UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ Seismic Communication in a Wolf Spider A thesis submitted to the Division of Research and Advanced Studies Of the University of Cincinnati In partial fulfillment of the requirements for the degree of MASTER’S OF SCIENCE (M.S.) In the department of Biological Sciences of the McMicken College of Arts and Sciences 2005 By Jeremy S. Gibson B.S. Northern Kentucky University, 2000 Committee: Dr. George W. Uetz, Chair Dr. Elke Buschbeck Dr. Kenneth Petren ii Abstract I investigated the importance of the seismic component, substratum-borne vibrations, of the multimodal courtship display in the wolf spider Schizocosa ocreata (Hentz) (Araneae: Lycosidae). It is currently known that the visual signaling component of male multimodal courtship displays conveys condition-dependent information, and that females can use this signal alone in mate choice decisions. I found that isolated seismic signals are also used in mate choice, as females preferred males that were louder, higher pitched and with shorter signaling pulses. Results also showed that male seismic signals are dependent on current condition and may convey information about male size and body condition. Seismic signals and visual signals are likely redundant, although some aspects of seismic signals may convey different information, supporting both the redundant and multiple messages hypotheses. i ii Acknowledgements I would foremost like to thank Dr. George Uetz, my graduate advisor for all of his support throughout this adventure. His time investment in my mentoring has meant more to me than I can possibly convey in words, but I will attempt to covey some of my thoughts and feelings. I know I haven’t told him often enough how much I have appreciated his patience and understanding concerning the several issues I faced while matriculating through UC’s graduate program. He has not only made me a better thinker and scientist he has also helped me to vastly improve my scientific writing. George, thank you so much! My graduate research committee which was made up of Dr. Ken Petren and Dr. Elke Buschbeck were also very instrumental in my success at UC. They were always willing to supply feedback and support when ever I asked. They made and continued to make wonderful suggestions and positive feedback on all portions of my research. Their dedication to understand and help me definitely added to my success. Other faculty at UC also helped at various stages of my research progress, despite not having an actual connection with my research. Dr. Theresa Culley was always willing to answer statistics-related questions along with helping me setup SAS to run repeated measures logistic regression analysis. Dr. Steven Pelikan further supported some of my statistical inquires and helped me isolated the appropriate statistics for parts of my research. Thank you both for your contributions! There are numerous peers and undergraduates to thank for helping me through my graduate experience at UC. I would particularly like to extend a very large thank you to my iii fellow graduate students, Casey Harris, Julee Johns, Matt Klooster, Anne Lohrey, Jenai Milliser, Dr. J. Andrew Roberts, and Kerri Wrinn; they were instrumental in my mental health throughout this process. Not only did several of these people help in spider care and rearing a couple of them even helped setup spiders for experiments. Thanks guys and gals! Spider care and collection would have been a nightmare without the help of some very dedicated undergraduates, Stephanie Doherty, Shanquala Pruitt, Melissa Salpietra and Erin White. I would particularly like to thank Shanquala Pruitt for all of her assistance when the majority of this research was conducted. Her work ethic and timeliness was absolutely invaluable to the success of this project. Without her assistance in spider care and rearing a large portion of this research would have been lost. Thanks so much! A very special “thank you” goes to my family. They have shown me unconditional support and love through this process, despite many of them having no real understanding of the trials and tribulations I faced. I would definitely like to thank my Mother, Carole Warner, who showed me that no matter how big I dreamt, with dedication and the desire to succeed it was reachable. Thank you so much for all of your years of hard work to provide me with everything and more! I love you! I’d also like to thank my Grandmother, Madeline Goose, whom would go to mars and back if she had to, just for me. I love you too, thank you! One special person deserves a heartfelt thank you for having to put up with me day in and day out, Keena Cole, my wife. Thank you for all of your support both mental and financial! You have been my foundation, unwavering and unbreakable throughout! Thank you for being so wonderful! iv Table of Contents Abstract i Acknowledgements iii List of