Association between feeding rate and parasitoid resistance in Drosophila melanogaster

Replicate lines of Drosophila melanogaster have been selected for increased resistance against one of two species of parasitoid wasp, Asobara tabida a nd Leptopilina boulardi. In both cases, it has been shown that an improved ability to mount an immunological defense against the parasitoid's egg is a ssociated with reduced survival when the larvae are reared under conditions of low resource availability and thus high competition. We show here that in both sets of selected lines, lower competitive ability is associated wit h reduced rates of larval feeding, as measured by the frequency of retracti ons of the cephalopharyngeal skeleton. This suggests that the same or simil ar physiological processes are involved in the trade-off between competitio n and resistance against either parasitoid and shows how the interaction be tween adaptations for competition and natural enemy resistance may be media ted.