1. Is there a bias in deep sea
diversity patterns?
Graeme T. Lloyd

2. Collaborators
Andrew Jeremy Paul
Smith Young Pearson

3. Talk Outline
• Introduction
• Deep sea diversity patterns:
– Deep sea diversity through time
– Deep sea rock record through time
– Correlations
– Modeling
• Species-per-genus patterns:
– Species-per-genus through time
– Deep sea rock record through time
– Authors through time
– Correlations
– Modeling
• Other diversity curves

4. Introduction

5. Fossil record is our only record of the
diversification of life

6. Diversity correlates with rock record on
land…
Peters and Foote 2001 Smith and McGowan 2007

7. …but what about the deep sea?
• Widely regarded as the best record we have:
– Larger spatial extent than land
– Abundant and widespread taxa
– Near continuous sedimentation
– Well studied (e.g. DSDP/ODP/IODP)

8. The database
• Study group is Coccolithophores
• Novel compilation from North Atlantic
• Compiled from 40 years ODP/DSDP
data
• >50,000 occs from >15000 samples
• High temporal resolution (nanno zones)
Questions:
• What is the deep sea diversity pattern?
• What is the deep sea rock pattern?
• Are the two correlated to any degree?

9. Deep sea species richness

10. Deep sea rock record

11. Correlation tests
• First both time series were log-transformed
• Long term test:
– Simple correlation
• Short term tests:
– First differences (absolute)
– Moving average differences (relative to long
term trend)
• Degree (rho) and significance (p) of
correlations determined using Spearman
rank

12. Deep sea long-term correlation

13. Deep sea short-term correlation I

14. Deep sea short-term correlation II

15. Modeling approach

16. Modeling results
Real data
Predicted

17. Deep sea conclusions
Questions:
• What is the deep sea diversity pattern?
– Linear rise with short-term fluctuations
• What is the deep sea rock pattern?
– Exponential rise with short-term fluctuations
• Are the two correlated to any degree?
– Yes, strongly and significantly, long-term and short-
term
– N sites is a good predictor of species richness

18. Species per genus patterns

19. Higher taxa as species proxies
• Used since the earliest diversity curves…
• …and continue to be (e.g. Alroy et al. 2008)
• Originally pragmatic (less data required)
• Then argued that species are inadequate
• But, adequacy of higher taxa to represent
species-level patterns is essentially untested

20. Taxonomic level affects pattern

21. Flessa and Jablonski 1985
• Only explicit test of
species-to-higher
taxon ratio
• Compared families
to number of named
species in Zoo.
Record (Raup 1976)
• Pattern of change
differs; families
become more
speciose

22. Our database is superior!
• Species are standardised (synonyms)
• Species are assigned to genera
• Species are often widespread
• Species are long-ranging
• Species are comparatively stable
taxonomically
• Question: how does the species-to-genus
ratio change over time?

23. Species per genus

24. Number of sites

25. Number of authors

26. Long-term correlation
N sites
N authors

27. Short-term correlation
Species per genus
N sites

28. Short-term correlation
Species per genus
N authors

29. Correlations and conclusions
• Both number of sites and number of authors
significantly correlate with species-per-genus
• Which is the best explanatory model?
– Akaike weights = a combined model
– Variance partitioning = a combined model
• Genera are not an accurate proxy for species
• Shift in species-per-genus ratio is best explained
by a combination of sampling and worker bias, with
limited room for a biological explanation

30. Other diversity curves

31. Other diversity curves

32. Other diversity curves