Breed early, breed late? Molecular, neuroendocrine, and developmental mechanisms regulating timing of reproduction

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Change is and always has been constant in nature. The likelihood that species will persist, expand, or go extinct depends on their ability to employ environmental information to accurately time life-history transitions. To succeed, species need to reproduce at times of the year that are favorable for rearing offspring. In a rapidly changing environment, the level of flexibility in the mechanisms that determine when animals reproduce will play a critical role in determining population-level resilience. The research will employ cutting edge technology and experimental approaches to identify the mechanisms (molecular, neuroendocrine, and developmental) that determine when animals breed. In addition, to understanding the mechanisms that determine when animals breed in changing environments, the project will also provide education and outreach opportunities to engage communities in the conservation of migratory birds on a local to global scale.Research that integrates mechanism and function in eco-evolutionary contexts holds great promise for understanding the direction and dynamics of change in living systems. The research will synthesize the mechanisms that lead to within- and among-population differences in the timing of reproductive development. Basic insights will be provided to the fields of seasonality, neuroendocrinology, and phenotypic flexibility. The research will make use of striking differences in timing of reproduction in closely related, seasonally sympatric populations of a sparrow, the dark-eyed junco (Junco hyemalis). The junco is a species that consists of an array of migratory and resident populations known to co-occur during winter and early spring when they are exposed to the same environmental cues (e.g., day length, temperature). Despite exposure to the same environmental cues in winter and early spring, some populations delay reproduction to migrate, while others do not. This project will use seasonally sympatric juncos to 1) Achieve a deeper understanding of how genetic and epigenetic variation are translated into phenotypic variation in reproductive timing by determining the relative importance of variation in gene expression and gene sequences. 2) Test the hypothesis that, contrary to traditional models of timing, dynamic feedback from the reproductive axis plays a critical role in timing reproduction. 3) Test experimentally the hypothesis that day length experienced during development sets the day length at which reproduction begins in adults. In addition, to understanding the mechanisms that determine the migratory and reproductive timing of junco species, the project will also provide education and outreach opportunities to engage communities in the conservation of migratory birds on a local to global scale, by engaging the trainees on the project with citizen scientists. The education and outreach opportunities will be accomplished in the field and via established outreach activities with local schools.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.