Oviposition preference of cabbage white butterflies in the framework of costs and benefits of interspecific herbivore associations

Abstract

When deciding where to oviposit, herbivorous insects consider: (i) the plant’s value as a food source, (ii) the risks of competing with con- and heterospecific herbivores, and (iii) the risks of parasitism and predation on the host plant. The presence of con- and/or heterospecific competitors would further affect the oviposition preference, because the preceding herbivores induce direct/indirect defences in plants against forthcoming herbivores, and thereby alter oviposition decisions. In previous studies, the abovementioned factors have not been studied in an integrative manner. We performed here a case study of this by assessing the oviposition preferences of a small white butterfly,Pieris rapae, for plants occupied by combinations of conspecific larvae, heterospecific larvae (Plutella xylostella), specialist parasitoids ofPi. rapae(Cotesia glomerata) and generalist predators (ants). We previously reported that the females showed equal preference forPl. xylostella-infested and uninfested plants. Here, we showed thatPi. rapaefemales preferred uninfested plants to conspecific-infested ones, andPl. xylostella-infested plants toPi. rapae-infested ones. We discuss these oviposition preferences ofPi. rapaefemales in the framework of costs and benefits of interspecific herbivore associations from the above point of view.