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Abstract

Animals that inbreed regularly under natural conditions may provide valuable information about the evolutionary response of mate choice to an increase in a population's rate of inbreeding. I studied how an individual's inbreeding status affects its criteria of mate choice, as well as its own attractiveness, in a parasite, the hermaphroditic cestode Schistocephalus solidus, which inbreeds under natural conditions. Specifically, I tested whether a cestode's inbreeding status and allocation to reproductive tissue affect its attractiveness to selfed and outcrossed individuals. In a simultaneous choice situation, outcrossed cestodes strongly preferred an outcrossed mating partner over a selfed one, whereas selfed cestodes showed no preference with respect to the partner's inbreeding status. Both selfed and outcrossed cestodes were attracted to partners with a large combined amount of male and female reproductive tissue and with the potential to produce large eggs. I discuss how assortative mating with respect to inbreeding status may have consequences for the maintenance of a genetic load in the population as well as for the maintenance of selfing.