Testing the Ecological and Physiological Factors Influencing Reproductive Success in Mosses
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Portland State University PDXScholar Dissertations and Theses Dissertations and Theses Summer 8-4-2014 Testing the Ecological and Physiological Factors Influencing Reproductive Success in Mosses Erin Elizabeth Shortlidge Portland State University Follow this and additional works at: https://pdxscholar.library.pdx.edu/open_access_etds Part of the Other Plant Sciences Commons, and the Plant Biology Commons Let us know how access to this document benefits ou.y Recommended Citation Shortlidge, Erin Elizabeth, "Testing the Ecological and Physiological Factors Influencing Reproductive Success in Mosses" (2014). Dissertations and Theses. Paper 1951. https://doi.org/10.15760/etd.1950 This Dissertation is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. Testing the Ecological and Physiological Factors Influencing Reproductive Success in Mosses by Erin Elizabeth Shortlidge A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biology Dissertation Committee: Sarah Eppley, Chair Daniel Ballhorn Catherine de Rivera Jason Podrabsky Todd Rosenstiel Portland State University 2014 © 2014 Erin Elizabeth Shortlidge Abstract As non-vascular, early land plants with an aquatic ancestry, mosses do not regulate internal water conditions separate from that of their environment and as a result, evolved mechanisms to survive in a terrestrial world out of water. Yet, there is a widely accepted dogma that moss reproductive success is solely dependent on rainfall events carrying swimming, bi-flagellate sperm across the landscape to reproductively mature and receptive female mosses – but this classic view of moss reproduction may be too simplistic. In this dissertation I test the assumptions of reproductive limitation in mosses and present novel findings in a basal, yet understudied terrestrial plant mating system. I find evidence of environmental desiccation tolerance in moss sperm, thus offering the potential for stress-tolerant gametes on the landscape possibly suited for various transport vectors, reminiscent of a pollen grain. To investigate the broad evolutionary implications of this newfound complexity in moss sexual reproduction, I tested classic tenets of plant- pollinator theory on the ancient mosses and their ubiquitous microarthropod inhabitants. Experimental results show that mosses and microarthropods are engaged in a “pollination–like” syndrome guided by sex-specific volatile cues that differentially affect microarthropod behavior. These data indicate an existing complex mutualistic relationship and provides new evidence of sexually dimorphic investment by male and female mosses into reproductive i success. Further, these data put forth the idea that female mosses challenge an inherent mate limitation by investing into reproductive assurance via maintaining a relationship with microarthropods. Experimental work further confirms a role for invertebrates in moss reproductive success and tests mutualism theory through ongoing experiments. Such experiments include an assessment of moss genetic diversity, paternity, and male fitness traits as it relates to mosses with or without the presence of microarthropods, thereby testing for fitness benefits gained by mosses possibly engaged in a transport mutualism with microarthropods. I further tested mutualism, community ecology and moss sexual reproduction concepts in extreme geothermal moss populations living at the edges of inhabitable Earth, and results show that even geothermal moss canopies are diverse and host differential and abundant life. In a first field test of mutualism I found that although extreme heat stress may constrain sexual reproduction in mosses, a correlation between within-population moss genetic diversity and microarthropod abundances exists. To further examine mosses in extreme environments, and how these environments may constrain sexual reproductive success, I evaluated the effects of simulated warming on Antarctic moss physiology and reproductive biology. Data indicates that simulated warming relieves mosses of physiological stress, and results in a greater investment into primary productivity and sexual reproduction. These ii data support the hypothesis that with less stress, sexual reproduction is increased. Mosses are an ideal system by which to understand organisms that exist in environments ranging from the mesic to the extreme, in the laboratory and the field and even in the classroom, where the small functioning ecosystem of mosses can be used for discovery-based biology education as described in the Mosscosms curriculum. Overall, this work contributes significantly to the field of bryophyte and plant biology by revealing novel insights into the biotic and abiotic factors influencing sexual reproduction in mosses. iii The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. He who knows it not and can no longer wonder, no longer feel amazement, is as good as dead, a snuffed-out candle. Albert Einstein, The World as I See it (1931) iv Acknowledgements First and foremost I would like to acknowledge the never-ending love from my mom – no matter what my diverse endeavors have been, you have supported them. I would like to thank my cat Emmett who has sat on my keyboard and/or halfway over my right arm for at least half of the words written in this dissertation. I thank my advisor Sarah Eppley for her ability to always see the path forward although it was not always clear to me. You have believed in my ability to conquer this PhD and I deeply appreciate your confidence and continuous generosity. I clearly would not be here, writing this without you. I thank Todd Rosenstiel for invaluable insights and endless encouragement as well as Suzanne Estes and Jason Podrabsky for general scientific, moral and logistical support, even at a moment’s notice. I also would like to thank Catherine de Rivera for years of support and guidance, and Daniel Ballhorn for your insight. I am grateful for the opportunity to participate in the GK-12 program as it allowed me work with incredible students and helped me to see what aspects of my scientific endeavors actually matter the most. The fieldwork and life I experienced in Antarctica with Angelica Casanova-Katny are incomparable, and to everyone that I have been lucky enough to collaborate with - your talents are definitely not lost on me. v I thank my labmates both past and present who have played a role of support and understanding that cannot be replicated outside of our insular world, and the undergraduates and post-bacs who worked diligently and sometimes tirelessly to help me with data collection. I would like to acknowledge the funding sources that have allowed me to pursue this work and have enabled the experiences that I have gained along the way. I also would like to thank my constant work companions: A few particular albums listened to on constant repeat while experiments were set- up, maintained, and data collected, as well as most of Oregon Public Broadcasting’s programming. Also, thank you to Besaw’s. And finally, I owe so much to my family and friends - both in Portland and far away, you know who you are, and each of you are very much appreciated and loved. I may not have made it through this (or any) phase of my life without you being there to tirelessly pick up the line when the phone calls came in. Thank you. vi Table of Contents Abstract..................................................................................................................i Dedication............................................................................................................iv Acknowledgements...............................................................................................v List of Tables.......................................................................................................ix List of Figures.......................................................................................................x Chapter 1 Introduction..........................................................................................................1 Chapter 2 Tolerance to environmental desiccation in moss sperm .....................................6 Chapter 3 Sex-specific volatile compounds influence microarthropod-mediated fertilization of moss……………………………………………………...……….…..37 Chapter 4 Community ecology of geothermal mosses: what drives diversity at temperature extremes?........................................................................................60 Chapter 5 Warming reduces the physiological barrier to reproductive success in Antarctic mosses…………………………………………………...........................................100 Chapter 6 Mosscosms: A classroom activity to encourage ecosystem-level thinking.............................................................................................................138 Chapter 7 Discussion…………………………………………………………………………….177 References.........................................................................................................199 vii Appendices Appendices List of Tables and Figures...........................................................228 Appendix A Supplemental materials to Chapter 3: Sex-specific volatile compounds influence microarthropod-mediated fertilization