Meeting Abstract

S3.5  Sunday, Jan. 4  Hormones and Performance: Insights from Natural History and Endocrine Manipulations JOHN-ALDER, H.B.*; COX, R.M.; HAENEL, G.J.; SMITH, L.C.; Rutgers Univ., New Brunswick, NJ; Dartmouth Col., Hanover, NH; Elon Univ., Elon, NC; Richard Stockton Col., Pomona, NJ henry@aesop.rutgers.edu

Whole-animal performance, defined as the ability to accomplish ecologically relevant tasks, represents the integration of morphological, physiological, and behavioral traits and is thus an obvious target of endocrine regulation. Hormonal control of performance can be identified in a top-down approach beginning with studies of natural history followed by experimental endocrine manipulations to establish functional relationships. We investigated seasonal, sexual, and developmental variation in growth and exercise performance in field-active Sceloporus lizards to find candidate hormonal regulators and to inform the context and design of subsequent endocrine experiments. Further, we undertook focal observations and demographic studies coupled with determinations of paternity in the field to test associations between performance traits and measures of fitness. In S. undulatus, seasonal variation in running endurance, home range activity, and breeding behavior are associated with variation in plasma testosterone and corticosterone, and in both female-larger and male-larger species of Sceloporus, sex differences in growth are associated with sexual divergence in plasma testosterone. In experimental studies, testosterone enhances running endurance and its underlying physiological support as well as home range activity, and, depending on the species, testosterone either stimulates or inhibits male growth. Running endurance and body size help to determine a male lizards ability to patrol home range and gain access to potential mates. Our studies exemplify the power of natural history combined with endocrine manipulations to identify testosterone as a regulator of performance traits linked to fitness.