Kin recognition and larval cannibalism by adult females in specialist predaceous mites

Abstract

We investigated kin discrimination of larvae by adult cannibalistic females in two specialist predaceous mite species. In dual choice tests, adult Phytoseiulus persimilis and P.macropilis females discriminated between related and unrelated larvae and preferentially preyed upon the latter. We found little variation amongP.persimilis strains. Laboratory-reared, commercially mass-reared and field-collected females showed similar propensities to preferentially consume unrelated larvae. Due to the consistent trend in kin recognition and cannibalism among strains we dismiss that kin recognition was an artefact of rearing conditions. With respect to the production component of kin recognition, our study indicates genetic rather than environmental origin of the recognition label. Potential functional explanations for kin recognition and avoidance of kin cannibalism in the specialist predaceous mites P.persimilis and P.macropilis include epiphenomenon of species recognition, disease transmission and kin-selected behaviour. Because previous studies indicated that P.persimilis and P.macropilis do not discriminate between con- and heterospecific predaceous mites, we suggest that kin-selected behaviour is the most likely explanation. Eating related larvae may decrease the inclusive fitness of the cannibalistic female if there is an alternative way of obtaining nutrients (i.e. eating unrelated larvae). Furthermore, adult females may gain in inclusive fitness by releasing offspring from intraspecific competition for food and space and the potential threat of conspecific predators. Finally, we discuss the potential linkage between the evolution of kin recognition in specialist predaceous mites and the occurrence of aggregations of conspecific individuals.