EFFECTS OF DRILLING PREDATION ON GLOBAL TURRITELLID DIVERSITY AND ABUNDANCE: A POTENTIAL CATALYST FOR EVOLUTION

Predation is considered by some to be a major agent of natural selection, and therefore testing hypotheses about how organisms respond evolutionarily to stresses from predators is critical for understanding the vehicles of evolution. The fossil record of drilling predation has been used extensively to infer predator-prey relationships and to test hypotheses about evolutionary paleoecology. Of primary concern is how drilling predation affects species diversity, as it can potentially affect both speciation rate and extinction rate.

A previous study by Kelley et al. (2005) suggests that diversity inversely tracks drilling predation through time; predation apparently caused a decrease in diversity, either by increasing extinction or suppressing speciation. In that study, U.S. Coastal Plain drilling frequency was used as a proxy for global drilling frequencies in correlating drilling with global species diversity. However, it is not clear whether Coastal Plain drilling frequencies are representative of those occurring elsewhere.

Bulk samples from Austria, Italy, Northern Adriatic Sea localities, and the Red Sea containing turritelline gastropods were examined to gain a better idea of global drilling frequencies to compare with global species diversity. More than 2910 specimens from eight middle Miocene to Recent formations were examined for data on turritelline prey drilling frequency, and diversity and abundance. Drilling frequencies as high as 77 percent were found for the Recent samples from the Adriatic, and the older material had significantly lower drilling frequencies of 10 to 18 percent. Most samples had low turritelline gastropod diversity. Frequency data of naticid (predator) drilling on turritellines (favored prey) will be analyzed for statistical relationships and compared to results from previous studies conducted on bulk samples from the United States Gulf and Coastal Plain. Though still in progress, the results of this study will help to understand the global effects of biotic interaction on extinction, speciation, and ultimately, evolution.