The effects of individual-level differences in metabolic rate on foraging behavior and life history traits in honeybees
Date
2022
Authors
Cassano, Julian, author
Naug, Dhruba, advisor
Ode, Paul, committee member
Florant, Gregory, committee member
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Abstract
Metabolic rate is the rate at which organisms process energy and is often considered as the fundamental driver of life history processes. The link between metabolic rate and life history is primarily mediated via foraging, which shapes the energy acquisition patterns of an individual. This predicts that individuals with different metabolic rates likely vary in their foraging strategies, although such links have rarely been empirically investigated in the context of optimal foraging theory - a powerful framework for understanding how animals maximize their foraging returns. Many central place foragers such as honeybees maximize their energetic efficiency rather than the rate of energetic gain, given the critical role of energetic costs on foraging decisions. We therefore tested if individuals with low or high metabolic rates differ in efficiency maximization, using genetic lines of honeybees with different metabolic rates. Our results show that low metabolic rate foragers visit more flowers during a single foraging trip and have higher energetic efficiency than high metabolic rate foragers in both low and high resource conditions. We discuss the significance of these results in the context of division of labor and the adaptive role of phenotypic diversity in metabolic rate in a social insect colony. We then tested the rate of living hypothesis in honeybees using the same phenotypic lines of bees with low and high metabolic rate and by combining it with radio frequency identification (RFID) technology and respirometry to measure life history and metabolic rate parameters, we specifically examined the relationships between metabolic rate and various parameters that define foraging behavior and life history. Our results show low repeatability of metabolic rate and an inconsistent effect of metabolic rate. While metabolic rate was negatively correlated with age of ontogenetic shift and lifespan in wild-type bees as predicted by the Rate of Living hypothesis, it did not show any correlation with foraging parameters. In the phenotypic lines, metabolic rate affected life history parameters in the opposite direction than what is predicted. This was accompanied by a strong effect of seasonal effect. We provide a likely explanation for these trends with a strong recommendation for integrating such environmental interactions in our understanding of the relationship between metabolic rate and life history.