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A Quantitative Assessment of the Changes in Pleistocene Mammal Distributions in Response to GlaciationEPA Grant Number: U915414
Title: A Quantitative Assessment of the Changes in Pleistocene Mammal Distributions in Response to Glaciation
Investigators: Lyons, S. Kathleen
Institution: University of Illinois at Chicago
EPA Project Officer: Just, Theodore J.
Project Period: October 1, 1998 through September 1, 2001
Project Amount: $100,100
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objective of this research project is to examine the effects of climate change on ecological communities.
If species are shifting their ranges independently, resulting in nonanalogue communities, then a similarity index calculated between a site at time t1 and that same site at time t2 (where t1 is the oldest time period) should not be different from a distribution of similarity indices calculated between a site at t1 and randomly generated assemblages for time t2. Faunal lists of Pleistocene mammals compiled by site locality were gathered from the literature and from the World Wide Web. This information was split into four time periods: preglacial, full glacial, postglacial, and modern. Total area of a species distribution was calculated as the area within a minimum convex polygon that enclosed all the localities for that species. Changes in distributions from one time period to the next (i.e., range shifts) were calculated as the change in area of a distribution, distance the centroid of a species range moved, and the direction the centroid of a species range moved. If a species occurred in one time period and not the next, it was assumed to have shifted its range outside the United States. Range shifts were sampled randomly, and artificial distributions of species were created for t2 by applying these randomly generated shifts to distributions from t1. Species composition of sites was determined by including a species in the faunal list if its randomly created range covered that site. A similarity index between the site at t1 and the site in the randomly created t2 was calculated, and this process was repeated 10,000 times to create a distribution of similarity indices. The actual similarity index was compared to this distribution, and was considered significant if it fell in the tails of the distribution (i.e., upper or lower 2.5 percent). As with any model, it is important to determine the effect of model assumptions on results. In addition to the basic model described above, different model assumptions were altered to determine their effect on the resulting patterns.