Evolution and Phylogeography of New World Gastropod Faunas
Total Page：16
File Type：pdf, Size：1020Kb
Evolution and Phylogeography of New World Gastropod Faunas by Warren Brian Simison B.A. (University of California, San Diego) 1985 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Integrative Biology in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, BERKELEY Committee in charge: Professor David R. Lindberg, Chair Professor Brent D. Mishler Professor John W. Taylor Spring 2000 The dissertation of Warren Brian Simison is approved: Chair Date Date Date University of California, Berkeley Spring 2000 Evolution and Phylogeography of New World Gastropod Faunas Copyright 2000 by Warren Brian Simison Abstract Evolution and Phylogeography of New World Gastropod Faunas by Warren Brian Simison Doctor of Philosophy in Integrative Biology University of California, Berkeley Professor David R. Lindberg, Chair This dissertation covers a broad range of evolutionary topics, but its primary focus is on the use of molecular phylogenetics to reconstruct phyletic relationships and biogeography of gastropod molluscs, and in particular, the clade Patellogastropoda. The first chapter tests the long held view that the Gulf of California, Mexico is an isolated basin and as such behaves as an island having insular effects on gastropod evolution. Tests are performed that compare the level of endemicity in the Gulf to the surrounding eastern Pacific fauna. The remaining four chapters apply molecular phylogenetics to specific biological methodologies and questions. Chapter 2 examines the combinability of 16S and COI mitochondrial genes in a phylogenetics analysis of New World Patellogastropoda and presents a robust phylogenetic hypothesis. In chapter 3 molecular and morphological techniques are used to resolve a putative cryptic species complex, while in chapter 4, the patellogastropod phylogeny is used in conjunction with an innovative collecting methodology to clarify a long-standing confusion surrounding the identity of several northeast Pacifc patellogastropods. 1 This includes the discovery of a new species in the Gulf of California. Lastly, chapter 5 uses a molecular phylogeny to examine the biogeography of the New World patellogastropods and generates testable biogeographical hypotheses for the northeast Pacific, Chilean, and tropical New World faunas. These hypotheses are unified by a global hypothesis that ties the evolutionary history of these patellogastropod faunas to a western Tethyan origin. 2 Table of Contents Introduction ii Acknowledgments v Chapter One: A New View of the Gulf of California Text 1 Tables and Figures 25 Literature Cited 40 Chapter Two: Data Compatibility and Evolutionary Relationships of New World Patellogastropods Text 43 Tables and Figures 89 Literature Cited 107 Chapter Three: Morphological and Molecular Resolution of a Putative Cryptic Species Complex: A Case Study of Notoacmea fascicularis (Gastropoda: Patellogastropoda) Text 111 Tables and Figures 128 Literature Cited 135 Chapter Four: On the Identity of Lottia strigatella (Carpenter, 1864) (Patellogastropoda:Lottidae) Text 139 Tables and Figures 167 Literature Cited 174 Chapter Five: Phylogeographical patterns of New World Patellogastropoda Text 178 Tables and Figures 193 Literature Cited 201 i Introduction This dissertation is composed of five chapters, each focused on the evolutionary history of near shore gastropods. The first chapter examines the hypothesis that the Gulf of California is an isolated body of water and as such behaves as an island having insular effect on gastropod evolution. In support of this hypothesis, there have been many claims that the Gulf of California is a repository for endemics of many taxa. Chapter one tests whether the level of endemism in the Gulf of California differs from that of the rest of the tropical eastern Pacific continental shelf. Using a “window” analysis of a new gastropod database containing the ranges of over 2,400 tropical eastern Pacific species does this. The “window” analysis examines the number of species ranges restricted to fixed lengths of coastline (the “window”). As the “window” is incrementally shifted along the eastern Pacific coastline, the percentage of ranges restricted to each window increment is tallied. This produces a coastal profile of the level of endemism for a particular “window” size. One of the “windows” is equal to the total coastal length of the Gulf of California, thereby permitting a comparison of the level of endemicity in the Gulf of California to the rest of the tropical eastern Pacific. The remaining chapters (2-5) focus on the evolutionary history and phylogeography of the New World Patellogastropoda. The Patellogastropda are an ideal study group for phylogeography because they primarily