Testing the Role of Predation in Morphological Evolution of Marine Prey

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Predation, the act of an organism killing another for food, is believed to influence the evolution and diversity (the number) of species greatly. We currently are experiencing a biodiversity crisis (70 species go extinct per day) so understanding the factors that influence diversity and evolution is vital. There is a hypothesis of “escalation”, which suggests that the main reason why most animals evolve is to defend themselves better from their predators. The fossil record provides a long-term natural laboratory to examine such hypotheses. However, predation is hard to estimate because direct observations of the past are impossible. Thus, we need a means of estimating predation without direct observations. One solution is to use traces of predation, such as scars on the shells of marine invertebrate prey, to estimate the frequency of predation. For example, crabs regularly feed on clams by using their powerful claws to fracture the shell. If the attack fails, then the clam regrows its shell, which now has a repair scar; we can see such scars on fossils.