Taxonomic and Phylogenetic Homogenization Across US National Parks: The Role of Non-native Species

Abstract

US national parks are firmly engrained into the culture of the country. Since the first national park was established in 1872, these protected areas have been central to biodiversity conservation, education, and recreation in the United States. However, national parks face many of the same threats to biodiversity as non-protected areas, including non-native species invasion. As invasive species spread and replace native species across national parks, the composition, function, and evolutionary history of these ecological communities continue to change. To better understand the impact of non-native species on ecological communities in US national parks, we compared species composition for bird and plant assemblages in 244 and 241 national park units, respectively, with and without non-native species. We specifically ask if the establishment of non-native species has resulted in taxonomic and phylogenetic homogenization across national parks. We show that the establishment of non-native plants in US national parks has resulted in both taxonomic and phylogenetic homogenization. However, the establishment of non-native birds has led to phylogenetic differentiation in spite of taxonomic homogenization, indicating that taxonomic and phylogenetic homogenization are decoupled. As the uniqueness of regional floras and faunas is lost through the process of homogenization, not only is biodiversity lost but so are cultural resources and values that define the United States.