A Latitudinal Gradient in Rates of Ant Predation

Predation by ants on wasp larva baits was assessed at five latitudes from 43°N to 2°S. Rates of predation were significantly greater in the tropics; that is, a food item was exploited by ants in significantly less time in the tropics than in the temperate zone. It was also found that predation rates were higher in low second—growth vegetation than in forests and higher on the ground than on vegetation, and that these differences were more pronounced in the temperature zone than in the tropics. Rates of predation occuring on buildings were lower than in natural situations at every latitude. The number of ant species taken at the baits increased from 22 at the northernmost locality to 74 at the southernmost. In all localities but the northernmost the forest habitat produced a greater diversity of species than the field habitat. There was greater degree of microhabitat specificity among ants in the tropics than in the temperate zone. The proportion of forest canopy specialists also increased toward the tropics. Overall predation rate and ant species richness were found to be positively correlated on a latitudinal scale, but this relationship broke down at the level of habitats and microhabitats.