Copyright by Laura Elizabeth Dugan 2014 The Dissertation Committee for Laura Elizabeth Dugan Certifies that this is the approved version of the following dissertation: Invasion Risk and Impacts of a Popular Aquarium Trade Fish and the Implications for Policy and Conservation Management Committee: Dean Hendrickson, Supervisor Camille Parmesan, Co-Supervisor Hans Hofmann Mathew Leibold Mary Poteet Invasion Risk and Impacts of a Popular Aquarium Trade Fish and the Implications for Policy and Conservation Management by Laura Elizabeth Dugan, B.S. Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin May 2014 Dedication This dissertation is dedicated to my family, fellow pursuers of knowledge, who have always encouraged, motivated and supported me and my academic interests. I could not have come this far without you. "The idea of wilderness needs no defense. It only needs more defenders." Edward Abbey Acknowledgements I would like to thank my advisor Dean Hendrickson for the opportunity to work on this interesting topic in such a beautiful place. I would also like to thank my advisors Dean Hendrickson and Camille Parmesan, my committee members Hans Hofmann, Mathew Leibold and Mary Poteet and the Parmesan lab members for all their support and invaluable input on this work. In addition, without the assistance of my colleagues in Cuatro Ciénegas as well as several undergraduate students and local Cuatro Ciénegas volunteers, this work would not have been possible. Lastly, I would like to acknowledge funding support from the following sources: Dorothea Bennett Memorial Graduate Fellowship Program, Theresa Lozano Long Institute of Latin American Studies México Summer Research Grant Program, Sigma Xi, American Cichlid Association, UT Austin EEB Research Grant Program, the NSF GK-12 International Research Grant, and grants to Parmesan from the National Science Foundation Earth Systems Modeling program (grant #1049208) and the National Institute of Climatic Change Research (#09-NICCR-1077). vi Invasion Risk and Impacts of a Popular Aquarium Trade Fish and the Implications for Policy and Conservation Management Laura Elizabeth Dugan, Ph.D. The University of Texas at Austin, 2014 Supervisors: Dean Hendrickson and Camille Parmesan Invasive species, a top threat affecting global biodiversity, become invasive through a process including four stages: transport, establishment, spread, impact and integration. Species currently in this process provide opportunities to empirically derive the mechanisms driving each of these stages, make predictions based on these mechanisms and then to test these predictions. This research examines the current invaded distribution, potential invasion and community-level impacts of a popular aquarium trade fish (Hemichromis guttatus Günther, 1862) in an endemic hotspot, Cuatro Ciénegas, in Coahuila, México and discusses the policy and conservation management implications of these findings. In Chapter 1, the problem of invasive species, the study site and the focal species of this work are introduced. In Chapter 2, the critical thermal minimum and maximum temperature limits and temperature preference of H. guttatus are identified because temperature is hypothesized to be an important factor controlling this fish’s distribution. The results indicate that H. guttatus has a wide temperature tolerance range (a characteristic of a ‘good’ invader), that preference is a more informative metric for predicting invasion than absolute tolerances, and that resource-poor environments may vii promote searching behaviors that cause an invasive fish to increase its range. In Chapter 3, the results of a field survey are analyzed and temperature, pH, depth and the presence of vegetation are all found to be related to H. guttatus presence. Invasion risk of several as- of-yet uninvaded sites in Cuatro Ciénegas is assessed. In Chapter 4, competitive and predatory interactions of H. guttatus on an endemic, threatened cichlid (Herichthys minckleyi) and a macroinvertebrate community respectively are investigated. The results suggest that while H. guttatus does not directly impact H. minckleyi through competition in these conditions, it may inhibit reproduction and alter H. minckleyi’s behavior through aggressive interactions. In Chapter 5, all results are synthesized and a determination of the invasive status of H. guttatus in Cuatro Ciénegas is made. The results presented here will be useful in identifying areas with a high risk of invasion by this popular ornamental fish, thus allowing the implementation of policy and management actions to prevent or at least ameliorate the impacts of an invasion and will add to the growing knowledge of how invasive species affect native systems. viii Table of Contents List of Tables ........................................................................................................ xii List of Figures ...................................................................................................... xiv Chapter 1: Introduction ............................................................................................1 Chapter 2: Motivational state affects temperature preference but not tolerance in a potentially invasive fish: implications for invasion risk .................................7 Introduction .....................................................................................................7 Methods.........................................................................................................10 Study species and acclimation housing environment ..........................10 Critical Thermal Maximum .................................................................11 Experimental housing environment ............................................11 Testing apparatus ........................................................................12 Test procedure .............................................................................12 Critical thermal minimum ....................................................................13 Test apparatus .............................................................................13 Test procedure .............................................................................14 Critical thermal analyses ......................................................................14 Temperature preference .......................................................................14 Experimental housing environment ............................................14 Test apparatus .............................................................................15 Test procedure .............................................................................16 Temperature preference analysis .........................................................17 Temperature preference determination .......................................17 Comparison of motivational states..............................................18 Results ...........................................................................................................19 Critical thermal maximum ...................................................................19 Critical thermal minimum ....................................................................20 Temperature Preference .......................................................................20 Discussion .....................................................................................................21 ix Critical thermal minimum and maximum ............................................22 Temperature preference .......................................................................25 Policy implications...............................................................................28 Conservation management implications ..............................................30 Conclusions ..........................................................................................31 Chapter 3: Predicting invasion risk of an exotic aquarium trade fish in a desert spring system ...........................................................................................................44 Introduction ...................................................................................................44 Methods.........................................................................................................47 Study site ..............................................................................................47 Data collection .....................................................................................48 Analysis................................................................................................50 Model Building ....................................................................................51 Model Selection ...................................................................................53 Prediction of Invasion Risk in Cuatro Ciénegas ..................................54 Results ...........................................................................................................55 Sampling data.......................................................................................55 Environmental data ..............................................................................56 Model results ........................................................................................57