Host preference and survival in selected lines of a Drosophila parasitoid,Asobara tabida

Host selection behaviour of parasitoids has important fitness consequences, if hosts of different quality are available. Here the host selection behav iour, the ability to distinguish between hosts differing in their suitabili ty, of the Drosophila parasitizing wasp Asobara tabida was studied. Females from five lines selected for higher survival in the encapsulating host spe cies D. melanogaster (Kraaijeveld et al., 2001) were compared with females from control lines. Females from all five selected lines more readily accep ted the encapsulating host species for oviposition when offered together wi th a nonencapsulating host species than females from the control lines. We found no evidence for pleiotropic effects and suggest that host selection b ehaviour evolved parallel to the ability to escape encapsulation in the hos ts. Our results also suggest that given the appropriate selection pressures , host selection behaviour can quickly evolve in parasitoids, enabling them to adapt fast to changing circumstances.