Body size sexual dimorphism affects mating behaviour in the parasitoid wasp, Lysiphlebus fabarum (Braconidae: Aphidiinae).

Body size has a profound effect on many aspects of animals' biology including sexual interactions. Hymenopteran parasitoids exhibit dimorphisms in which females are larger than males. A recent study has indicated that in the solitary koinobiont parasitoid wasp Lysiphlebus fabarum Marshall, offspring life history traits are influenced by maternal body size, which raises the questions of whether larger females are preferred and whether larger males have an advantage when it comes to accessing larger mates. To test this, females of L. fabarum were allowed to lay eggs in aphids (Aphis fabae Scopoli) at different growth stages to manipulate female and male body size. First, we conducted a choice experiment to determine whether large female wasps are preferred by males. Secondly, we examined the effect of male body size on the ability of males within a patch to access females. Males of L. fabarum lack mate preference, as both small and large females were almost equally selected as mates. Mate searching duration did not vary with male or female body size, suggesting that body size would not influence pre-copulatory interactions within the patch. Smaller males copulated significantly longer, and copulation duration increased with the sexual body size dimorphism. Our finding suggests that a "first-to-mate" strategy is favoured by males, mating with the female they encounter regardless of her quality. Also, small males copulate longer possibly because of lower sperm transfer rate. This study shed light on the evolutionary processes regarding mating behaviours in this parasitoid wasp. [ABSTRACT FROM AUTHOR]