EAGER: Pace of Life as an emergent outcome of variation in metabolic rate at a lower level of organization

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Individuals of different species, as well as individuals within a species, can differ in their life history along a slow-fast continuum such that those showing slower growth and delayed reproduction but higher survival are said to have a slow pace of life while those with faster growth and early reproduction with lower survival are said to have a fast pace of life. Since metabolic rate determines the rate at which an animal acquires and spends energy, it has often been considered the fundamental driver of pace of life. The influence of metabolic rate on pace of life can be complex. A higher metabolic rate, by allowing more activity and resource acquisition, can lead to a faster pace of life, but, burning more energy can also lead to a slower pace of life. Studies investigating the relationship between metabolic rate and pace of life often produce ambiguous results. The broad objective of this research is to select genetic lines of honeybees with different metabolic rates and experimentally test how differences in metabolic rate interact with resource availability to determine pace of life. Using the honeybee colony as an experimental model allows an understanding of not only how metabolic rate determines pace of life at the individual level but also how interindividual variation in metabolic rate determines pace of life at the colony level. Understanding this important relationship between metabolic rate and life history can contribute to biomedical sciences as metabolic rate critically influences various health parameters. The development and maintenance of genetic lines of bees with different metabolic rate will also be a novel biological resource for research and potentially to the beekeeping industry.Metabolic rate (MR) is often considered the fundamental rate that drives all biological processes at all levels of biological organization. A central question in biology therefore is how the functional properties at any level of organization are determined by the MR of its constituent parts. By selecting and breeding genetic lines of honeybees with different MR and creating colonies with different metabolic (rate) compositions, this research will provide an experimental test of the relationship between MR and pace of life (POL) at the individual and the colony level. The project will use an integrative approach based in genetics, physiology and behavior to ask how MR of an individual impacts its POL and its social contribution, how the POL at a group level is determined by the MR and POL of its individual members, and how MR interacts with the resource environment to regulate individual and colony POL. The integrative experimental approach combined with path analysis will allow a causal test of the connection between MR and POL, providing answers regarding the functional links that connects physiology to life history evolution. By combining measurements of MR with economic analysis of individual work contribution in a social insect colony, the research will add to our understanding regarding how interindividual variation in MR and POL scale up to drive POL at a higher level of biological organization in the evolution of eusociality.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.