Résumé
The study of mutualism is shifting from emphasizing the identification of systems that are mutualistic to attempting to understand the origin, maintenance and breakdown of mutualistic systems. Many different approaches are being used in this effort, including cost-benefit models (Roughgarden 1975), phylogenetic analyses (Thompson 1982), models of population dynamics (Addicott 1981; Wolin 1985), and the approach that we adopt in this chapter, the analysis of life-histories. We focus on two aspects of life-histories important for understanding the origin, maintenance and breakdown of mutualistic interactions: the probability of successful association between potential symbiont and host, and the comparative fitness of mutualistic and non-mutualistic symbionts when successfully associated with their host (Roughgarden 1975). More specifically, we ask two questions, (a) How does synchronization of life-cycles within and between symbiont and host populations influence the probability of successful association between mutualists and ultimately the maintenance of mutualism? (b) Under what conditions would “cheating” by potentially mutualistic individuals be favoured over strictly mutualistic behaviour? To address these questions we analyse the life-histories of species in two obligate pollination-seed prédation mutualisms: the yucca-yucca moth interaction and the fig-fig wasp interaction.