What Does the Fossil Record
Show About Recovery?
Brook Milligan
Department of Biology
New Mexico State University
Las Cruces, New Mexico 88003
[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 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?