Changing environmental conditions

In endotherms, body size often increases with latitude. This pattern, referred to as Bergmann's Rule, is thought to occur because bigger individuals are better at retaining heat in colder environments, but worse at dissipating heat in warmer environments. A recent extension of this idea is that individuals will shrink in response to rising temperatures. However, the mechanisms that underlie this pattern, including to what degree it is due to plasticity versus evolved responses, are not well understood. This project is examining the mechanisms that mediate rapid shifts in body size and other life-history traits in house sparrows using a combination of historical and newly collected data and samples, a reciprocal transplant experiment, and a hormonal manipulation across a latitudinal gradient. As part of these studies, breeding nest-box populations of house sparrows have been established at two tribal colleges and three additional sites along a latitudinal gradient. This integrative study spans levels of analyses from gene expression to population level variation in life-history traits and will enhance our understanding of the mechanisms that underlie a long standing ecological pattern and mediate rapid phenotypic responses to climate change.