Meeting Abstract
The evolution of biological complexity is rooted in life history tradeoffs, in which beneficial change in one trait (e.g., fertility) is associated with a detrimental change in another (e.g., longevity). These tradeoffs are seen at all levels of biological organization, from single-celled and multicellular organisms to groups of cooperative individuals (i.e., a social insect colony). A universal-yet poorly understood-feature of transitions in biological complexity from the individual to a group is the decoupling of life history tradeoffs at the individual level and recoupling at the higher level. For example, queens of social insect colonies show escape from tradeoffs, as they are both long-lived and highly fertile, but these tradeoffs are recoupled at the colony level, which must balance resource allocation between colony maintenance and brood production. A potential mechanism for the life history tradeoff decoupling observed in social insect queens is a molecular rewiring of pathways linking the stress response to reproduction. Species with facultative social behavior provide a unique opportunity to test this hypothesis, because life history tradeoffs are preserved in some individuals but decoupled in others, suggesting they hold the key to how mechanisms of tradeoff decoupling impact social evolution. We experimentally manipulated reproductive investment via endocrine treatments and observed immune investment response in a facultatively social bee, Megalopta genalis by measuring response in terms of mortality, ovary maturation, and nutritional stores. By illuminating the mechanisms of life history trade-offs in a flexibly social organism, our results provide valuable insight into how physiological ecology influences life history evolution.
