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What Does the Fossil RecordShow About Recovery?

Brook Milligan

Department of BiologyNew Mexico State University

Las Cruces, New Mexico 88003brook@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 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?

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