Body Size Evolution and Diversity of Fishes Using the Neotropical Cichlids (Cichlinae) As a Model System
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Body Size Evolution and Diversity of Fishes using the Neotropical Cichlids (Cichlinae) as a Model System by Sarah Elizabeth Steele A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Ecology and Evolutionary Biology University of Toronto © Copyright by Sarah Elizabeth Steele 2018 Body Size Evolution and Diversity of Fishes using the Neotropical Cichlids (Cichlinae) as a Model System Sarah Elizabeth Steele Doctor of Philosophy Department of Ecology and Evolutionary Biology University of Toronto 2018 Abstract The influence of body size on an organism’s physiology, morphology, ecology, and life history has been considered one of the most fundamental relationships in ecology and evolution. The ray-finned fishes are a highly diverse group of vertebrates. Yet, our understanding of diversification in this group is incomplete, and the role of body size in creating this diversity is largely unknown. I examined body size in Neotropical cichlids (Cichlinae) to elucidate the large- and small-scale factors affecting body size diversity and distribution, and how body size shapes species, morphological, and ecological diversity in fishes. Characterization of body size distributions across the phylogeny of Neotropical cichlids revealed considerable overlap in body size, particularly in intermediate-sized fishes, with few, species-poor lineages exhibiting extreme body size. Three potential peaks of adaptive evolution in body size were identified within Cichlinae. I found freshwater fishes globally tend to be smaller and their distributions more diverse and right-skewed than marine counterparts, irrespective of taxonomy and clade age, with a strengthening of these trends in riverine systems. Comparisons of Neotropical cichlid body size diversity and distribution to this broader context shows that body size patterns are largely abnormal compared to most freshwater fishes, particularly those of the Neotropics. ii This implies that small body size is rarer in Cichlinae, despite several independent cases of body size decrease in this lineage. I found that these small-bodied lineages are miniaturized cichlids, exhibiting strong reduction in body size, as well as paedomorphic characters and ontogenetic truncation compared to their sister taxa. Further examination of ontogenies across Neotropical cichlids found considerable shape conservatism over ontogeny and phylogeny, with cichlids following similar ontogenetic trajectories. Therefore, ontogenetic pathways do not contribute considerably to morphological divergence seen in adults, with divergence likely occurring in the larval stage or perhaps during embryology. The evolution of ontogeny, body size, and shape did not correspond to a unique adaptive peak in miniatures, or three body size optima predicted from the distribution of size across the phylogeny. Rather, it is complex and, like early trait divergence previously seen, diversifies early in the phylogeny across the major lineages of Neotropical cichlids. iii Acknowledgments Firstly, I would like to acknowledge my supervisor Hernán López-Fernández. He introduced me to a field of research I had little exposure to and a world within fishes I became deeply obsessed with exploring. I thank him for our many discussions about body size evolution and the room to expand my research as I developed an approach to tackling my research questions. He provided me with many opportunities in the field, at professional meetings, through workshops, and during our brainstorming sessions, to explore and learn in depth each aspect of my program. I appreciate his guidance and criticism through each stage of my thesis while allowing me to work independently. I have grown considerably as a researcher and thank him for our endless discussions of fish, evolution, and life. I would like to thank Nathan Lovejoy (University of Toronto - U of T) and David Evans (U of T) for serving on my supervisory committee and providing guidance and advice throughout my PhD. I would also like to thank Dean Adams (Iowa State University) and Sebastian Kvist (U of T) for serving as my external defense committee members and the suggestions provided. I would like to thank Helen Rodd (U of T) and D. Luke Mahler (U of T) for serving on my appraisal committee, and providing useful insight that has helped improve my research. I am very grateful for the personal and academic advice and support I have received from Deborah McLennan (U of T), Helen Rodd (U of T), Luke Mahler (U of T), and Sebastian Kvist (U of T) throughout my academic career. I am indebted to Mary Burridge, Erling Holm, Marg Zur, and Don Stacey for technical support with the Royal Ontario Museum (ROM) collection, outreach opportunities to communicate science