Tables 2 List of Figures 3 Chapter Page I. Introduction 5 • Study Organism 5 • Research Objectives / Hypotheses 7 • References 9 II. Male Seismic Courtship Communication and Female Receptivity 11 in a Wolf Spider (Araneae: Lycosidae) • Abstract 12 • Introduction 13 • Methods 16 • Results 21 • Discussion 23 • Acknowledgements 25 • References 27 • Tables and figures 32 III. Effect of Rearing Environment and Feeding on Dynamic and 39 Static Attributes of Male Seismic Communication • Abstract 40 • Introduction 41 • Methods 43 • Results 48 • Discussion 52 • Acknowledgements 55 • References 57 • Tables and figures 61 IV. Conclusion and Future Direction 72 1 List of Tables and Figures Tables Page Table 2.1: Stepwise multiple logistic regression analysis for attributes of 35 percussive strikes alone. A lack of fit value close to 1.0 indicates a strong statistical result. Table 2.2: Stepwise multiple logistic regression analysis for attributes of 35 seismic pulses. A lack of fit value close to 1.0 indicates a strong statistical result. Table 2.3: Stepwise multiple logistic regression analysis for the combined 36 significant attributes for both percussive strikes and seismic pulses. A lack of fit value close to 1.0 indicates a strong statistical result. Table 2.4: Stepwise multiple logistic regression analysis for attributes of male 36 courtship behavior. A lack of fit value close to 1.0 indicates a strong statistical result. Table 2.5: Pearson’s pairwise correlation analysis results for seismic attributes 37 on aspects of male morphology and condition. r2(p-value) Table 2.6: Seismic signal attribute levels of highly successful (3 receptive 38 females), successful (>0 receptive females) and unsuccessful males (0 receptive females). The letter “S” stands for a static trait while “D” means dynamic. Table 3.1: Pearson pairwise correlation matrix results between male seismic 70 attributes and aspects of male size, condition and traits. “S” stands for static traits, while “D” stands for dynamic traits. All significant values have been highlighted; while values that maybe approaching significance are underlined and italicized. Table 3.2: ANOVA table comparing laboratory-reared (LR), field-caught 71 (FC), field-caught-fed (FC-F), and field-caught-starved (FC-S) spiders. Post-hoc Tukey tests are given (under treatment group), same letters indicate statistical similarity while different letters indicate statistical difference. 2 Figures Page Figure 2.1: A male S. ocreata, with conspicuous tufts. 32 Figure 2.2: Cue isolation apparatus: a) female chamber, b) male chamber, c) 32 visual barrier, d) point of recording. Figure 2.3: Laser Doppler vibrometer setup with cue isolation apparatus. 33 Figure 2.4: Representative spectra of a sample of male seismic courtship. A) 34 Time signal (waveform) highlighting the two fundamentally different signal components. B) Close up view illustrating percussive strike temporal measurements. C) Close up view of seismic pulse temporal measurements. D) FFT-spectrogram taken from ‘B’ illustrating amplitude and frequency. Figure 3.1: Recording platform: a) male chamber, b) point of recording 61 Figure 3.2: Comparison of laboratory-reared and field-caught spiders by 62 rearing environment for; (A) male size (cephalothorax width), (B) male mass, and (C) male body condition index (residuals of a regression analysis of mass by cephalothorax width) Figure 3.3: Comparison of behavioral rates for the two components of jerky- 63 tapping between laboratory-reared and field-caught spiders. Figure 3.4: Comparison of two dynamic seismic signal attributes between 64 laboratory-reared and field-caught spiders, (A) percussive strike peak amplitude and (B) seismic pulse duration. Figure 3.5: Comparison of two static seismic signal attributes between 65 Laboratory-reared and field-caught spiders, percussive strike peak frequency and percussive strike maximum frequency. Figure 3.6: Comparison of dynamic male traits over time (initial = time 0 and 66 final = after 14 days) between starved and fed field-caught male spiders. (A) mean percent change in male mass. (B) mean percent change in male body condition index. p-value of <0.0001 is indicated by ***. Figure 3.7: Comparison of static seismic signal attributes over time (initial = 67 time 0 and final = after 14 days) between field-caught fed and starved spiders. (A) Mean percussive strike peak frequency repeated measures. (B) Mean percussive strike maximum frequency. 3 Figures Page Figure 3.8: Comparison of dynamic seismic signal attributes over time (initial 68 = time 0 and final = after 14 days) between field-caught fed and starved spiders. (A) Mean percussive strike peak amplitude. (B) Mean seismic pulse duration. p-value of <0.005 is indicated by **. Figure 3.9: Comparison of dynamic behavioral components over time (initial = 69 time 0 and final = after 14 days) between field-caught fed and starved spiders.