Sexual and Asexual Reproduction

The concept of fecundity should, in practice, be applied equally to the two major modes of reproduction - sexual and asexual. Discussions centered on the evolution of sexual reproduction must reconcile the theoretical advantage asexual reproduction presents to an individual - the possibility of a twofold fitness (fecundity) advantage over their sexual counterparts. The relatively higher cost of sexual reproduction arises from anisogamy (gamete dimorphism), but sexual selection can reduce or even eliminate this cost. Although there is no difference in the fecundity of sexual females and asexuals of the same genotype, the equilibrium frequency of deleterious mutations is lower in sexual populations, usually giving rise to higher fitness in sexual females.

Despite the advantages of sexual reproduction, the prevalence of clonal or asexual reproduction in the life histories of many plant and animal species suggests that this strategy does indeed provide advantages at least in some circumstances. For example, clonal reproduction may allow the clone to survive many reproductive events by reducing a potentially catastrophic local extinction associated with a restricted distribution. A large number of clone-mates may also increase the number of bodies producing gametes and improve the probability of them finding mates once sexual reproduction is invoked. Thus, variation in the costs and benefits ofclones should depend on an individual's sexual neighborhood (relative abundance of potential mates) and the degree of competitive stress induced by the environment.

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