Meeting Abstract
125.1 Tuesday, Jan. 7 14:00 Shift in a life history trade-off linked with change in hormonal cross-talk ABOLINS-ABOLS, M*; KETTERSON, E D; Indiana University, Bloomington; Indiana University, Bloomington mabolins@indiana.edu
Perhaps the most fundamental life history trade-off is that between reproduction and self-maintenance. This trade-off is mediated by the interaction of two major endocrine systems, the hypothalamic-pituitary-gonadal (HPG) axis, which regulates reproduction, and the hypothalamic-pituitary-adrenal (HPA) axis, which regulates metabolism and the stress response. Environmental change may alter optimal allocation of resources to reproduction and self-maintenance, shifting the trade-off, thus giving rise to selection on the interaction of the HPA and HPG axes. Recent independent colonization events of an urban environment by the typically mountain-breeding Oregon junco (Junco hyemalis thurberi) in California has dramatically altered timing of breeding and stress ecology, resulting in increased allocation to reproduction and reduced response to stressors. We investigated the direction and strength of the interaction between the HPA and HPG axes in two locations of recent independent montane-urban colonization events. We injected wild birds with corticotropin releasing hormone (CRH), a major activator of the HPA axis, and measured corticosterone. We then injected birds with of gonadotropin releasing hormone (GnRH), a major activator of the HPG axis, and measured testosterone. We will compare and contrast findings from the two city-mountain comparisons and show that in at least one colonization event, CRH negatively affects the ability of birds to release testosterone in the mountain population but not in the city population, indicating greater sensitivity to stressors on reproduction in the mountain population. Interestingly, corticosterone and testosterone are positively, not negatively, correlated in both populations. We conclude that hormonal interactions are plastic, complex, and reflective of environmentally induced changes in life-history trade-offs.
