Consumption of lipid-rich seed arils improves larval development in a Neotropical primarily carnivorous ant, Odontomachus chelifer (Ponerinae)

Abstract

Abstract:Odontomachus chelifer ants collect fallen arillate seeds of Cabralea canjerana (Meliaceae), a bird-dispersed tree of the Atlantic rain forest. In the nest the larvae are fed with the lipid-rich aril, and the viable seed is discarded. Benefits from secondary seed dispersal by ants are well documented for tropical plants, but benefits to ants from consuming vertebrate-dispersed diaspores are uncertain. Twelve captive colonies of O. chelifer were used to investigate the effect of aril consumption on larval development. Treatment colonies were supplemented with 1 g of C. canjerana arils, whereas control colonies were supplemented with 1 g of synthetic diet. Egg and larval production did not differ between experimental colonies after 5 mo. Aril-fed larvae, however, grew 3.5 times larger than those in control colonies. Essential fatty acids in the arils possibly account for improved larval development. Consumption of lipid-rich arils may be critical under scarcity of arthropod prey. Improved larval development through aril consumption confirms that this ant-seed interaction is facultatively mutualistic. This result is meaningful given the predominantly carnivorous diet of O. chelifer, and the generalized nature of ant-seed/fruit interactions in tropical forests. Whether or not benefits to larvae translate into significant gains for ant colonies is uncertain.