Meeting Abstract
The population dynamics of snowshoe hares (Lepus americanus) are fundamental to the ecosystem dynamics of Canada’s 5,000,000 km2 boreal forest. Their 8-11 year population cycle is driven by predation, and hare densities can fluctuate up to 40-fold over the cycle. Predators (lynx, coyotes, great-horned owls) affect population numbers not only via direct mortality, but also through the indirect effects of chronic stress. Hares severely stressed by the threat of predation have been found to have greater plasma cortisol and glucose levels at capture and in response to hormonal challenge, heightened ability to mobilize cortisol and energy, and a poorer body condition. These effects may result in, or be mediated by differential gene expression. We tested transcriptional responses in the brain to elevated predation risk. An oligonucleotide microarray designed for a closely related species, the European rabbit, was used to characterize differences in hippocampal transcript abundance between wild-caught males during years of low versus high predator risk. A total of 106 gene loci were identified as having significant differences in transcript abundance between years. Results for candidate genes were validated with quantitative real-time polymerase chain reaction, and orthologous protein sequences were used for functional enrichment analysis of gene sets. Hares exposed to high levels of predation risk showed increased activity of genes involved in metabolic processes and hormone response, and decreased activity of genes involved in blood cell formation and immune response. These results are concordant with the physiological changes measured in previous studies. They indicate that there are pronounced transcriptional changes in the brain that occur in synchrony with changes in predation risk.
