Research

Overview: We are an interdisciplinary lab interested in understanding how animals live in environments that are continually and predictably changing on daily and annual time scales by asking:

1) What are the underlying physiological, neural, and genetic mechanisms used by animals to integrate environmental information to fine-tune timing of changes in behavior and physiology to optimize temporally available resources (i.e. seasonal food pulses, access to mates)?

2) What are the selective pressures that have shaped these mechanisms?

3) And how does knowledge of these underlying mechanisms inform our understanding of why some animals are able to cope with changes in their environments (i.e. urbanization and climate change) while others are not.

Seasonal timing: As the environment changes, animals must adjust the timing and expression of their life-history transitions, including reproduction and migration, to keep pace. Identifying the underlying physiological phenotypes that selection may act on linking timing decisions with reproductive success is needed; yet, to date researchers have failed to link individual variation in physiological traits (e.g., baseline gonadotropin hormone levels) with timing decisions (e.g., egg laying) and reproductive success in the wild. Further, in many species, including birds, female timing decisions are ultimately responsible for dictating the time of year when rearing of offspring will occur, yet physiological mechanisms influencing female reproductive timing decisions in free living animals are seriously lacking. To begin to address these important questions we, in collaboration with Dr. Ellen Ketterson from Indiana University are exploring differences in physiology between two groups of birds of the same species that differ in their reproductive responses under the same environmental conditions. Recently, we have also initiated a project to better understand how variation in location and habitat where a bird overwinters may influence springtime reproductive timing decisions.

Daily timing: Nearly all organisms possess daily (i.e., circadian) rhythms. It is hypothesized that these rhythms provide a fitness advantage by enabling organisms to alter physiology and behavior in anticipation of diel changes in the environment and thereby maximizing reproduction and survival; however, this hypothesis remains relatively unexplored in animals. At present, the very few examples exploring selective forces capable of acting on circadian rhythms have focused primarily on the survival value (i.e. risk of depredation) of these rhythms. The relationship between these rhythms and reproductive success remains still relatively unexplored, particularly in the wild. Using the great wealth of knowledge generated in laboratories over the last several decades of the neural and endocrine control of circadian rhythms allows for informed manipulations of these rhythms in the wild so we can ask what their ecological and evolutionary significance is. Recent work by our group suggests a role for properly functioning circadian rhythms on reproductive success, an important component of fitness: male birds receiving continuous release melatonin implants which is known to weaken circadian rhythms in the lab, were more likely to be cuckolded. The ability to gain extra-pair offspring and preventing cuckoldry greatly influences an individual’s reproductive success and thus its fitness. We are currently investigating the role individual variation in sex steroid hormones play in influencing these daily rhythms.