University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School January 2012 No Honor Among Snails: Conspecific Competition Leads to Incomplete Drill Holes in the Naticid Gastropod Neverita delessertiana (R cluz) Jack A. Hutchings University of South Florida, [email protected] Follow this and additional works at: http://scholarcommons.usf.edu/etd Part of the Other Ecology and Evolutionary Biology Commons Scholar Commons Citation Hutchings, Jack A., "No Honor Among Snails: Conspecific ompeC tition Leads to Incomplete Drill Holes in the Naticid Gastropod Neverita delessertiana (R cluz)" (2012). Graduate Theses and Dissertations. http://scholarcommons.usf.edu/etd/4336 This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. No Honor Among Snails: Conspecific Competition Leads to Incomplete Drill Holes in the Naticid Gastropod Neverita delessertiana (Récluz) by Jack A. Hutchings A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Geology College of Arts and Sciences University of South Florida Major Professor: Gregory Herbert, Ph.D. Peter Harries, Ph.D. H.L. Vacher, Ph.D. Date of Approval: November, 16, 2012 Keywords: Prey Effectiveness, Failure, Predation, Experimental, Ecology Copyright © 2012, Jack A. Hutchings Acknowledgments I am thankful to all those involved in my research and life during the completion of my thesis. My wife, Angela, has been a constant source of support throughout this time. She has been ever willing to listen to my ponderings and problems about snails and clams and life. The faculty of the Geology Department at USF, particularly Gregory Herbert and Peter Harries, were incredibly encouraging to my involvement in geology and paleontology, despite the fact that I came to them as a philosophy student with very little prior knowledge of the subjects I would come to thoroughly enjoy. A great number of people assisted me in field collections that were vital to the completion of my thesis and, while I wish I had the space to name all of them, I do want to mention Subhronil Mondal and Joshua Slattery, both of whom assisted with critical field collections. Table of Contents List of Tables ...................................................................................................................... ii List of Figures .................................................................................................................... iii Abstract .............................................................................................................................. iv 1. Introduction ......................................................................................................................1 2. Materials and Methods .....................................................................................................4 2.1. Specimen Collection .........................................................................................4 2.2. Experimental Design .........................................................................................4 2.3. Statistical Analysis ............................................................................................7 3. Results ..............................................................................................................................8 3.1. Observations of Competitive Interactions ........................................................9 3.2. Incomplete Drill Holes ....................................................................................11 3.3. Multiple Drill Holes ........................................................................................12 3.4. Consumption Rates and Drilling Durations ....................................................13 3.5. Prey Size .........................................................................................................15 4. Discussion ......................................................................................................................16 4.1. Competitive Interactions and Potential Proxies ..............................................16 4.2. Implications and Potential Applications of Incomplete Drill Holes and the Fossil Record ...................................................................................................18 4.3. Other Observations .........................................................................................19 4.3.1. 'Successful' Incomplete Drill Holes .................................................19 4.3.2. Resumption of Drill Holes ...............................................................20 4.3.3. Multiple, Complete Drill Holes .......................................................21 4.3.4. Scavenging .......................................................................................21 5. Conclusion .....................................................................................................................23 References ..........................................................................................................................25 Appendices .........................................................................................................................29 Appendix I: ............................................................................................................30 Appendix II: ...........................................................................................................31 i List of Tables Table 1: Differences in drilling parameters between treatments .........................................8 Table A1: Tank assignments for predators ........................................................................31 Table A2: Prey size measurements and drilling data for the small group isolation treatment ......................................................................................................................32 Table A3: Prey size measurements and drilling data for the small group competition treatment. .....................................................................................................................34 Table A4: Prey size measurements and drilling data for the large group isolation treatment ......................................................................................................................39 Table A5: Prey size measurements and drilling data for the large group competition treatment ......................................................................................................................40 ii List of Figures Figure 1: Complete and incomplete drilling frequencies ...................................................12 Figure 2: Single and multiple drilling frequencies ............................................................13 Figure 3: Consumption rates ..............................................................................................14 Figure A1: Collection sites ................................................................................................30 Figure A2: Two replicate aquarium setup .........................................................................30 iii Abstract The fossil record of drilling predation has been widely used to study predator-prey interactions and their relative importance on long-term evolutionary processes. Incomplete drill holes have been interpreted as indicators of failed attacks due to well- defended prey. However, this interpretation is based on pair-wise interactions between one predator and one prey, a condition commonly compromised in nature. The hypothesis that interference among drilling predators leads to an increase in the relative frequency of incomplete drill holes was tested in the laboratory using the naticid Neverita delessertiana (Récluz) and a common prey, the bivalve Chione elevata (Say). The experiment consisted of an isolation treatment, where predators fed alone, and a competition treatment, where predators fed in groups of three. Predators in competition were grouped into two size cohorts, small and large. All drilling attacks made by isolated predators of both size groups were successful, resulting in complete drill holes, whereas, in competition, the incomplete drilling frequencies were 6.9% for the small predator group and 21.3% for the large predator group. A range of competitive, predator-predator interactions were observed, including grappling, prey theft, and cannibalism. These results suggest that interpretations of both field and fossil data must consider the role of competitive disruption as an additional source of incomplete drill holes. The implications of other observations, including prey 'suffocation' and the resumption of incomplete drill holes after successful prey theft, are also discussed. iv 1. Introduction The hypothesis of escalation frames biotic interactions as drivers of long-term adaptive trends towards greater power (e.g., metabolism, locomotion, etc.) and control over resources (e.g., nutrients, biogeochemical cycles, etc.), which have been only temporarily disrupted during times of biotic crises (Vermeij, 2006a, 2006b). A competing view argues that external environmental factors (e.g., bolide impacts, extreme climate change, etc.) and intrinsic biotic factors (e.g., developmental