EAS Impressions

This segment is to shine a spotlight on graduate and undergraduate research in the Department of Earth and Atmospheric Sciences. This month, we are pleased to present an interview with Eilidh Richards, who published the results of her undergraduate thesis in the international science journal, Palaeogeography, Palaeoclimatology, Palaeoecology. Her supervisor was Dr. Lindsey Leighton, and it is worth noting that publishing undergraduate research is an unusual accomplishment.

Below is a summary of the research written by Eilidh. Her research experience is discussed on the accompanying video.

Examining predation in the fossil record can provide insight into predator-prey relationships and evolutionary processes. An important aspect of evaluating predation is the adaptive gap (the relative effectiveness in abilities) between predators and prey, as a fluctuation between the relative success of predators and prey through time may indicate an evolutionary arms-race. We can observe predatory attacks on shelled marine invertebrates, like brachiopods, in the fossil record. One of the most common examples of predation in the fossil record is repair scars, which occur when brachiopods regrow their shells after surviving a predatory attack, often resulting in distortions in their growth lines, analogous to how tree rings might be distorted by damage. However, because repairs indicate failed predation attempts, their interpretation is ambiguous (an increase in repair percentage may be due to an increase in attacks by the predator or it may be due to a decrease in the success of the predator). To differentiate between these two interpretations, we can use the size refugia approach. We expect the position of the size refuge (the size of the prey at which the predator is unable to take the prey) to change as the adaptive gap between predators and prey changes, which would indicate that the change in repair frequency is related to a change in the success of the predator, as was observed in the studied atrypide brachiopods. If there is no change in the position of the size refuge, there is no change in the relative abilities of predator and prey and thus, the change in repair frequency is related to a change in the number of predatory attacks, as was the case with the studied strophomenide brachiopods. By using the size refugia method, we have found a way of evaluating the adaptive gap accurately; if there is evidence of fluctuations in the gap through time, this may indicate that there is an arms-race occurring between predators and prey.


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