Lab rearing environment perturbs social traits: a case study withPolisteswasps

Abstract

Laboratory-based animal rearing is a common tool used to control environmental variation. However, important differences between lab and field environments may affect the biological relevance of results. Moreover, how lab rearing affects social dynamics in groups has received little attention. We investigated the effects of lab rearing on gene expression, physiology, behavior, and colony dynamics in a behavioral model system. The primitively eusocial paper wasp Polistes fuscatus has been studied in both lab and field and is an important system for understanding social evolution and caste (queen vs. worker) development. High nourishment has been implicated as a key factor in the development of prequeen (“gyne”) traits. Because the nutritional environment is altered in the lab, understanding the effects of lab rearing on caste-related traits is critical to properly interpreting experimental results. Lab-reared wasps have access to ad lib food, whereas field colonies are likely food-limited. Our results support the hypothesis that lab rearing (and associated excess nourishment) biased the development of wasp physiology and to some extent, behavior, toward being more gyne-like. Expression levels of 4 caste-related genes, however, were in the opposite direction, toward more worker-like. Lab rearing also affected colony traits: lab-reared colonies dramatically halted nest construction and began producing male eggs 1 week later than field-reared colonies. These results demonstrate the complex effects of lab-rearing on eco-physiological traits of social species, and we discuss some pros and cons of studying ecological model systems in both lab and field settings.