Evolutionary Demography of a Bruchid Beetle. III. Correlated Responses to Selection and Phenotypic Plasticity

Abstract

Previous work showed the existence of additive genetic variation in development rate, which was negatively genetically correlated with body weight. In a selection experiment, short culture intervals were used to select for fast development rates and long culture intervals for slow development rates. It was predicted that selection in short culture intervals would result in lighter, shorter lived adults and vice versa. As predicted, selection by short culture intervals did result in lighter insects and the trend in adult longevity was in the expected direction. A subsidiary aim of the experiment was to investigate a previously unstudied aspect of the beetles' plastic response to immediate circumstances. It was predicted that adults given fresh beans would devote maximal resources to oviposition and so would have fewer resources left for personal survivorship and later oviposition. As predicted adults lived significantly longer on old than on fresh beans and late fecundity was higher in adults transferred to fresh beans from old beans than in adults transferred from fresh beans. These results are discussed in the general context of evolutionary responses to environmental heterogeneity. Key-words: Callosobruchus maculatus, fecundity, genetic correlation, indirect selection, life-history theory, longevity, phenotypic plasticity, trade-offs