Downs Lab Research

What’s size got to do with it? The role of body size in host competence

The way a trait changes with body size is termed scaling, and scaling theory posits that body mass constrains organisms’ morphology, physiology, behavior, and life-history traits. We are investigating whether body mass alters the architecture of immune defenses and host competence. In addition to developing a theoretical framework for integrating body size into host competence models, we are leveraging samples banked at zoos across the US to investigate how >150 terrestrial mammals spanning 7 orders magnitude body size control various microbial pathogens. We are also quantifying oxidative stress and recovery in 100 species of birds and mammals, and we are using RNAseq to discern which innate immune genes, gene networks, and/or gene modules are most sensitive to body mass among species of primates.

Main Collaborators: Lynn (Marty) Martin, and Rays Jiang

Assessing the physiological condition and diet of the imperiled New England cottontail in newly-restored early successional forest

To inform forest management strategies for imperiled New England Cottontail, we will use molecular genomics analyses to determine diet and will use fecal glucocorticoid metabolites (FGM) to assess physiological health. We will correlate diet and FGM data with habitat and survival data to determine how habitat use affects survival through these mechanisms.

Main Collaborators: Members of the Wood Rabbit Project

Incorporating energetic costs: the influence of nutritional state and life stage on immune defenses

Individuals use two strategies for coping with parasite infections. Resistance involves controlling the number of parasites by avoiding the infection, killing or removing parasites, or limiting the parasites’ ability to reproduce in the host. Alternatively, tolerance involves minimizing the costs of infection by preventing or repairing the damage caused during infection. But how do individuals decide which strategy to use? Building on life history theory, individuals should invest in the strategy that best improves lifetime fitness. Thus, environmental conditions and life stages that alter nutritional condition should alter the parasite-coping strategy employed. We are currently investigating these ideas in a variety of study systems including golden eagles, mule deer, elk, Dall sheep and mice.

Main Collaborators: Kelley Stewart, Kevin Monteith, and Western Golden Eagle Conservation Team

Trade-offs among physiological and ecological traits in mice

Much research has supported the trade-offs expected by the pace-of-life hypothesis. However, much of this research has focused on observed correlations or within life-time changes of a trait (i.e., changes in gene expression) making it difficult to determine if trade-offs are evolutionarily constrained. Artificial selection experiments allow a researcher to determine how selection on a trait of interest results in correlated evolutionary change in another trait of interest. I have utilized mice from from two selection experiments to test hypotheses about evolutionary trade-offs among physiological and ecological traits such as growth rate, immune function, activity, basal and maximal metabolic rates, and body composition.

Main Collaborators: Jack Hayes, Ted Garland, Bernie Wone, and Heidi Schutz