The effect of geographic range on extinction risk during background and mass extinction
- Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305
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Edited by Steven M. Stanley, University of Hawaii at Manoa, Honolulu, HI, and approved April 26, 2007 (received for review February 9, 2007)
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Fig. 1.Phanerozoic trends in the geographic range selectivity of genus survivorship. Log-odds of zero indicate no association, positive log-odds indicate a positive association between geographic range and extinction risk, and negative log-odds indicate an inverse association. Note that selectivity is least pronounced at times of major extinction events (indicated with arrows) but generally indicates a positive and significant association between geographic range and survivorship. (A) Selectivity estimated from a single logistic regression of geographic range versus survivorship. (B) Geographic range selectivity from multiple logistic regression of geographic range, species richness, and occurrence frequency versus survivorship. Gray lines are 95% confidence intervals on estimated odds ratios. Logarithmic vertical axes are used to preserve symmetry. Pz, Paleozoic; Mz, Mesozoic; Cz, Cenozoic; Cam., Cambrian; Ord., Ordovician; Sil., Silurian; Dev., Devonian; Carb., Carboniferous; Perm., Permian; Trias., Triassic; Jur., Jurassic; Cret., Cretaceous; Pg., Paleogene; N., Neogene. Major extinction events are indicated by arrows: LOr, Late Ordovician; Fra, Frasnian; Fam, Fammenian; PT, P–T; TJ, T–J; KT, K–T. Estimates are less stable in the multiple regression (i.e., 95% confidence intervals are broader) because the three examined variables are collinear.
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Fig. 2.Geographic range selectivity versus extinction intensity. Note that extinction intensity is generally high in the Cambrian–Ordovician and low in the Mesozoic and Cenozoic. Selectivity exhibits a weak inverse association with extinction intensity, which is discussed in the text. Log-odds are from the single regression of geographic range. Abbreviations are as in Fig. 1.
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Fig. 3.Observed geographic range selectivity versus expected selectivity measured as log-odds if extinctions were entirely independent across plates. Intervals with less-than-expected geographic range selectivity are disproportionately intervals associated with geological evidence for widespread environmental disturbance. Geographic range selectivity values are from the univariate analysis. Abbreviations and symbols are as in Fig. 2. Cen, Cenomanian; Giv, Givetian; Guad, Guadalupian; Pli, Pliensbachian–Toarcian; Tur, Turonian–Santonian; ETr, Early Triassic.
Footnotes
- †To whom correspondence should be addressed. E-mail: jlpayne{at}stanford.edu
- © 2007 by The National Academy of Sciences of the USA
