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

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-CO 2 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 CO 2 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

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

“…Enhanced aeolian supply relative to detrital fluxes into the Neo-Tethys has been reported on the southern Tethyan margin (central Egypt) as a result of drier, likely more seasonal, climatic conditions during the Paleocene-Eocene Thermal Maximum (PETM) (Schulte et al, 2011). Similar observations have been made for the PETM in the Bighorn Basin, Wyoming (Wing et al, 2005;Kraus and Riggins, 2007;Smith et al, 2009), East Africa (Handley et al, 2012) and the southern Kerguelen Plateau, Indian Ocean, on the Antarctic margin .…”

Environmental and scale-dependent evolutionary trends in the body size of crustaceans

“…[14]), dwarfing ('Lilliput effect') following mass extinctions (e.g. [15,16]; but see [17]), changes in body size as a function of niche availability [18], long-term trends driven by climate change (e.g. [19]) and taxon-specific intrinsic constraints [20].…”

Impact of the Paleocene–Eocene Thermal Maximum on the macrobenthic community: Ichnological record from the Zumaia section, northern Spain

“…So far, benthic analysis has been mainly focused on microfossil data, mainly benthic foraminifera and secondarily ostracode assemblages, while the effects of the PETM on macrobenthic environment has been scarcely considered (see recent ichnological analyses in Nicolo, 2008, andSmith et al, 2009). However, biogenic structures reveal trace maker behavior in response to environmental features, providing a valuable information on paleoenvironmental dynamic as well as to approach future environmental changes.…”