occupy the near shore rocky intertidal of every New World coastline, which permits their ii evolutionary history to be correlated with the geological history of the New World continental margins. Chapter 2 is a phylogenetic analysis of New World Patellogastropoda and an analysis of the compatibility of the two molecular data sets employed to infer Patellogastropoda phylogeny. The mitochondrial markers for the large subunit ribosomal RNA gene (16S) and Cytochrome c Oxidase subunit I (COI) were employed for the analysis. Only 31 of the OTUs were successfully sequenced for COI resulting in an uneven sampling between 16S (57 OTUs) and COI (31 OTUs) data. Many tests were performed to determine whether these two sources of molecular data were compatible in a combined phylogenetic analysis. In addition to testing for uneven sample size, the compatibility of informative phylogenetic content was also examined. The results suggested that 16S and COI are both phylogenetically informative, but at different phylogenetic levels. COI was more informative for more recent evolutionary events while 16S was better at resolving deeper events and when combined in a single analysis produced poorly supported hypotheses incompatible with biogeographical distributions. The results from chapter 2 were used to examine specific biological topics within the evolutionary history of patellogastropods, three of which are included as chapters 3, 4, and 5. In chapter 3 variation found in COI was used to examine the validity of a morphological cryptic species complex. It had been suggested that Notoacmea fascicularis was a complex of two species based on difference in radular morphology. Radular morphology has been the primary diagnostic feature in the systematization of gastropods for over two centuries. However the iii recent availability of techniques, which enable the sequencing of DNA has broadened our ability to accurately reconstruct the evolutionary history of life. These techniques were used to examine the possibility that N. fascicularis is a cryptic species complex. Chapter 4 describes a collecting methodology that suggests that the current taxonomy of living gastropod groups is seriously flawed. The more organisms that are collected and sequenced, the more it becomes apparent that the current nomenclature for patellogastropods is incomplete and misleading. Therefore, I adopted a collecting strategy that intentional avoided all preconceived notions of taxonomic assignment. Instead, collections were made and the slightest variation in morphology and habitat were sampled. The objective of this strategy was to build a large database of molecular sequences from many different habitats and localities and be able to discover misnamed and unnamed species. In chapter 4, a molecular phylogeny based on my collecting strategy reveals several species of limpets formerly believed to be a single wide ranging species (Lottia strigatella), one of which was undescribed until now. Chapter 5, the final chapter, describes six biogeographical patterns observed for New World patellogastropods and presents hypotheses for the origins of these patterns. The biogeographical patterns were discovered by mapping the localities of the specimens onto a complete 16S New World patellogastropod phylogeny. The chapter is concluded with a global hypothesis synthesizing all of the biogeographical hypotheses into a single testable biogeographical hypothesis. iv Acknowledgements I owe a great deal of gratitude to the many individuals who have helped me pursue my interests in evolutionary biology. I am particularly grateful to my advisor, David Lindberg, for believing in me and giving me the rare opportunity to pursue a career in academia. Lindberg has always provided the necessary resources for my research: If I needed a digital camera, a computer, a computer program, ESEM training, sequencing supplies, or anything, he made sure that I had whatever I needed for my research. I am also thankful to my lab mates, Rob Guralnick, Ross Nehm, Marta deMaintenon, Alicia Cordero, Kirsten Lindstrom, Jim Kurpius, Emina Begovic, and Paul Bunje. All have been wonderful lab mates, have helped me in many ways, and have put up with my occasional mood swings. I also owe a special thanks to some of the post-docs whom I have had the privilege to work with: Charlie Wray spent many patient hours training Chris Meyer and me the temperamental art of manual DNA sequencing; Klaus Hedegård taught me much about gastropod shell morphology and always kept me on my toes. Sharon Lynch generously helped me with cloning techniques and general molecular knowledge. Whether they knew it or not, Allen Collins and Chris Meyer were my graduate student mentors. We spent many hours together learning DNA sequencing, SCUBA diving, and