In many organisms, body size increases with latitude. This pattern occurs because larger individuals are better at retaining heat in cold environments, but worse at dissipating heat in warm environments. This idea predicts that organisms will get smaller in response to rising temperatures. Although many organisms fit this pattern, the underlying physiology and contribution of genetic changes or environmental conditions is poorly understood. The research will examine the role hormones play in rapidly changing body size in house sparrows. As part of these studies, breeding nest-box populations of house sparrows will be established at two tribal colleges and three additional sites along a latitudinal gradient. An important goal of the study is to provide Research Experience for Undergraduate (REU) opportunities for American Indian students at tribal colleges. Students that participate in REUs experience numerous benefits including increased problem solving skills and enhanced retention in STEM disciplines. However, typical REUs require undergraduates to relocate for extended periods of time, which often conflicts with other family and community commitments. The study seeks to overcome this barrier by creating local REU opportunities at tribal colleges, which will be assessed to inform future educators interested in using similar approaches. In addition, house sparrows will be re-sampled at sites throughout the U.S. and a tissue bank will be created and both historical and contemporary datasets will be published to serve as a permanent benchmark for future studies.
Hormonal mechanisms commonly influence suites of traits and are expected to play an important role in shaping life-history strategies in response to environmental change. The research will test the hypothesis that variation in the insulin/insulin-like signaling hormonal network is a mechanism that mediates rapid shifts in body size along a latitudinal gradient in house sparrows using a combination of historical and newly collected data and samples, a reciprocal transplant experiment, a hormonal manipulation, and transcriptomics. The research will greatly extend what is known about the role of hormonal mechanisms in mediating rapid phenotypic variation in life history traits. Knowledge of how micro-evolutionary and plastic responses contribute to variation in hormonally mediated life history strategies is essential for predicting long-term evolutionary responses to environmental change. If among population variation in hormonally mediated traits is primarily due to micro-evolutionary changes in hormone levels, this is expected to facilitate the rapid evolution of a suite of traits sensitive to the ligand, but to simultaneously limit the independent evolution of these traits. Alternatively, if population level variation is primarily due to micro-evolutionary changes in trait specific receptor densities, traits may evolve independently. If instead, most of the variation is due to developmental plasticity, long-term responses are expected to be more limited. This integrative study spans levels of analyses from gene expression to population level variation in life-history traits and in doing so will enhance our understanding of the mechanisms that underlie a long standing ecological pattern.
This project is jointly funded by the Integrative Ecological Physiology Program and the Established Program to Stimulate Competitive Research (EPSCoR).
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