to the public, the ability to maintain work on Canadian fishes, as well as the curatorial skills and knowledge I have gained. I extend a sincere thank you to Don Jackson (U of T) who has iv provided considerable guidance and support throughout my PhD, as well as helped shape my early academic career as the supervisor of my undergraduate honours thesis. My research was significantly improved due to the specimen contributions, methodological advice provided by several individuals, and funding sources. For access to additional specimens, I would like to thank Mark Sabaj Perez and Mariangeles Arce Hernandez (Academy of Natural Sciences of Drexel University); Kevin Conway and Heather Prestridge (Texas A&M University); Dean Hendrickson, Adam Cohen, and Melissa Casarez (University of Texas at Austin). For insightful discussions and considerable help with methods, I would like to thank Dean Adams (ISU), Michael Collyer (Chatham University), Antigoni Kaliontzopoulou (Research Centre in Biodiversity and Genetic Resources) for the opportunity to participate in the Introduction to Geometric Morphometrics in R workshop, Tromsø, Norway during the formative years of my PhD. I am very fortunate to have received funding for my research from NSERC (CGS M and PGS D), various fellowships/awards from the University of Toronto, the American Society of Ichthyologists and Herpetologists (Raney Award), and the American Cichlid Association (Guy Jordan Research Award). I am very grateful to Katriina Ilves (Pace University), Nathan Lujan, and Luke Frishkoff for valuable research and personal support regarding my career. I thank Nathan Lujan for the opportunity to collaborate and expand my research focus. I am indebted to my labmates Jessica Arbour, who has provided endless R support and methodological assistance, Frances Hauser and Viviana Astudillo-Clavijo, who have provided insightful comments on my thesis and moral support, and Stéphanie Lefebvre, who aided in shaping Chapter 2 data, many life lessons, and for her endless personal support throughout my PhD. I also thank my labmates Alejandro Londoño-Burbano, Sean Anderson, and Tom Morgan for advice, useful criticisms of my research, and for personal support. To my adopted lab member, Matt Kolmann, who has v provided considerable research and personal criticisms in the office, lab, and field, as well as support to help me grow as a person, I thank for all he put and helped me through. I especially thank Matt for our collaboration which expanded considerably to become Chapter 2 of my thesis. I would like to thank Collin VanBurren for our enlightened discussions about life, research, and evolutionary biology throughout my PhD. One such discussion about the assumptions of body size across fishes largely spurred Chapter 2. I owe many thanks to fellow graduate students James Boyko, Kentaro Chiba, Tom Cullen, Danielle DeCarle, Michael Foisy, Melanie Massey, Karma Nanglu, Ashley Reynolds, Santiago Sánchez-Ramírez, and Mateusz Wosik for significant guidance and support. I extend sincere appreciation to my friend Stacey Kerr, who has carried, dragged, and pushed me through the most difficult times and who has provided endless support through my undergraduate and graduate years. Most importantly, I would like to thank my mother Rosalie Steele who, despite our differences of opinion on fish, offered unconditional and continuous support throughout my PhD and my childhood. I owe much of what I am because of her strength and guidance throughout my life. I also owe many thanks to my father Kevin Mann, and brothers Ryan and Nolan Steele for support and helping me to have a respectable perspective on life. Finally, I would like to thank my partner Michael Swift who has helped me through many of the most challenging moments of my life, as well as stood by me as I continued to push myself and celebrated some of the most rewarding with me. vi Table of Contents Acknowledgments ...................................................................................................................iv Table of Contents ................................................................................................................... vii List of Tables ......................................................................................................................... xii List of Figures ........................................................................................................................xiv List of Appendices ............................................................................................................... xvii I. General Introduction.............................................................................................................. 1 I.1 Background ....................................................................................................................