Effect of ant-attendance on the occurrence of intraguild predation

Abstract

Parasitoids and predators exploiting similar food resource make aphidophagous guilds especially favourable systems for studying intraguild predation, but ants as third parties protect aphids against their natural enemies and in return obtain carbohydrate-rich honeydew as a nutritional resource. A field experiment on the interrelationship among aphids, ants and predators/parasitoids was conducted on two plants (hoary cress Cardaria draba L. [Brassicaceae) and Canada thistle Cirsium arvense L. [Asteraceae]). Cardaria was infested with the aphid Acyrthosiphon gossypii Mordvilko (Homoptera: Aphididae) tended by the ant Lasius turcicus Santschi (Hymenoptera: Formicidae). Cirsium was infested with the aphid Brachycaudus cardui L. (Homoptera: Aphididae) tended by the ant Crematogaster sordidula Nylander (Hymenoptera: Formicidae). The mean number of predators per aphid colony decreased significantly when the aphids were tended by ants on both host plants. In contrast, the parasitism rate of both aphids decreased significantly without the tending ant. Thus ant attendance can affect the occurrence and intensity of intraguild predation, and consequently provide enemy free space for parasitoids. If a foraging female aphid parasitoid succeeds in ovipositing into patches with guarding ants, then its offspring could be protected from the risk of intraguild predation.