Abstract
Polyphagy implies that a species can consume and utilise many different prey types but whether this phenomenon applies to any individual or to a collection of otherwise choosy individuals, is not known. Analysis of prey preference and associated reproductive success in a soil-inhabiting predatory mite (Hypoaspis aculeifer) showed that genetic variation in preference for two prey species (bulb mites and copra mites) does exist, that this variation occurs in the field at a very small spatial scale, that the preference trait is inherited as if it is determined by one gene, and that the preference polymorphism is not maintained by niche differentiation, but by a combination of hybrid superiority and disassortative mating (Lesna and Sabelis, Nature, Oct. 1999). When the prey diet offered was such that hybrids were less successful than parental lines, the predatory mites switched to assortative mating. We hypothesise that local polymorphisms in preference result from the presence of genetic constraints and its consequences for mate choice. To verify and generalise this hypothesis, we propose two lines of research. We intend to critically test the assumptions underlying the hypothesis (Can genetic constraints be overcome? Can we select for a "Masters of all Trades"?) and the emerging predictions (Does mate choice always depend on reproductive success of hybrids vs parental lines?). Moreover, we plan to extend the analysis <f preference genetics and reproductive success to other prey species (nematodes, springtails, thrips, fly larvae). In this way the genetic architecture underlying polyphagy may be unravelled in this predatory mite, which may stimulate further research into the ecology and evolution of specialists and generalists and the maintenance of genetic polymorphisms through hybrid vigour .
Netherlands