RICHNESS AND SEASONAL-VARIATION OF ANT-PLANT ASSOCIATIONS MEDIATED BYPLANT-DERIVED FOOD RESOURCES IN THE SEMIARID ZAPOTITLAN VALLEY, MEXICO

We quantified the frequency and seasonal variation of ant-plant associ ations mediated by plant-derived food sources, and the intensity of th eir use by ants. Thirteen ant species and 42 plant species were relate d in 135 pairs of associations. The plant families Leguminosae and the Cactaceae were those most visited by ants. The ants Camponotus rubrit horax ax (28 species) and Crematogaster opaca (16 species) used the mo st plant species as food sources. No obligatory ant-plant associations were found. Ant species studied did not use all food resources availa ble to them, resulting in a significant differential choice of food re sources; using nectar from plant reproductive structures and floral ne ctar more and extrafloral nectar less. Ant-plant asociations were more frequent during the warm, humid months, when weather conditions are m ilder, most plants are producing new vegetative growth, many are in fl ower or fruit and other insects increase their activities. Thus, ants can diversify their foraging activities. Ants are less active during t he coldest and driest time of the year. The generalized linear model f itted to the ant-plant interactions curve explained 80% of the variati on. This variation is explained by temperature alone; precipitation an d the interaction of the two factors were not significant.