Exploring Predator-Prey Interactions in Devonian Strophomenate Brachiopods

  • Author / Creator
    Selles, Claudia M.
  • Predation is an important process that helps to shape community structure. The study of predation in the fossil record has often used repair scars – traces of failed predatory attacks left on prey individuals – to identify differences in predation pressure across space, time, and taxa. However, fossil studies of communities and predation are often conducted at very different scales: paleocommunities may be sampled over millions of years while the effects of predation can be tested within a single bed or assemblage. Here, I used repair scars on brachiopod prey to evaluate: 1) whether predation is detectable as a driver of fine-scale community structure in the fossil record, and 2) which prey and environmental characteristics most strongly influence the likelihood of an individual being repaired over a broad spatio-temporal scale.
    Paleocommunity studies have historically focused on depth and other environmental processes over ecological processes such as predation. This may be due to sampling at large spatio-temporal scales, at which environmental processes overprint finer-scale ecological ones. I directly tested predation and depth as drivers of Late Devonian brachiopod paleocommunities from Iowa over a time interval of ~ 1 My. Ordination of sampled communities revealed that both predation and depth influenced species distribution, but predation was the primary driver.
    Individual characteristics such as prey size, ornament, and latitude have been identified as having an influence on the frequency and outcome of predatory attacks. However, these characteristics have infrequently been evaluated for their relative effect size on predation and only at small scales. Here, I examined Mid- to Late Devonian concavo-convex brachiopods from across North America for repair scars and created generalized linear mixed models including six candidate variables to explain and predict the likelihood of an individual being repaired. I found that prey size, shell convexity, and paleolatitude were most strongly associated with repairs, and the effect of size was greater than that of both convexity and paleolatitude. The effect of each of these variables on the likelihood of repair can be attributed to differences in attack frequency: attacks were more frequent on larger, less convex (flatter) individuals living at lower latitudes. The rate of success may have had an additive effect of attacks on larger prey being less successful, resulting in a greater likelihood of repair for these individuals.
    As a whole, these studies revealed that predation can have a detectable influence on species distribution in the fossil record, and that prey and environmental characteristics – size, convexity, and paleolatitude in particular – can be used to explain and predict the likelihood of prey individuals being repaired.

  • Subjects / Keywords
  • Graduation date
    Spring 2022
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.