Reconstructing 150,000 years of North American plant diversity shifts in response to Late-Quaternary glacial-interglacial cycles

Keywords: Pollen, Climate Change, Plant Diversity, Plants, Vegetation, North America, Functional Traits, Functional Diversity
Abstract Type: Poster Abstract

Abstract

We compiled Late-Quaternary pollen records from North America, ranging from the Yucatán Peninsula through the Arctic to determine shifts in plant diversity over the last ~150 ka. Using Hill numbers, we calculated taxonomic and functional diversity to visualize changes in plant diversity from Marine Isotope Stages (MIS) 5 through 1. We used three levels of taxonomic and functional Hill numbers, q=0, 1, and 2, equivalent to species richness, Shannon index (diversity of species), and Simpson index (relative abundance of species present) for taxonomic and functional attribute diversity (sum of all functional distances) and weighted Gini-Simpson index (relative abundance and functional distance of species present) for the functional q=0 and 2 with no direct analog for q=1. Pollen records were available for several North American ecoregions, covering the Arctic, Pacific Northwest, Intermountain West, Great Lakes, Southeast, Mexico, and Yucatán. We found taxonomic and functional q=0 trends to be distinct from q=1 and 2 while q=1 and 2 share similar shifts in diversity. Regions vary independently of one another in overall trends. In all three levels, functional diversity follows the overall pattern of taxonomic diversity, with shorter periods of mismatch in which trends differ. Areas with high biodiversity currently show high degrees of change, while those with low biodiversity remained stable. Most regional shifts in diversity do not align with shifts in the global temperature record. More work is necessary to refine the regional diversity shifts but our work indicates functional diversity is a valid alternative where taxonomic resolution is lacking.