Today, 3% of the world's total land cover is considered urban. By 2050, this number is expected to increase to 5%. Urbanization is one of the most significant forms of habitat change, resulting in biodiversity loss through local extinction processes. Urban expansion is expected to impact 25% of all endangered species in the next decade. The overall objective of this project is to investigate how some animals are able to thrive in urban environments while others are not, with a particular focus on how the natural stress response of some birds allows them to respond to factors such as light, noise, and pollution. This stress response differs between individuals that live in urban versus rural areas. This project will determine whether the stress response is genetically inherited by studying house sparrows living in a range of urban and urban settings. There is increasing global effort to build more environmentally-friendly cities, which may reduce stress levels of humans living in densely populated areas. Basic knowledge on how individuals adapt to city life can guide such strategies. The PI will visit a laboratory at Princeton University to learn the genetic techniques required for this project. Increasing her competence in modern molecular genetics through cooperation with Princeton will both establish an important new collaboration, and will significantly contribute to development of her career at the University of Nevada at Reno. In addition, a number of outreach activities are planned, such as the involvement of citizen scientists who will learn about the research process through collection of data from urban nest box studies.
Urbanization affects biological systems worldwide. Phenotypic differences between urban and rural populations demonstrate that some individuals have adapted to city life while others are displaced. A key trait facilitating adaptation is the degree to which animals respond to stress. This stress response has a heritable component and exhibits intra-individual plasticity. However, the mechanisms behind this variability and whether they might be responsible for adaptation to different environments are not known. The overarching hypothesis guiding this work is that an epigenetic mechanism, specifically DNA methylation, is responsible for modifying an individual?s stress response to environmental pressures. Variation in DNA methylation is a prime candidate to explain how organisms adapt to urban environments. Using house sparrows (Passer domesticus) from a gradient of urbanized habitats, the PI will first examine urban-rural differences in DNA methylation patterns at specific candidate genes and relate these patterns to the stress response. To unravel if differences in the stress response are due to heritable adaptation or phenotypic plasticity, an unprecedented cross-fostering field experiment will be integrated with multi-generational screening of the stress phenotype and methylation patterns. This experiment disentangles the contribution of genes, expression, and environmental effects across generations to variation in the stress response. By linking the fields of urban ecology, endocrinology, and epigenetics, this project will pioneer insights into the epigenetic variation underlying a physiological response. Knowledge of the mechanisms behind observed phenotypic differences will enable us to better assess the potential for adaptation of animals to city life, and thereby the impact of urbanization on wild populations. The information acquired is becoming essential in a world that is increasingly experiencing the stress of urbanization.
