title: The impact of Cenozoic cooling on assemblage diversity in planktonic foraminifera.
abstract: The Cenozoic planktonic foraminifera (PF) (calcareous zooplankton) have arguably the most detailed fossil record of any group. The quality of this record allows models of environmental controls on macroecology, developed for Recent assemblages, to be tested on intervals with profoundly different climatic conditions. These analyses shed light on the role of long-term global cooling in establishing the modern latitudinal diversity gradient (LDG)--one of the most powerful generalizations in biogeography and macroecology. Here, we test the transferability of environment-diversity models developed for modern PF assemblages to the Eocene epoch (approx. 56-34 Ma), a time of pronounced global warmth. Environmental variables from global climate models are combined with Recent environment-diversity models to predict Eocene richness gradients, which are then compared with observed patterns. The results indicate the modern LDG--lower richness towards the poles--developed through the Eocene. Three possible causes are suggested for the mismatch between statistical model predictions and data in the Early Eocene: the environmental estimates are inaccurate, the statistical model misses a relevant variable, or the intercorrelations among facets of diversity--e.g. richness, evenness, functional diversity--have changed over geological time. By the Late Eocene, environment-diversity relationships were much more similar to those found today.
authors.affiliation: Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, UK isabel.fenton@nhm.ac.uk.
authors.forename: Isabel S
authors.identifier: http://orcid.org/0000-0001-7174-0725
authors.initials: IS
authors.lastname: Fenton
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, UK.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Pearson
authors.affiliation: School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Dunkley Jones
authors.affiliation: School of Geographical Sciences and Cabot Institute, University of Bristol, Bristol BS8 1SS, UK.
authors.forename: Alexander
authors.initials: A
authors.lastname: Farnsworth
authors.affiliation: School of Geographical Sciences and Cabot Institute, University of Bristol, Bristol BS8 1SS, UK.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Lunt
authors.affiliation: Getech Group plc. Elmete Hall, Elmete Lane, Leeds LS8 2LJ, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Markwick
authors.affiliation: Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, UK.
authors.forename: Andy
authors.initials: A
authors.lastname: Purvis
mesh_terms: D044822:Biodiversity; D005075:Biological Evolution; D057231:Climate Change; D056908:Foraminifera / Q000145:classification*; D005580:Fossils; D010933:Plankton / Q000145:classification*; D013997:Time Factors
keywords: Eocene; global climate model; latitudinal diversity gradient; planktonic foraminifera