LIFE-HISTORY STRATEGIES AND THE EFFECTIVENESS OF SEXUAL SELECTION
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The potential effectiveness of sexual selection depends not only on the relative survivorship of immature stages, but also on other components of fitness. The effects of fecundity and timing of maturation must be evaluated together with the survivorship in order to determine the responsiveness of alternative life-history configurations to the force of sexual selection. The r-K continuum is an inadequate model for comparisons of life-history strategies. A general three-dimensional demographic model provides a more comprehensive conceptual framework for life-history comparisons. The three-parameter demographic model is similar to several earlier two-dimensional life-history schemes and appears to describe a broad spectrum of the life-history strategies exhibited in nature. Most higher taxa tend to be dominated by only one or two of the three endpoint strategies: "equilibrium' (large investment in relatively few individual offspring), "opportunistic' (small size and rapid maturation), and "periodic' (pulsed production of large numbers of small offspring). A survey of teleost fishes and examples from several other higher taxa supports McLain's (1991) contention that the strength of sexual selection is influenced by life-history strategy. Conspicuous males are common among relative equilibrium and opportunistic strategists, but are essentially absent among species associated with the high fecundity, periodic reproductive strategy. The absence of sexually selected traits in high-fecundity broadcast spawners implies that differential survivorship among immature life stages is nonrandom in all cases. -from Author
