptera include an estimated 16,000 species, or approximately 20% of the total number of species with this life-style. Parasitoids in this order are exceedingly diverse in both their habits and evolutionary origins, which makes them an underutilized but highly suitable group for quantitative studies of character convergence and adaptive radiation. This review focuses on several aspects of the bionomics of dipteran parasitoids that have received little comprehensive treatment, including processes associated with host location and attack, patterns of host use, and the evolutionary and ecological consequences of host-parasitoid interactions. Throughout the review we contrast the patterns found within the parasitic Diptera against those found in the better studied parasitic Hymenoptera. We conclude that more intensive study of dipteran parasitoids is required before we can understand the general conditions that favor the evolution of insect parasitoids and the truly magnifying themes of their behavior and ecology.

Competition between ant species: outcome controlled by parasitic flies.

Experimental evidence demonstrates that the parasitic phorid fly Apocephalus shifts the competitive balance between the ant species Pheidole dentata and Solenopsis texana by interfering with the defensive behavior of Pheidole dentata major workers (soldiers). This represents one of the first examples of a parasite affecting competitive interactions anmong terrestrial animals in natural communities. Similar complex interactions are probably common in many ant communities.