The Effects of Sperm Competition on Variability in Male Reproductive Success: Some Preliminary Analyses

Abstract

Computer simulations were used to explore the influence of sperm- competition outcomes on variability in male reproductive success. The results indicate that in polygynous mating systems, sperm competition per se does not necessarily affect variation in male reproductive success. Specifically, when all matings by males confer equal opportunities for fertilization, variability in reproductive success is unchanged by the routine occurrence of sperm competition. By contrast, sperm competition that results in fertilization skewed toward either the first or last male to copulate is capable of magnifying variability in male reproductive success. This effect may be limited to situations in which a correspondence exists between the number of mates acquired by individual males and the proportion of those matings that are of the advantageous type, that is, to situations in which males having high success in precopulatory competition also tend to prevail in sperm competition.