Climatically driven macroevolutionary patterns in the size of marine diatoms over the Cenozoic

^*Institute of Marine and Coastal Sciences, Rutgers, The State University of New Jersey, 71 Dudley Road, New Brunswick, NJ 08901; and ^‡Department of Geological Sciences, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854

Edited by Andrew H. Knoll, Harvard University, Cambridge, MA, and approved May 6, 2005 (received for review December 31, 2004)

Abstract

Numerous taxonomic groups exhibit an evolutionary trajectory in cell or body size. The size structure of marine phytoplankton communities strongly affects food web structure and organic carbon export into the ocean interior, yet macroevolutionary patterns in the size structure of phytoplankton communities have not been previously investigated. We constructed a database of the size of the silica frustule of the dominant fossilized marine planktonic diatom species over the Cenozoic. We found that the minimum and maximum sizes of the diatom frustule have expanded in concert with increasing species diversity. In contrast, the mean area of the diatom frustule is highly correlated with oceanic temperature gradients inferred from the δ¹⁸O of foraminiferal calcite, consistent with the hypothesis that climatically induced changes in oceanic mixing have altered nutrient availability in the euphotic zone and driven macroevolutionary shifts in the size of marine pelagic diatoms through the Cenozoic.

Footnotes

↵ † To whom correspondence should be sent at the present address: Environmental Sciences Program, Mount Allison University, Sackville, NB, Canada E4L 1E6. E-mail: zfinkel{at}mta.ca.
Author contributions: Z.V.F., O.M.E.S., and P.G.F. designed research; Z.V.F., M.E.K., and J.D.W. performed research; Z.V.F. contributed new reagents/analytic tools; Z.V.F., M.E.K., P.G.F., and J.D.W. analyzed data; and Z.V.F. wrote the paper.
This paper was submitted directly (Track II) to the PNAS office.