Carrying capacity, competition and maintenance of sexuality

A modification of the logistic equation is critically analysed and its application to competition between sexual and asexual populations presented. Such a model of competition can be a formal representation of the tangled bank hypothesis of the evolution and maintenance of sexuality. It shows that the elimination of asexual individuals by sexual ones is possible only if the size of the habitat or the width of the ecological niche of sexual individuals is twice as large as that of asexual ones. Co-existence of these two forms is theoretically possible under much less rigid conditions. Nevertheless, such co-existence does not imply that the ecological cost of the elimination of asexual individuals by sexual ones is lower than the commonly accepted biological cost of such elimination.