The neglected sex: male reproductive interests and sexual selection in social insects

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Ants and other social Hymenoptera exhibit a unique sex life which might allow testing predictions from sexual selection theory. For example, females produce large numbers of sterile workers before rearing sexuals and do not re-mate later in life, which at least in theory makes any male attempts to manipulate female fecundity at the cost of female longevity futile and minimizes sexual conflict.Furthermore, because of sperm limitation, males should be extremely choosy about the female they mate with.Despite of these unusual and interesting features, mating in social insects is remarkably littleunderstood. In our project we have set out to examine and describe various aspects of thereproductive biology of the ant Leptothorax gredleriand related species. Combining chemical, genetic, histological, and behavioural approaches we documented thata) male and female sexuals are choosy at least in that they avoid mating with related individuals, which they presumably recognize through the colony-specificity of cuticular hydrocarbon patterns in both sexes, b) females are presumably capable of sperm selection, because males transfer sperm during copulation into the female's bursa copulatrix, from where it very slowly migrates into the spermatheca through an extremely narrow constriction in the spermathecal duct, c) the gelatinous spermatophore transmitted by males during copulation prevents the loss of sperm from the female's vagina but does not prevent mating with other males, d) male accessory gland proteins are conserved among species, which is in accordance with the lack of sexual conflict, e) the length of sperm cells varies between different species with the presumed extent of sperm competition. In a last phase of this project we intend to complete a recently begun analysis of the proteins found in the accessory gland secretions, using PCR-based suppression subtractive hybridization. This shall help to learn more about the nature of the proteins that the male transfers during copulation.