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2009 Portland GSA Annual Meeting (18-21 October 2009)

Paper No. 11
Presentation Time: 10:45 AM

THE PLIO-PLEISTOCENE EXTINCTIONS IN FLORIDA AND THE ECOLOGY OF DUROPHAGOUS PREDATOR-PREY INTERACTIONS


PIETSCH, Carlie, Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Zumberge Hall of Science, Los Angeles, CA 90089, DIETL, Gregory, Paleontological Research Institution, 1259 Trumansburg Road, Ithaca, NY 14850 and HERBERT, Greg, Department of Geology, University of South Florida, 4202 E. Fowler Avenue, SCA 528, Tampa, FL 33620, cpietsch@usc.edu

The Caribbean experienced an ecosystem-wide extinction near the end of the Pliocene. In Florida specifically, there was a 70% extinction of gastropod taxa since the mid-Pliocene. This extinction was selective for species with certain characteristics. For example, hard bottom dwelling gastropods with thick lips and narrow apertures suffered more than species lacking these traits (Vermeij and Petuch, 1986).

Past evidence for reduced intensity of ecological interactions following the extinction has been indirect. Here, we seek direct examination of predatory interactions by quantifying drilling and repair scar frequencies in muricid gastropods of the genera Phyllonotus and Chicoreus. We hypothesize that frequencies of attack and repair have declined since the Pliocene.

Phyllonotus and Chicoreus from four formations bracketing the extinction boundary were measured and then examined for crab repair scars and muricid and octopod drill holes. Predation frequency was calculated for each of these types of predation scars for each individual formation. Significant decreases in confamilial muricid predation occurred during the Pliocene (Phyllonotus: 7.6% decrease in predation frequency, p=.0124) and octopod predation decreased across the Plio-Pleistocene extinction boundary (Phyllonotus: 26.8% decrease, p=.0331; Chicoreus: 10.4% decrease, p=.024). Crab repair scars on the body whorl showed a significant decrease throughout the Pliocene (Phyllonotus: 37.9% decrease, p=.0298). These changes support our hypothesis that there was a decrease in the intensity of predatory interactions in the muricid predator-prey system.

These results also represent evidence for an extensive extinction period from the beginning of the Pliocene into the Pleistocene. Through this study we add to the ecological understanding of this event. Decreases in predation intensity correspond to known changes in oceanic circulation and levels of competition among organisms of the Floridian Plio-Pleistocene habitat.

Session No. 146

Paleontology: Predation & Diet
Tuesday, 20 October 2009: 8:00 AM-12:00 PM
Portland Ballroom 256 (Oregon Convention Center)
Geological Society of America Abstracts with Programs. Vol. 41, No. 7, p.391
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