University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 8-2009 Morphological convergence and character displacement in two species of polymorphic salamanders (genus Plethodon) in eastern Tennessee Jason R. Jones University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Biology Commons Recommended Citation Jones, Jason R., "Morphological convergence and character displacement in two species of polymorphic salamanders (genus Plethodon) in eastern Tennessee. " Master's Thesis, University of Tennessee, 2009. https://trace.tennessee.edu/utk_gradthes/90 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Jason R. Jones entitled "Morphological convergence and character displacement in two species of polymorphic salamanders (genus Plethodon) in eastern Tennessee." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Ecology and Evolutionary Biology. Benjamin M. Fitzpatrick, Major Professor We have read this thesis and recommend its acceptance: James Fordyce, Daniel Simberloff Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a thesis written by Jason R. Jones entitled “Morphological convergence and character displacement in two species of polymorphic salamanders (genus Plethodon) in eastern Tennessee.” I have examined the final paper copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Ecology and Evolutionary Biology. Benjamin M. Fitzpatrick, Major Professor We have read this dissertation and recommend its acceptance: James Fordyce Daniel Simberloff Acceptance for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official student records.) Morphological convergence and character displacement in two species of polymorphic salamanders (genus Plethodon) in eastern Tennessee A Thesis Presented For the Master of Science Degree The University of Tennessee, Knoxville Jason R. Jones August 2009 Dedication This manuscript is dedicated to Dr. Tom Haggerty, Dr. Terry Richardson, and Dr. Paul Kittle at the University of North Alabama, all true naturalists and professionals that further ignited my passion for biology and inspired me to set my sights for higher professional goals, to my uncle and friend Pat Jones, and my best friend, Robin Dunmire Long, both fellow admirers and eternal students of nature, and my two favorite people with whom to walk in the woods. ii Acknowledgements I would like to thank Ben Fitzpatrick, my advisor, for selflessly providing countless hours of his time in lab, office, and field, to propel me towards the completion of this degree, as well as inspiring (and instructing) me with his wizardry in R. I would also like to thank Jim Fordyce and Dan Simberloff for their immeasurably helpful dedication and service as members of my graduate committee, and for their insightful commentary throughout the writing process. I also wish to thank Jonathan Pruitt, Sarah Duncan, Stesha Pasachnik, Megan Todd-Thompson, Dylan Dittrich-Reed, Windy Bunn, Raina and Remy Fitzpatrick, and Allen Higdon for field assistance in wrangling the slippery and often elusive study subjects, Ann Reed and Bob Muenchen for statistical advice, Lisa McDonald, Kerry Hansknecht, Matt Niemiller, Graham Reynolds, Romina diMarco, Premal Shah, and Darrin Hulsey for comments and suggestions, Paul Super, Keith Langdon, and Bill Commins (all with the National Park Service), Roger McCoy (Tennessee Department of Environment and Conservation), and Richard Kirk and Marie Gunney (Tennessee Wildlife Resources Agency) for cooperation in obtaining permits, and the Department of Ecology & Evolutionary Biology at the University of Tennessee, for the provision of a graduate teaching assistantship throughout my duration within the department. Additional thanks also go out to Allen Higdon, who endured the bulk of my madness during the entire thesis-writing process, as well as to all of my family and friends, for their continued love and support. iii Abstract In situations involving the co-occurrence ecologically similar species, one of two different evolutionary responses is often expected. If sympatry results in competition over a shared resource, character displacement would be a favored outcome, while morphological convergence is an alternative outcome if the species have similar responses to the shared environment. In this study, I examine cranial morphology and dorsal coloration of two ecologically similar salamander species (Plethodon serratus, the Southern Red-backed Salamander, and P. ventralis, the Southern Zig-zag Salamander) to evaluate the alternative hypotheses of character displacement or convergence. Results from linear morphometrics analyses showed no significant shifts in morphology of either species suggestive of either character displacement or convergence in any of the measured traits. However, geometric morphometric analyses showed significant morphological convergence of the two species in sympatry. In contrast, the presence or absence of a dorsal stripe showed evidence of character displacement, corroborating an earlier claim made by Highton. These results are unexpected in that features associated with feeding (cranial morphology) are expected to often exhibit character displacement if dietary resource partitioning is an important mechanism of coexistence, whereas coloration might be expected to show local convergence if its primary function is camouflage or aposematism. Convergence might reflect the overwhelming influence of developmental responses to shared environments or convergent adaptation to local prey communities. Displacement with respect to color polymorphism might be consistent with frequency-dependent selection maintaining alternative ways of being cryptic. iv Table of Contents I. Introduction ................................................................................................................................. 1 II. Materials and Methods ............................................................................................................... 6 Study species ............................................................................................................................... 6 Sampling ..................................................................................................................................... 7 Evaluation of dorsal coloration as either continuous or polymorphic in Plethodon ventralis .... 8 Traditional (linear) morphometrics ............................................................................................. 8 Geometric morphometrics ........................................................................................................ 10 Statistical Methods .................................................................................................................... 11 III. Results ..................................................................................................................................... 15 IV. Discussion ............................................................................................................................... 17 References ..................................................................................................................................... 25 Appendices .................................................................................................................................... 37 Appendix A: Tables .................................................................................................................. 38 Appendix B: Figures ..................................................................................................................... 45 Appendix C: Supplemental Material ............................................................................................ 55 Vita ................................................................................................................................................ 59 v List of Tables Table 1. List of measurements and corresponding landmarks for endpoints of distances used in linear morphometric analyses. .............................................................................................. 39 Table 2. Tests of linear measurements and ratios in sympatry versus allopatry. .......................... 40 Table 3. MANCOVA of GPA aligned coordinates. ..................................................................... 41 Table 4. Mahalanobis (first value, above diagonal) and Procrustes (second value, above diagonal) distances and associated P-values (below diagonal) of mean shapes between sympatric and allopatric populations of each species, after correcting for effects of site- specific allometry.