Sierra Nevada Aquatic Research Laboratory

01 May, 06 AM - 31 Jul, 06 AM

A central question in life-history theory involves what factors control reproductive effort, or the fraction of the available resource base devoted to reproduction. Since Williams (1966), theorists have recognized that the optimal level of reproductive effort depends on balancing the tradeoff between current reproductive effort and future survival and reproduction. More recently, McNamara and Houston (1992, 1996) developed a state-dependent approach to life-history theory, which recognizes that life-history optimums shift with changes in environmental conditions and physiological state. In state-dependent life-history theory, optimal levels of reproductive effort are described as reaction norms that express how reproductive effort changes along environmental or physiological gradients. In vertebrates, the adrenocortical stress response mediates responses to perturbations by promoting survival over reproduction. Given high future reproductive potential, activation of the stress response, and release of glucocorticoids (GCs), adaptively shifts investment toward survival. Conversely, given limited future reproductive potential, fitness may be elevated by suppressing the stress response and maintaining reproductive activity. If GCs modulate the amount of risk that individuals are willing to accept to either themselves or their offspring, a link between GCs and plasticity in reproductive effort is expected. However, no study has examined whether variation in the stress response is associated with differences in how individuals adjust reproductive effort in response to perturbations that poise a risk to adult survival or the current reproductive episode. I will address this question by manipulating perceived nest and adult predation risk in song sparrows (Melospiza melodia), and determining if variation in the stress response modifies adjustment of rapidly modifiable behavioral components of reproductive effort. Understanding how variation in the stress response mediates plasticity in reproductive effort will elucidate the potential for organisms to cope with both natural perturbation factors and anthropogenic habitat change.

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Approved

Under Project # 21464 | Research

Coping with environmental perturbation: Adaptive plasticity in reproductive effort and mediation by the adrenocortical stress response

graduate_student - University of California, Riverside

Reservation Members(s)

Melissa Grunst May 1 - Jul 31, 2010 (92 days)

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Dorm 1 May 1 - Jul 31, 2010
Q1 1 May 1 - Jul 31, 2010
Q2 1 May 1 - Jul 31, 2010
Q3 1 May 1 - Jul 31, 2010
Q8 1 May 1 - Jul 31, 2010