Human Land Use Impacts on Native Plant Genetic Diversity

Abstract

Extensive research has been conducted to determine how urbanization and human land use affect the genetic diversity and population structure of animal populations. Plant populations experience many direct and indirect effects of human activities, such as habitat fragmentation, the introduction of invasive species and herbivores, and declines in pollinators. Despite awareness that urbanization and agriculture are the largest threats to plants globally, very little research has directly assessed this relationship on a broad scale. To examine this, I compiled a list of 2745 terrestrial plant species endemic to North America from the IUCN and then conducted a programmatic search of the Dryad Digital Repository for microsatellite genetic datasets for these species. Upon manual review of these datasets, 15 appropriate datasets with georeferencing were selected for usage in this study. The final database comprised 7535 individuals of 427 populations of 21 species. I estimated gene diversity, rarefied allelic richness, and population-specific FST for each site and used these values as response variables in a series of Bayesian Hierarchical Generalized Linear Mixed Models (GLMMs) to test relationships between population genetic composition and human land use. I treated species as a random effect with random slopes and intercepts. This allowed me to observe species-specific trends in the data. My results indicated that across 21 species, populations in areas with high rates of human land use exhibit greater population differentiation and higher overall genetic diversity. In contrast, areas with high human population density showed overall increases in genetic diversity and decreased population differentiation. My results show clear, albeit weak, trends, suggesting that the small sample size and lack of diversity in life history traits were limitations.