Para sobreviver a extinção em massa: conectar a divisão bêntica com o que mesmo?

Surviving mass extinction by bridging the benthic/planktic divide

Kate F. Darlinga,1, Ellen Thomasb,c, Simone A. Kasemanna,d, Heidi A. Seearse, Christopher W. Smartf and Christopher M. Wadee

+Author Affiliations

aSchool of GeoSciences and Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JW, United Kingdom;

bDepartment of Geology and Geophysics, Yale University, New Haven, CT 06520-8109;

cDepartment of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459;

dInstitut für Geologische Wissenschaften, Fachrichtung Geologie, Freie Universität Berlin, Malteserstrasse 74-100, 12249 Berlin, Germany;

eInstitute of Genetics, University of Nottingham, Nottingham NG7 2UH, United Kingdom; and

fSchool of Earth, Ocean and Environmental Sciences, University of Plymouth, Plymouth PL4 8AA, United Kingdom

Edited by Karl K. Turekian, Yale University, New Haven, CT, and approved May 22, 2009 (received for review April 6, 2009)

Abstract

Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade. For foraminifera, this evolutionary expansion occurred in the Early–Middle Jurassic, and all living and extinct planktic foraminifera have been placed within 1 clade, the Suborder Globigerinina. The subsequent radiation of planktic foraminifera in the Jurassic and Cretaceous resulted in highly diverse assemblages, which suffered mass extinction at the end of the Cretaceous, leaving an impoverished assemblage dominated by microperforate triserial and biserial forms. The few survivor species radiated to form diverse assemblages once again in the Cenozoic. There have, however, long been doubts regarding the monophyletic origin of planktic foraminifera. We present surprising but conclusive genetic evidence that the Recent biserial planktic Streptochilus globigerus belongs to the same biological species as the benthic Bolivina variabilis, and geochemical evidence that this ecologically flexible species actively grows within the open-ocean surface waters, thus occupying both planktic and benthic domains. Such a lifestyle (tychopelagic) had not been recognized as adapted by foraminifera. Tychopelagic are endowed with great ecological advantage, enabling rapid recolonization of the extinction-susceptible pelagic domain from the benthos. We argue that the existence of such forms must be considered in resolving foraminiferal phylogeny.

end-Cretaceous foraminifera Mg/Ca plankton evolution SSU rRNA

Footnotes

1To whom correspondence should be addressed. E-mail: kate.darling@ed.ac.uk

Author contributions: K.F.D. designed research; K.F.D., S.A.K., and H.A.S. performed research; K.F.D., S.A.K., H.A.S., and C.M.W. analyzed data; and K.F.D., E.T., S.A.K., H.A.S., C.W.S., and C.M.W. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

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