Foraging behavior of Atta sexdens (Hymenoptera, Formicidae) on leaves of Thiloa glaucocarpa (Mart.) Eichler (Combretaceae) in a Brazilian seasonally dry tropical forest

Abstract

Thiloa glaucocarpa is a toxic plant as a food item for bovine cattle. However, dry leaves are frequently collected to cultivate the symbiotic fungi of several colonies of Atta sexdens throughout the Caatinga Seasonally Dry Tropical Forest biome in Brazil and such behavior is not clear. In this study, we analyzed the removal of T. glaucocarpa leaves for A. sexdens and tested the hypothesis that the preference for removal of dry leaf material over fresh leaves may be related to the decay of chemical defenses. Dried leaf discs of T. glaucocarpa were offered to laboratory-raised colonies of A. sexdens. Overall, there was a lower consumption of T. glaucocarpa than the previous report, but it is possible to observe a preference for mature and fresh leaves removal, contradicting initial predictions. Probably, the removal of dried leaves is a specific solution learned by natural colonies to reduce the number of secondary compounds and guarantee diet availability in a highly seasonal and food-poor environment. The preference for mature leaves is not usual and is probably the result of a higher production of secondary compounds in young leaves, which could guarantee protection for leaves against herbivory in early rains and improve the productivity of T. glaucocarpa at the beginning of the rainy season.