This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will support a twenty-four-month research fellowship by Dr. Timothy J. Greives to work with Dr. Michaela Hau at Max Planck Institute for Ornithology in Germany and with Dr. Tom Hahn at the University of California, Davis in the US.
Seasonal cycles in reproductive activity are observed in virtually all animals, including birds. These cycles represent adaptations that ensure offspring production during favorable environmental conditions. In the temperate-zone, photoperiod (i.e., day-length) provides a ?noise-free? seasonal cue that does not vary from year to year for a given day. Hence, most species rely on photoperiod to determine the time of year. Seasonal changes in reproduction have even been demonstrated in species living in relatively stable habitats (i.e., the tropics), suggesting that selection favors a seasonal regulation of reproductive activity across latitudes. However, the nature of the selection pressures that shape gonadal cycles in vertebrates remains unknown. This has been due, in part, to methodological constraints limiting the ability to modify experimentally the timing of gonad activation in the field. This fellowship tests the hypothesis that the precise timing of reproduction has evolved in response to fitness costs associated with mistimed breeding events. The timing of gonadal activation is being advanced in free-living great tits through manipulation of perceived photoperiod using a miniature light emitting diode (LED) attached to the birds? head, providing photoperiodic stimulation prior to the start of normal gonadal development. Further, the effect of mistimed reproduction on novel neuropeptides (e.g., kisspeptin, gonadotropin-inhibitory hormone) is being examined; this will enable a better understanding of their specific roles in regulating vertebrate reproduction. In Experiment 1, behavior, reproductive success and survival rates are being documented in breeding pairs. In Experiment 2, neuroendocrine responses to precocious photoperiodic stimulation will be investigated using state-of-the-art techniques. The proposed experiments are the first to advance gonadal development using photoperiod manipulation in a free-living vertebrate to quantify resulting effects on fitness.
Understanding the selection pressures that act on mistimed seasonal processes will help to resolve the question of why most avian species, and a large number of vertebrates world-wide, exhibit pronounced cycles in gonad size. They will also provide a unique opportunity to elucidate mechanisms by which diverse environmental cues are integrated within the brain. The knowledge generated will be useful in understanding the underlying processes (both ultimate and proximate) shaping the ability of populations and species to respond to global climate change or spread to new habitats.
