550 MILLION YEARS OF DRILLING PREDATION: INITIAL RESULTS FROM A SPECIES-LEVEL PREDATION DATABASE

We constructed a database documenting the occurrence of traces of predation on marine invertebrate prey from the Ediacaran through the Holocene. Previous studies have typically focused on long term trends at low taxonomic resolution (i.e. drilling frequencies of phyla or classes across the Phanerozoic) while others focused on higher resolution taxonomic data at much shorter time scales (i.e., drilling frequencies of families or genera through the Cenozoic). We utilized the published literature (196 papers) to produce a species-level (2291 species occurrences) database on the occurrence of predation-induced traces covering the last 550 million years. Here we report the initial results of the history of drilling predation for species represented by more than ten individuals.

Drilling predation intensity, as suggested by other studies, increased episodically through time. Maximum drilling frequencies for Ediacaran through Silurian species are 10-20%. Maximum drilling frequencies for Devonian-Mississippian species increase to 30-50%. There is a dearth of species-level drilling data in the literature from the Permian through the Triassic. Maximum drilling frequencies increased monotonically from the Jurassic (~30%) through the Quaternary (100%). There is no increase in the lowest drilling frequencies through time; therefore this trend of increasing predation intensity through time is not a directed trend. Indeed it appears to be a passive diffusion from a bounding wall (though trends of increasing as well as decreasing predation intensity within lineages could be obscured within the larger view of the data). Moreover, the pattern exhibited by predation traces (drilling frequency and repair scar frequency) through time closely matches that shown by Sepkoski's genus-level diversity curve. If Sepkoski's diversity curve reflects a true biologic signal, as new species evolved the world became a more dangerous place and predation intensity increased through time. Such a result would lend support to the hypothesis of escalation. However, if the diversity curve is primarily an artifact of biased sampling then perhaps the same goes for the pattern of increasing predation intensity through time.