Mating System and Facultative Parthenogenesis in the Termite Reticulitermes speratus

Both Social Hymenoptera (ants, bees and wasps) and Isoptera (termites) have independently evolved eusociality based on similar colony structures. In social Hymenoptera, queens found their colonies either solitarity or together with other newly mated queens. Males never contribute to colony foundation and social labor. In contrast to social hymenopterans, termite colony foundation usully involves both sexes. However, pairing efficiency tends to be low in the termite Reticulitermes speratus because of a limited mate-searching range, the female-biased sex ratio and a relatively low calling ability. Recently, facultative parthenogenesis was revealed to have important adaptive significance in R. speratus. Female alates that fail to pair with males found colonies cooperatively with partner females or even alone and reproduce by parthenogenesis in this species. Even female-female coopertion promotes colony foundation success if pairing with males is not possible. Facultative parthenogenesis is advantageous, even if ultimayely it may be inferior to sexual reproduction in terms of long term fitness. It enables female to reproduce in the event that a mating partner cannot be found. Diploid female progency that reproduced by thelytokous parthenogenesis showed normal development. Chromosome observation and genetic analysis using microsatellites showed that the restoration of ploidy is accomplished terminal fusion. In this paper, I discuss asexual colony foundation, mechanism of terminate parthenogenesis, selection factors for the evolution of parthenogenesis and the costs of asexual reproduction.