Evolutionary responses of plants to urban environments

Abstract

Environments in cities are distinctly different from those in rural and natural environments in which plants have, until recently, evolved. As human population migrates to urban centers, and cities develop faster and larger, these environments have the potential to affect plant evolution. The goal of this research was to characterize phenotypic differences in plant populations found in cities compared to those in neighboring rural areas, to identify parallel evolution, and to evaluate the effect of abiotic factors on phenotypic divergence. In Chapter 1, I characterize phenotypic divergence between urban and rural populations of three species, and find that one of these three species is locally adapted. Because cities are characterized by coarsely similar environments, in Chapter 2, I evaluated whether plants found in other cities respond to urbanization in the same patterns, i.e. is there an urban phenotype? Phenotypic data indicate that populations have undergone parallel evolution, but molecular responses are not as straightforward. Finally, in Chapter 3, I test that effect of elevated nighttime temperature and salt stress on phenotypic divergence. I identified that each of these abiotic factors affect plant growth and has the potential to drive phenotypic divergence. Cities are a large and growing proportion of the landscape, therefore, characterizing plant ecology in urban environments provides insight into plant responses to warm and highly altered environments, which are similar to predicted future environments. Thus these data can inform conservation efforts in urban environments in the face of ongoing climate change. This study was also utilized as a model to teach students about evolution and experimental design, and involved high school and college students in ongoing research