Graeme T. Lloyd, Andrew B. Smith and Jeremy R. YoungDepartment of Palaeontology,The Natural History Museum, London, UK

Different records give different curves: comparing deep sea and land-based

palaeobiodiversity

Sedimentary record

Habitat availability

Samplingopportunity

Raw palaeodiversity

Geotectonic history

Macrostratigraphic record

Biological driverRock record driver

Sedimentary record

Habitat availability

Samplingopportunity

Geotectonic history

Macrostratigraphic record

Biological driverRock record driver

Rock bias hypothesis

Raw palaeodiversity

Sedimentary record

Habitat availability

Samplingopportunity

Geotectonic history

Macrostratigraphic record

Biological driverRock record driver

Common cause hypothesis

Raw palaeodiversity

Raw palaeodiversityMacrostratigraphic record

Which pathway drives the fossil record?Problem so far is that we have been looking at how different taxonomic groups are affected in the same rock record - where both rock and fossil records are created by the same

set of drivers

To understand which pathway drives the fossil record

We need to look how the evolutionary history of a single widespread marine group (coccolithophorids)

is recorded by 2 contrasting rock records(deep sea v. land based)

Deep sea Land

coccolithophorids

Predictions

Deep sea Land

coccolithophorids

Common cause - correlation between sampled diversity and rock record in only one of the environments (land)

Rock record bias - both environments will show strong link between sampled diversity and rock record

205 sites, 14405 samples,46538 occurrence records

462 sections, 5563+ samples,22745 occurrence records

Deep sea Land

Databases

Time (Ma)

Number of cores recovering rock of given age

Rock record

Deep sea Land

Rock records

Number of localities with published nannofossil taxonomic lists

Time (Ma)

Time (Ma) Time (Ma)

Number of species

Raw species diversity

Number of species

Deep sea Land

Species diversity in fossil records

Deep sea Land

Log (Nsites)

Log (species richness) Log (species richness)

Log (Nsites)

Species diversity versus rock record (1): raw data

Deep sea Land

Log (species richness) Log (species richness)

Log (Nsites) Log (Nsites)

Species diversity versus rock record (1): first differences

Deep sea Land

Two diversity curves - so which (if either) is correct?

Use 4 techniques to try to find the true underlying diversity:• Rarefaction• Modeling• Alpha diversity estimates• Shareholder quorum

With two rock records can cross-validate methods!

Estimating True Diversity

Deep sea Land

Blue = empirical patternBlack = diversity at equal subsampling

Time (Ma)

109 samples per bin

Time (Ma)

Species diversity (max) Species diversity (max)

106 samples per bin

Estimating True Diversity: 1, Rarefaction

Blue = empirical patternRed = model prediction assuming diversity is invariant

and shaped by rock abundance

Time (Ma) Time (Ma)

Species diversity Species diversity

Diversity modeled as invariant

Deep sea Land

Estimating True Diversity: 2, Modeling

Deep sea Land

Time (Ma)

Residuals from modeled diversity

Time (Ma)

Estimating True Diversity: 2, Modeling

Time (Ma)

Deep sea Land

Species

Time (Ma)

Species

Time (Ma)

Estimating True Diversity: 3, Alpha Diversity

Mean number of species recorded per site

Deep sea Land

Species

Time (Ma)

Species

Time (Ma)

Estimating True Diversity: 4, Shareholder Quorum

Shareholder quorumrichness at q = .40

• The recorded history of coccolithophorid diversity over last 150 Ma changes dramatically according to whether data is drawn from land-based or deep-sea rock records

• Coccolithophorid diversity correlates strongly to the shape of the rock record it is recovered from

• Subsampling, modeling and estimates of mean alpha diversity all point to a third, much more uniform, diversity over time irrespective of which record is used

Deep sea Land

Summary

Predictions

Deep sea Land

coccolithophorids

Common cause - little or no correlation between diversity and rock record in the deep sea

Rock record bias - both environments will show strong link between diversity and rock record

Sedimentary record

Habitat availability

Samplingopportunity

Palaeodiversity

Geotectonic history

Macrostratigraphic record

Biological driverRock record driver

Rock bias dominates