GnRH1 neuron activation regulates the seasonal reproductive timing in a North American songbird (RPA Pilot / Seed Project)

Several studies have investigated the role of photoperiodic time measurement in avian seasonal reproduction, but a population-level comparison that investigates all neuroendocrine mechanistic events that underlie seasonal reproductive timing has been lacking. Research to be carried out under this proposal will compare neuroendocrine responses in day length perception, phototransduction, and transformation of photic information in populations that live in sympatry during the nonbreeding season but breed at different latitudes. Completion of the objectives proposed in this proposal will provide valuable insights into the ways that environmental conditions, particularly photoperiod experienced during gonadal recrudescence, define the timing of seasonal reproductive response with implications for the future fitness of populations and even the maintenance of the biodiversity. By quantifying mechanistic variation at neuroendocrine levels among natural populations that differ in reproductive phenology, some breeding early and some breeding later, we propose the following aim: We will study how early- and late breeding populations at their population-specific critical photoperiods differ in GnRH synthesis and GnRH neuron activation in response to activation of the neuroendocrine axis.