Early in my career I described a pattern of movement known as differential migration in which females migrate farther than males, and I laid out hypotheses to explain why that formed the basis for decades of research by others.
Later I took an experimental approach to the evolution of life histories, which I labeled ‘phenotypic engineering.' By manipulating levels of the hormone testosterone in free-living animals and comparing their behavior, physiology, and fitness to controls, I found that males with experimentally elevated testosterone exhibited greater mating success but also greater mortality than controls. This research provided a mechanistic understanding of the fitness consequences of altering how animals allocate time and energy to competing demands. Subsequent research addressed variation in testosterone-activated gene expression in target tissues in relation to phenotypic plasticity and rapid evolution, with the ongoing goal of understanding how natural selection acts on mechanisms to give rise to adaptation.
Most recently my focus has returned to animal migrations and addressing limits to adaptive capacity and the role of seasonal timing in the generation and loss of biodiversity. I am also committed to research that will help prepare us to be resilient in the face of oncoming environmental change.