Limits on optimal decision making: host plant selection is not altered by high temperatures in a butterfly

Abstract

Plastic behavioural adjustments represent a powerful mechanism for animals to respond to severe environmental changes. For instance, animals may use distinct resources, which could enhance their fitness, because of increased temperatures. Such shifts in resource use may be observed in egg laying female insects, modifying host plant preference under challenging conditions. Indeed, females are expected to increase their selectivity towards high-quality host plants when experiencing high compared with benign temperatures. In this study, we examined whether female Bicyclus anynana butterflies can enhance their reproductive performance by modifying host plant use in response to challenging temperature regimes. Towards this end, we investigated (1) whether exposure to variable thermal conditions affected reproductive output when females had access to only one host plant, and (2) whether this in turn affected the oviposition preference for host plants of different quality under laboratory conditions. We expected hot conditions to reduce the reproductive performance (egg number, offspring survival and performance) of butterflies. Such deleterious effects may, however, be counterbalanced by a higher selectivity for high-quality plants when females have simultaneous access to plants of different quality. We found that the reproductive performance of butterflies was indeed reduced when they experienced hot conditions. These temperature effects were only observed when butterflies only had access to a low-quality plant. However, individuals did not increase their selectivity towards the higher-quality host plant in response to hot conditions, possibly because of fecundity costs associated with increased choosiness. Our results illustrate the limits of plastic behavioural adjustments in response to changing environmental conditions under laboratory conditions. Further studies are, however, necessary to clarify whether this lack of plasticity is also observed in wild animals, which may limit their adaptability in the face of climate change. • Female butterflies lay fewer eggs on low-quality host plants under hot conditions. • Butterflies did not target plants of better quality under hot conditions. • This lack of selectivity probably results from its associated fecundity costs.