title: Testosterone-mediated effects on fitness-related phenotypic traits and fitness.
abstract: The physiological and behavioral mechanisms underlying life-history trade-offs are a continued source of debate. Testosterone (T) is one physiological factor proposed to mediate the trade-off between reproduction and survival. We use phenotypic engineering and multiple laboratory and field fitness-related phenotypic traits to test the effects of elevated T between two bank vole Myodes glareolus groups: dominant and subordinate males. Males with naturally high T levels showed higher social status (laboratory dominance) and mobility (distance between capture sites) than low-T males, and the effect of T on immune response was also T group specific, suggesting that behavioral strategies may exist in male bank voles due to the correlated responses of T. Exogenous T enhanced social status, mate searching (polygon of capture sites), mobility, and reproductive success (relative measure of pups sired). However, exogenous T also resulted in the reduction of immune function, but only in males from the high-T group. This result may be explained either by the immunosuppression costs of T or by differential sensitivity of different behavioral strategies to steroids. Circulating T levels were found to be heritable; therefore, female bank voles would derive indirect genetic benefits via good genes from mating with males signaling dominance.
authors.affiliation: Centre of Excellence in Evolutionary Research, Jyväskylä, University of Jyväskylä, Finland. mills@sooozie.co.uk
authors.forename: Suzanne C
authors.initials: SC
authors.lastname: Mills
authors.forename: Alessandro
authors.initials: A
authors.lastname: Grapputo
authors.forename: Ilmari
authors.initials: I
authors.lastname: Jokinen
authors.forename: Esa
authors.initials: E
authors.lastname: Koskela
authors.forename: Tapio
authors.initials: T
authors.lastname: Mappes
authors.forename: Tuula A
authors.initials: TA
authors.lastname: Oksanen
authors.forename: Tanja
authors.initials: T
authors.lastname: Poikonen
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood; D003411:Arvicolinae / Q000276:immunology / Q000502:physiology*; D005387:Finland; D006608:Hierarchy, Social; D007074:Immunoglobulin G / Q000097:blood; D016014:Linear Models; D008297:Male; D010641:Phenotype; D011863:Radioimmunoassay; D013037:Spatial Behavior / Q000502:physiology*; D013045:Species Specificity; D016019:Survival Analysis; D013739:Testosterone / Q000097:blood / Q000276:immunology / Q000502:physiology*
chemical_list: D000906:Antibodies; D007074:Immunoglobulin G; D013739:Testosterone