THE EVOLUTION OF PHENOTYPIC VARIATION IN ANABRUS SIMPLEX (ORTHOPTERA: TETTIGONIIDAE): SHAPE DIFFERENCES IN MORPHOLOGY AND PATTERNS OF MORPHOLOGICAL INTEGRATION IN MORMON CRICKETS A thesis submitted to Kent State University in partial fulfillment of the requirements for the degree of Master of Science by Stacy Rae Neal August, 2009 Thesis written by Stacy Rae Neal B.A., The State University of New York, Stony Brook, 2003 M.A., Kent State University, 2009 Approved by _____________________________________, Dr. Patrick Lorch, Advisor, Department of Biological Sciences _____________________________________, Dr. James Blank, Chair, Department of Biological Sciences _____________________________________, Timothy Moerland, Dean, College of Arts and Sciences ii TABLE OF CONTENTS ACKNOWLEDGEMENTS…………………………………………………………...vii LIST OF FIGURES……………………………………………………………………iv LIST OF TABLES……………………………………………………………………..vi CHAPTER I. Introduction…………………………………………………………………1 Natural History of Anabrus simplex (Orthoptera:Tettigoniidae)……......1 Techniques for Investigating Shape Differences in Morphology and Morphological Integration………………………………………………6 Materials and Methods………………………………………………......7 The Contact Call Hypothesis for Cohesive Movement in Mormon crickets…………………………………………………………………10 II. A Preliminary Study of Morphology in Mormon Crickets………………..12 Introduction…………………………………………………………….12 Methods………………………………………………………………...14 Results………………………………………………………………….18 Discussion………………………………………………………………25 III. Shape differences in Morphology in Mormon Crickets…………………....28 Introduction……………………………………………………………...28 Study Questions………………………………………………………....30 Methods………………………………………………………………….33 Results: Principal Component Analysis………………………………....39 Results: Shape Differences Between BF and NBF Mormon crickets…...48 Results: Shape Differences Between Three Population Types…………..54 Results: Correlations Between Morphology and Movement Rate………59 Discussion………………………………………………………………..64 IV. Patterns of Morphological Integration in Mormon Crickets……………….75 Introduction………………………………………………………………75 Study Questions………………………………………………………….78 Methods…………………………………………………………………..83 Results…………………………………………………………………....84 Discussion………………………………………………………………..87 V. Conclusion…………………………………………………………………….93 iii LITERATURE CITED…………………………………………....................................100 LIST OF FIGURES Figure 1.1……………………………………………………………………………….3 Figure 1.2……………………………………………………………………………….4 Figure 2.1………………………………………………………………………………15 Figure 2.2………………………………………………………………………………16 Figure 2.3………………………………………………………………………………17 Figure 2.4………………………………………………………………………………20 Figure 2.5………………………………………………………………………………21 Figure 2.6………………………………………………………………………………22 Figure 2.7………………………………………………………………………………23 Figure 3.1………………………………………………………………………………35 Figure 3.2………………………………………………………………………………35 Figure 3.3………………………………………………………………………………36 Figure 3.4………………………………………………………………………………36 Figure 3.5………………………………………………………………………………37 Figure 3.6………………………………………………………………………………37 Figure 3.7………………………………………………………………………………38 Figure 3.8………………………………………………………………………………38 Figure 3.9………………………………………………………………………………41 Figure 3.10……………………………………………………………………………..45 iv Figure 3.11……………………………………………………………………………..50 Figure 3.12……………………………………………………………………………..51 Figure 3.13……………………………………………………………………………..52 Figure 3.14……………………………………………………………………………55 Figure 3.15……………………………………………………………………………56 Figure 3.16……………………………………………………………………………57 Figure 3.17……………………………………………………………………………57 Figure 3.18……………………………………………………………………………60 Figure 3.19……………………………………………………………………………61 Figure 3.20……………………………………………………………………………62 Figure 3.21……………………………………………………………………………63 v LIST OF TABLES Table 2.1………………………………………………………………………………24 Table 2.2………………………………………………………………………………24 Table 2.3………………………………………………………………………………24 Table 2.4………………………………………………………………………………24 Table 2.5………………………………………………………………………………24 Table 3.1………………………………………………………………………………32 Table 3.2………………………………………………………………………………43 Table 3.3………………………………………………………………………………43 Table 3.4………………………………………………………………………………43 Table 3.5………………………………………………………………………………44 Table 3.6………………………………………………………………………………44 Table 3.7………………………………………………………………………………46 Table 3.8………………………………………………………………………………47 Table 3.9………………………………………………………………………………47 Table 3.10……………………………………………………………………………..47 Table 3.11……………………………………………………………………………..48 Table 3.12……………………………………………………………………………..53 Table 3.13……………………………………………………………………………..58 Table 3.14……………………………………………………………………………..64 Table 4.1………………………………………………………………………………86 Table 4.2………………………………………………………………………………87 vi ACKNOWLEDGEMENTS This thesis would not have been possible without Dr. Patrick Lorch, his invaluable experience with Mormon crickets in the field, or his lab resources. I would like to especially thank