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
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?
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
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
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
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?
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