Abstract

PREDATOR OUT OF PLACE: THE DIFFERENTIAL IMPACTS OF NATIVE AND NON-

NATIVE CRAYFISH ON BUFO TADPOLES

By: Patia M. Connell

June, 2010

Chair: Dr. Jeffery McKinnon

Department of Biology

Predators have been shown to alter important fitness components (larval period, mass at metamorphosis, and overall survivorship) of larval anurans. Uncommonly studied predators of tadpoles include crayfish. Both native and introduced crayfish occur in NC. To gain a better understanding of the effect of introduced crayfish in NC, we examined the impact of native

(Procambarus acutus) and introduced (P. clarkii) crayfish on Fowler’s toad larvae (Bufo fowleri). We hypothesized P. clarkii would have a greater effect on fitness components of Bufo fowleri because it is larger, more aggressive and invasive in many parts of the world. Because these two species can co-occur, we conducted an experiment that allowed us to evaluate the independent and interactive effects of the two crayfish species at different densities (0, 1 or 2 individuals present).

We found that crayfish did not alter toad larval period, but reduced toad survival and caused toads to metamorphose at larger masses. The effect of crayfish on toad survival and mass at metamorphosis increased with crayfish density. Interestingly, native crayfish caused a stronger reduction in survival and a stronger enhancement in mass at metamorphosis than did introduced crayfish when present at similar densities. Although toad survivorship in ponds with both

crayfish species was comparable to survivorship in ponds containing only native crayfish, toads metamorphosed at larger sizes when both crayfish species were present. We caution, however,

that P. clarkii can achieve higher densities than native species in some situations and likely have

a more important effect under high-density conditions.

PREDATOR OUT OF PLACE: THE DIFFERENTIAL IMPACTS OF NATIVE AND NON-

NATIVE CRAYFISH ON BUFO TADPOLES

A Thesis

Presented To

The Faculty of the Department of Biology

East Carolina University

In Partial Fulfillment

of the Requirements for the Degree

Masters of Science

by

Patia M. Connell

June, 2010

©Copyright 2010 Patia M. Connell

PREDATOR OUT OF PLACE: THE DIFFERENTIAL IMPACTS OF NATIVE AND NON-

NATIVE CRAYFISH ON BUFO TADPOLES

by

Patia M. Connell

APPROVED BY:

DIRECTOR OF THESIS:______Dr. David R. Chalcraft, PhD

COMMITTEE MEMBER:______Dr. Derek Alderman, PhD

COMMITTEE MEMBER:______Dr. Kyle Summers, PhD

COMMITTEE MEMBER:______Dr. Heather Vance-Chalcraft, PhD

CHAIR OF THE DEPARTMENT OF BIOLOGY

______Dr. Jeffery McKinnon, PhD

DEAN OF THE GRADUATE SCHOOL:

______Paul J. Gemperline, PhD

ACKNOWLEDGEMENTS

I would like to thank my advisor, David Chalcraft, for his guidance over the past few years and for teaching me the careful methodology that good science requires. I’d like to thank the rest of my committee (Derek Alderman, Kyle Summers, and Heather Vance-Chalcraft) for their support and guidance as well. My lab mates have been an invaluable support system and I would like to specifically thank Jon Davenport and Natalie Amoroso for keeping me alive and sane. I am grateful to several people who helped with the project: Zac Aardweg, Freddy Herrera, Matt Prentice, Brooks Lowe, Robby Deans, John Haywood, Bob Connell, Jessica Kingsley, and Jason Hernandez. I am especially grateful to Heather Vance-Chalcraft for the use of her lab and equipment, and for keeping me apprised of opportunities for outreach to the community. I hope to continue working with her in the future. Thanks also to Melissa Meyers and Weyerhaeuser for allowing me to use your facilities at Cool Springs and for the volunteer opportunities you have provided. I would like to thank the te