Dr. Christopher Vinyard whose expertise and guidance were also essential to the completion of this project, and Dr. Mark Kershner, who also provided guidance as a committee member. Many thanks to Dr. Darryl Gwynne and Dr. Kevin Judge of the University of Toronto for providing a large dataset of Mormon cricket morphometrics for the analyses in Chapter 2. Bob Srygley and Laura Senior provided assistance with radio tracking the Mormon crickets in Eagle Rock, NV in 2008. Justin Reeves provided helpful comments on the thesis. Dr. Richard Meindl assisted with some of the multivariate statistics used in this thesis. I would also like to thank my parents, Cindy and Tim Fahey who have been so helpful, especially regarding my academic pursuits. Lastly, Orin Neal was extremely supportive throughout the process of completing this thesis and I also thank him for his encouragement to proceed with my studies in evolutionary biology. vii CHAPTER I: INTRODUCTION NATURAL HISTORY OF ANABRUS SIMPLEX (ORTHOPTERA: TETTIGONIIDAE) Tettigoniidae is a large and diverse family of insects in the order Orthoptera. Other Orthopterans include the grasshoppers, locusts, and crickets, and the Tettigoniidae are known as katydids or bush-crickets. Males and some female tettigoniids are capable of song production via stridulation of the wings which feature sound producing organs. Calling in katydids is presumed to be a courtship display, possibly the sole method of mate finding or mate attraction, and song complexity is likely to have evolved under pressures including predation avoidance and sexual selection (Bailey & Rentz 1990). The Tettigoniinae are the shield-backed katydids and there are roughly 500 species in this subfamily that inhabit temperate or tropical environments (Bailey & Rentz 1990). Anabrus simplex (Orthoptera: Tettigoniidae) are flightless North American shield- backed katydids commonly called Mormon crickets that exist with a broad distribution of phenotypes. Body size, coloration, daily movement, calling behavior, and mating structure are among the known differences between population types (Gwynne 1981, Lorch & Gwynne 2000, Gwynne 2001, Bailey et al 2005, Bailey et al 2007a, Bailey et al 2007b). Populations of Mormon crickets are typically classified as either gregarious or solitary based on estimates of population density, however, these terms also tend to be synonymous with band-forming or non-band-forming behavior which can be quantified 1 2 using radio telemetry (Lorch & Gwynne 2000, Gwynne 2001, Bailey et al 2005). Mormon crickets are referred to here as band-forming (BF) or non-band-forming (NBF) depending on estimated relative population density and movement behavior recorded by radio telemetry. Mormon crickets that are intermediate to the typical population types in these characteristics are referred to here as intermediate. Recent studies of mtDNA in Mormon crickets revealed a genetic division that generally corresponds to eastern NBF and western BF population types that appear to have discrete evolutionary histories over the last two million years (Bailey et al 2005, Bailey et al 2007a, Bailey et al 2007b). Populations of large-bodied Mormon crickets generally found west of the Rocky Mountains often form outbreaks with dense bands that exhibit rapid, cohesive movement over long distances (Cowan 1929; Wakeland 1959; MacVean 1987; Lorch & Gwynne 2000; Gwynne 2001, Lorch et al 2005, Sword et al 2005a, Sword et al 2005b). These outbreak, or BF populations of Mormon crickets are stressed for protein and salt due to an increase in feeding competition with increased population density (Lorch et al. 2005; Sword et al. 2005a, Simpson et al 2006), and may exhibit reversed sex roles. Under these conditions, females must compete for access to males for the nutrient-rich nuptial gifts that they receive upon mating (Gwynne 1981, Lorch & Gwynne 2000; Gwynne 2001). The nuptial gift is a spermatophore produced by males of many species of katydid that is transferred to the female during mating, and the nutrients it contains have been shown to influence female fecundity and offspring survival (Bailey & Rentz 1990, Gwynne 2001). It is presumed to be a limiting factor for females in BF populations when feeding competition is high and the females must compete for males in order to receive 3 this additional nutrition. Males in the BF populations make short, low intensity calls which occur while the “bands” are moving (Gwynne 2001, Bailey et al 2007b, Neal personal observation). The relationship between the call structure and sex role reversal in this population type is currently unknown. In addition to the outbreak populations, there are populations of smaller-bodied, relatively sedentary NBF Mormon crickets, which are solitary and exhibit