Novelty in space and time: Linking pattern and process to understand the drivers of late-glacial no-analog plant associations
Talk presented at the 2013 International Biogeography Society metting in Miami, USA, in the Paleobiogeography and Historical Biogeography session.
Abstract: The Pleistocene-Holocene transition in North America (17 ka BP to 8 ka BP) was a time of widespread environmental change, including the arrival of humans, the extinction of 35 genera of megaherbivores, and individualistic shifts in species’ ranges and abundances in response to climate change and melting ice sheets. The widespread formation of novel plant associations during this interval is presumed to be the result of novel environmental conditions, but the relative importance of various proposed causal mechanisms remains unclear. We present a synthesis is of 7 well-dated, high-resolution pollen records from new and re-cored classic sites in the Great Lakes region of the Midwest, USA. Dissimilarity analysis indicates that the late-glacial no-analog plant associations were more narrowly constrained in this region (14.5 ka BP to 11.8 ka BP) than reported in previous sub-continental-scale syntheses (17 ka BP to 11 ka BP). A nonmetric multidimensional scaling analysis was conducted to reconstruct the trajectory of the sites in ecological space through time. Results reveal 1) abrupt changes in vegetation and increased variability within and between sites during the no-analog interval, 2) a distinct northwest-southeast time-transgressive pattern, as well as 3) interregional phenomena within the no-analog interval. Between-site differences in the behavior of key pollen types (e.g., Fraxinus nigra-type, Ostrya-type, and Picea) suggest that local site factors may have influenced the individualistic response of taxa to extrinsic abrupt forcing, including megafaunal extinction and climate change, resulting in particular novel plant associations that were unique to the region.