Print PageThe temperature-size rule is regarded as one of the most universal in biology, with ectotherms typically growing larger at colder temperatures. However, the robustness of this association has been challenged because the temperature-size relationship is reversed under the stressful combination of low temperature and poor diet. Significantly, the underlying nutritional basis for diet-specific responses to temperature is unknown. Nor is it known whether ectotherms might adjust their temperature selection at fine-spatial scales to optimise growth on food plants of differing quality. Such behaviour would be especially advantageous to small terrestrial animals, which have low thermal inertia and often have access to a wide range of environmental temperatures over small distances. Using the locust, Locusta migratoria, we investigated (1) the integrative effect of temperature and diet using two grasses on life history outcomes, and (2) the link between nutritional state and thermoregulatory behaviour.
Results/Conclusions
We describe the nutritional properties of two host grasses of locusts that induce differing growth responses to temperature, thereby providing the first explanation of diet ‘quality’ in relation to temperature. Next we show, locusts use fine scale patterns of movement to adjust their body temperature to meet the specific nutritional challenges posed by different host plants. Hence, ‘diet quality’ is temperature sensitive and insect herbivores can manipulate this relationship to their own ends. By adjusting body temperature for variations in the rate nutrients were supplied, locusts were able to ameliorate associated life history consequences. These findings suggest micro-climatic effects may be of more importance than previously appreciated for understanding the consequences of changed environmental temperatures and land use practices on animal-plant interactions.
