Nanismo transitório da fauna de solo durante a temperatura máxima no Paleoceno-Eoceno

Transient dwarfism of soil fauna during the Paleocene–Eocene Thermal Maximum

Jon J. Smith a,b,1, Stephen T. Hasiotis b, Mary J. Kraus c and Daniel T. Woody c

+ Author Affiliations

aKansas Geological Survey, University of Kansas, 1930 Constant Avenue, Lawrence, KS 66047-3724;

bDepartment of Geology, University of Kansas, 120 Lindley Hall, Lawrence, KS 66045-7613; and

cDepartment of Geological Sciences, University of Colorado, 2200 Colorado Avenue, Boulder, CO 80309-0399

Communicated by Thomas N. Taylor, University of Kansas, Lawrence, KS, August 24, 2009 (received for review May 1, 2009)

Abstract

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene–Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30–46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO2 atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO2 and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.

climate change evolution extinction ichnofossils paleosols

Footnotes

1To whom correspondence should be addressed. E-mail: jjsmith@ku.edu

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

The authors declare no conflict of interest.

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