Divergence in the Ecology of Two Species of Gambusia in Secondary Contact Daniella M
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University of New Mexico UNM Digital Repository Biology ETDs Electronic Theses and Dissertations 5-1-2011 Divergence in the ecology of two species of Gambusia in secondary contact Daniella M. Swenton Follow this and additional works at: https://digitalrepository.unm.edu/biol_etds Recommended Citation Swenton, Daniella M.. "Divergence in the ecology of two species of Gambusia in secondary contact." (2011). https://digitalrepository.unm.edu/biol_etds/105 This Dissertation is brought to you for free and open access by the Electronic Theses and Dissertations at UNM Digital Repository. It has been accepted for inclusion in Biology ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. DIVERGENCE IN THE ECOLOGY OF TWO SPECIES OF GAMBUSIA IN SECONDARY CONTACT BY Daniella M. Swenton B.S., Environmental Science, University of Vermont, 2003 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Biology The University of New Mexico Albuquerque, New Mexico May, 2011 Dedication This dissertation is dedicated to my loved ones. My dad adores exploring nature and inspired that passion in me. Deb is a well of unconditional love & support. My sister, Deborah, & Hank, Bean, Jas, & Mer are the calm anchor to my whipping kite. My mom always encourages me to reach higher. My brothers keep me on my toes and in smiles. Erin, Cyndi, Cara Lea, Sarah, Tansey, Lis, Yadeeh, Maria, Brit, 'Rie, Apple, Fred, Andee, & Shannon are my spiritual and girl-power strength. And finally to Travis, for your one shine. iii Acknowledgements I would like to thank my dissertation committee, Astrid Kodric-Brown, Tom Turner, Blair Wolf, & Joel Trexler. I would also like to acknowledge the support from members of the UNM Biology Department including my friends and colleagues in the Kodric-Brown, Turner, & Wolf labs, especially Lisa Schwanz, Pam Keil, Tom Kennedy, Rick Winslow, and Robin Warne. This dissertation would not have been possible without the support of the stickleback crew, especially John Baker & Susan Foster. Finally, a very special thanks to my dear friend and colleague, Ric Charnov, to whom I owe my fascination with life history theory. iv DIVERGENCE IN THE ECOLOGY OF TWO SPECIES OF GAMBUSIA IN SECONDARY CONTACT BY DANIELLA M. SWENTON ABSTRACT OF DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Biology The University of New Mexico Albuquerque, New Mexico May, 2011 DIVERGENCE IN THE ECOLOGY OF TWO SPECIES OF GAMBUSIA IN SECONDARY CONTACT BY DANIELLA M. SWENTON B.S., Environmental Science, University of Vermont, 2003 Ph.D., Biology, The University of New Mexico, 2011 ABSTRACT Gambusia nobilis, a federally endangered species, and G. affinis (Poeciliidae) are small, livebearing fishes found in the southwestern U.S. The invasive G. affinis has been introduced globally to control mosquito populations. It is found in some populations of G. nobilis on Bitter Lake National Wildlife Refuge (BLNWR), the field site for this study. It is unclear to what extent the two species have diverged in behavior and ecology and how extensively they have hybridized on BLNWR, thereby threatening the endangered G. nobilis via genetic introgression. In this study I examined divergence in behavior and ecology between two species with four main objectives: (1) To determine if there is assortative mating between the two species; (2) To determine if there is divergence in life history characteristics between the two species; (3) To assess habitat and dietary differences between extant populations of the two species; and (4) To determine the degree to which the two species have genetically introgressed on BLNWR. I found these two fishes are markedly different in behavior and ecology. Males and females of both species show assortative preference in visual/olfactory tests. This vi assortative preference pattern was held during copulation, probably as a function of female choice. Data from field caught and lab breeding individuals show differences in key life history traits that reflect the trade-offs in their current environments. To assess ecological divergence I characterized the habitats of the two species. G. affinis persists in ephemeral environments and G. nobilis is restricted to spring-fed, stenohaline and stenothermal habitats. The two species also show differences in ecological niche as G. nobilis appears to feed at a higher trophic level. Finally, I characterized genetic patterns of hybridization. I found low genetic diversity for G. nobilis, probably a result of range contraction. Gene flow and rates of hybridization are low providing further evidence for divergence and reproductive isolation between these two species. The results presented here include characterization of the habitat requirements, heterospecific interactions, and population genetics of these two species on BLNWR and may be helpful to management of a sensitive species such as G. nobilis. vii TABLE OF CONTENTS List of Figures .................................................................................................................. xii List of Tables ................................................................................................................... xv Chapter 1: Sex Differences in Mate Preference between Two Hybridizing Species of Poeciliid Fish ............................................................................................................ 1 Abstract ..................................................................................................................... 1 Introduction ............................................................................................................... 1 Methods ..................................................................................................................... 5 Fish collection and maintenance. ..................................................................... 5 Trial methods. .................................................................................................. 5 Visual/Olfactory tests. ..................................................................................... 6 Open mating tests. ........................................................................................... 7 Data analysis. ................................................................................................... 8 Results ....................................................................................................................... 9 Visual/Olfactory tests. ..................................................................................... 9 Open mating tests. ......................................................................................... 10 Discussion ............................................................................................................... 12 Acknowledgements ................................................................................................. 14 References ............................................................................................................... 16 Tables and Figures .................................................................................................. 22 Chapter 2: Habitat and Life History Differences between Two Species of Gambusia ................................................................................................................................. 26 Abstract ................................................................................................................... 26 viii Introduction ............................................................................................................. 27 Methods ................................................................................................................... 30 Field study. .................................................................................................... 30 Laboratory breeding. ...................................................................................... 31 Dissections of fish from museum collections. ............................................... 32 Data analysis. ................................................................................................. 33 Results ..................................................................................................................... 34 Habitat characteristics. ................................................................................... 34 Demographic patterns during the breeding season. ....................................... 34 Maternal investment. ..................................................................................... 35 Discussion ............................................................................................................... 36 Acknowledgements ................................................................................................. 41 References ............................................................................................................... 43 Tables and Figures .................................................................................................. 48 Chapter 3: The Use of δ15N and δ13C to Assess Feeding Niche Space of Fishes in a Desert Spring System ............................................................................................ 56 Abstract ..................................................................................................................