Beyond fecundity and longevity: trade‐offs between reproduction and survival mediated by behavioural responses of the seed beetle, Callosobruchus maculatus

Abstract. Many studies of life‐history traits have failed to find trade‐offs where they are predicted by theory. A hypothesis that explains the lack of trade‐offs between fecundity and longevity in the seed beetle, Callosobruchus maculatus , is proposed. By manipulating host availability time and host size, trade‐offs mediated by behavioural responses of the female to adapt to environmental change are tested. Females show no decrease in lifetime fecundity when host availability time is limited to only 4 h on each day. However, longevity significantly increases when the female is provided with small beans after host deprivation. Because neither acquisition, nor utilization by females of these four manipulation treatments significantly differs, studies are carried out to demonstrate whether the energy shifted from increased longevity without decreasing fecundity. Providing abundant small or large beans each day directly after host deprivation, significantly increases the number of daily eggs laid by the female for several days, whereas the female decreases the uniformity of her egg dispersion only when small beans are provided. Therefore, the female shows a response to a change in the environment by adjusting egg‐laying rate and/or egg‐dispersion pattern. This may change the traits of reproduction and survival. Because energy allocations can be shifted between components of reproduction (e.g. host‐selection behaviour and fecundity) or between reproduction and survival, fecundity and longevity may be inappropriate indices for trade‐off analyses in this study. A framework for exploring the costs of reproduction mediated by physiological and behavioural changes in C. maculatus is proposed and discussed.