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Leighton & Sawyer - Predator-Prey Dynamics of Late Paleozoic Ecosystems: A Case-Study on the Role of Molluscs

Predator-Prey Dynamics of Late Paleozoic Ecosystems:
A Case-Study on the Role of Molluscs

Lindsey R. Leighton and Jennifer A. Sawyer

Department of Geological Sciences &Allison Center for Marine Research

San Diego State University, San Diego, CA, 92182-1020

leighton@geology.sdsu.edu

Predation plays a major role in modern molluscan ecology but knowledge of the origins of molluscan predator-prey dynamics in deep time remains limited. The majority of Early Paleozoic gastropods and bivalves were restricted to nearshore habitats but during the Carboniferous both classes radiated into ânormalâ marine systems, at which time molluscs were exposed to a greater risk of predation. Previously, predators primarily attacked brachiopods. How did the molluscan invasion of these ecosystems affect predator-prey dynamics and did molluscs respond to this increase in predation? We examine several exceptionally well-preserved assemblages from the Late Carboniferous of Texas that include diverse gastropods, bivalves, and brachiopods, especially pleurotomariniid gastropods; mobile, shallow-infaunal, bivalves; and productide brachiopods. Most taxa are similar in size and shell thickness, so predators might be expected to prefer fleshier molluscs over brachiopods. Drilling predation was restricted entirely to sedentary, epifaunal taxa, regardless of taxonomic affinity; these drillers apparently were not as adept as some Recent drillers at capturing mobile prey. Crushing predators, however, left scars on gastropods (18% of specimens) much more frequently than bivalves or brachiopods (8% each; difference is significant: chi-square test, p < 0.01). This difference is either due to a greater rate of attacks on gastropods or greater success against other taxa. Bivalve crushing frequency may be low because most bivalves were infaunal. The higher frequency of scars on gastropods suggests that an increase in ornament in many gastropods lineages, including the abundant pleurotomariniids, during the Late Carboniferous, may have been an adaptive response to predation.


next up previous
Next: Lockwood - Extinction and Up: Special Symposium - From Previous: Hadfield & Koehl -
Peter Roopnarine 2005-04-12