What Does the Fossil RecordShow About Recovery?
Brook Milligan
Department of BiologyNew Mexico State University
Las Cruces, New Mexico [email protected]
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 filledby 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 extinctionstemporal sequence of origination
Need:
quantified relationship between extinction and recovery
Difficulties
both extinction and recovery have a significant stochasticcomponent
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/originationpresence/absence of mass extinctionscompleteness 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 significantlyreduced
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 biodiversityfor millions of years
Brook Milligan What Does the Fossil Record Show About Recovery?
