Evol Ecol Res 2: 15-28 (2000)     Full PDF if your library subscribes.

The selection of social actions in families: II. Parental investment

David G. Lloyd

Department of Plant and Microbial Sciences, University of Canterbury, Christchurch, New Zealand


One of the most widely used applications of kin selection concerns the investment that parents provide to their young. In particular, Trivers’ concept of parent–offspring conflict was enthusiastically adopted by biologists and applied to many aspects of parent–offspring interactions, including reproductive effort, clutch size, brood reduction, sex ratios, and dispersal and germination strategies. In this paper, parental and offspring strategies are examined with regard to the amount of resources that parents invest in each offspring; this determines the size and average fitness of the newly independent young. Parental investment is used here as a model system to compare the results of genetic models of social actions with those of autonomous gene models, and to examine the relative merits of using measures of inclusive or collective fitness. To this end, the extent of conflicts over parental investment is derived for two kinds of families, which differ in the way that the young compete with each other (equal versus unequal competition). Finally, the ways in which conflicts are resolved and the relative importance of conflict and cooperation in raising young are discussed.

Keywords: collective fitness, inclusive fitness, kin selection, parent–offspring conflict.

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