What Does the Fossil Record Show About Recovery? Brook Milligan Department of Biology New Mexico State University Las Cruces, New Mexico 88003 brook@nmsu.edu Fall 2009 Brook Milligan What Does the Fossil Record Show About Recovery?
What are the questions? How does biodiversity recover from extinctions? Is it rapid enough to keep pace with extinctins? Is there a significant lag between extinctions and recovery? Does extinction create empty niches that can be rapidly filled by new species? Does recovery increase the rate of recovery? Is recovery different for background and mass extinctions? Does the answer depend on how recovery is measured? Brook Milligan What Does the Fossil Record Show About Recovery?
How can they be answered? Must know: temporal sequence of extinctions temporal sequence of origination Need: quantified relationship between extinction and recovery Difficulties both extinction and recovery have a significant stochastic component Brook Milligan What Does the Fossil Record Show About Recovery?
Two approaches Cross-correlation Spectral analysis Brook Milligan What Does the Fossil Record Show About Recovery?
Cross-correlation: Methods Calculate cross-correlation between extinction and origination Identify significant cross-correlations Determine phase shift Brook Milligan What Does the Fossil Record Show About Recovery?
Fossil Record: Diversity, Extinction, Origination Brook Milligan What Does the Fossil Record Show About Recovery?
Fossil Record: Cross-correlation Brook Milligan What Does the Fossil Record Show About Recovery?
Fossil Record: Expectations from Distortions Brook Milligan What Does the Fossil Record Show About Recovery?
Cross-correlation: Results 10 MY lag from extinction to origination Lag does not depend greatly on: means of quantifying extinction/origination presence/absence of mass extinctions completeness of fossil record Brook Milligan What Does the Fossil Record Show About Recovery?
Spectral analysis: Methods Transform time series into spectral domain Identify frequencies beyond confidence intervals Brook Milligan What Does the Fossil Record Show About Recovery?
Fossil Record: Diversity, Extinction, Origination Brook Milligan What Does the Fossil Record Show About Recovery?
Spectral Analysis Brook Milligan What Does the Fossil Record Show About Recovery?
Spectral Analysis Brook Milligan What Does the Fossil Record Show About Recovery?
Fossil Record: Rates of Extinction and Origination Brook Milligan What Does the Fossil Record Show About Recovery?
Spectral analysis: Results Extinction: all frequencies within confidence interval Origination: only short wavelength frequencies significantly reduced Rapid response for origination lacking Brook Milligan What Does the Fossil Record Show About Recovery?
Implications Significant lag between extinction and recovery Lag present for all types of extinction events Recovery cannot occur rapidly Current human impacts will leave a signature on biodiversity for millions of years Brook Milligan What Does the Fossil Record Show About Recovery?
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