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Genetic and Morphological Variation in Taeniatherum Caput

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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Boise State University - ScholarWorks GENETIC AND MORPHOLOGICAL VARIATION IN TAENIATHERUM CAPUT- MEDUSAE (MEDUSAHEAD): TAXOMONIC DIVERSITY, GEOGRAPHIC ORIGINS, MULTIPLE INTRODUCTIONS AND FOUNDER EFFECTS by Morgan Lindsey Peters A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Biology Boise State University August 2013 © 2013 Morgan Lindsey Peters ALL RIGHTS RESERVED BOISE STATE UNIVERSITY GRADUATE COLLEGE DEFENSE COMMITTEE AND FINAL READING APPROVALS of the thesis submitted by Morgan Lindsey Peters Thesis Title: Genetic and morphological variation in Taeniatherum caput-medusae (Medusahead): taxonomic diversity, geographic origins, multiple introductions and founder effects Date of Final Oral Examination: 19 May 2011 The following individuals read and discussed the thesis submitted by student Morgan Lindsey Peters, and they evaluated her presentation and response to questions during the final oral examination. They found that the student passed the final oral examination. Stephen J. Novak, Ph.D. Chair, Supervisory Committee James F. Smith, Ph.D. Member, Supervisory Committee Marcelo Serpe, Ph.D. Member, Supervisory Committee René Sforza, Ph.D. Member, Supervisory Committee The final reading approval of the thesis was granted by Steven J. Novak, Ph.D., Chair of the Supervisory Committee. The thesis was approved for the Graduate College by John R. Pelton, Ph.D., Dean of the Graduate College. DEDICATION This thesis is dedicated with love to Jeannette Irene Turman (1926-2011) and Paul Onil Frechette (1923-2011). iv ACKNOWLEDGEMENTS This thesis would not have been possible without the endless patience, guidance, and enthusiasm of my major advisor Dr. Stephen J. Novak. I am grateful to have had such an intelligent and passionate mentor and could not have asked for better. I would also like to express my deepest gratitude to Dr. James F. Smith for his unwavering support and encouragement and Dr. Marcelo Serpe for his helpful comments. I am also indebted to Dr. René Sforza for his many hours in the field collecting samples for this project and his insightful comments. This collaborative project would not have been possible without him. I also want to thank Yves Tindón and Vivian Zapata for their enthusiasm and help in the lab while working on this thesis. It is also a sincere pleasure to acknowledge those individuals who made my time at Boise State a memorable experience. In particular, the love and support of my friends and colleagues: Lacie Schulte, Emma Wilson, Allison Korte, Kevin (Gus) Gluckert, and Michael Davis(.com). I would also like to extend a special thank you to my loving family and my partner, Erik Hinkle, for their continuous support during my graduate career. This acknowledgement section would not be complete without a thank you to the Bar Gernika Evolution Group for many a Friday night spent in engaging conversations over tasty adult beverages. Finally, thanks to all of the organizations that contributed funding to this research: the United States Department of Agriculture, National Institute of Food and Agriculture v (USDA NIFA), Project Number IDAR-2008-03063; Boise State University and the United States Department of Agriculture European Biological Control Laboratory. vi ABSTRACT Invasive species are novel to a region, thus their timely and accurate identification is a critical first step in recognizing and managing the threats that they may present in their new habitats. Accurate identification of an introduced species in its new range can prove difficult however for a species that displays taxonomic complexity in its native range, i.e. consists of multiple, morphologically similar subspecies. Across its native range, Taeniatherum caput-medusae (medusahead) exhibits taxonomic complexity. Three subspecies have been recognized: T. caput- medusae ssp. caput-medusae, T. caput-medusae ssp.asperum, and T. caput- medusae ssp. crinitum. While subspecies caput-medusae is found in the western Mediterranean and subspecies crinitum occurs from eastern Europe to Central Asia, subspecies asperum is distributed across the geographic distribution of the species. Only subspecies asperum is believe to occur in the United States, where it is now invasive in portions of California, Idaho, Nevada, Oregon, Utah, and Washington. As part of ongoing research to better understand and manage this invasion, genetic analyses of both native and invasive populations of medusahead were conducted. An important prerequisite to these analyses is the proper identification of the three subspecies. In the current study, plants from each native population were grown in a greenhouse common garden, harvested at maturity, and measured using previously described morphological characters. After Bonferroni correction, three characters, glume length, glume angle, and vii palea length, were found to be statistically significant. Thus, these three characters were quite useful in assigning plants to each of the three subspecies. I found that two other characters, lemma hairs and conical cells, were less informative. Differentiation among native populations of medusahead was further assessed using a molecular genetic marker. The results of a UPGMA cluster diagram based on allozyme data indicates that subspecies crinitum is genetically differentiated from the other two, some populations of subspecies caput-medusae and asperum co-occur within different clusters, and subspecies asperum is the most variable. Results of the analysis of multilocus genotypes are generally consistent with the UPGMA diagram (e.g., subspecies caput- medusae and asperum share six multilocus genotypes). This research confirms the need of such studies to disentangle the taxonomic complexity that can be found in the native range of invasive species. The results of an earlier allozyme analysis were consistent with the genetic signature associated with multiple introductions, although this finding can only be confirmed with the analysis of native populations. In the current study, I compared allozyme diversity in native and invasive populations of medusahead to: identify the geographic origin(s) for the U.S. invasion, test the multiple introduction hypothesis, and determine the genetic consequences of these events. Five of the seven homozygous multilocus genotypes previously observed in the western U.S. have been detected in native populations. The geographic origins for these introductions appear to have been drawn from France, Sardinia, Greece, and Turkey, although additional analyses are ongoing. These findings provide support for the multiple introduction hypothesis. Results of this study have implications for the biological control of viii medusahead: i) the search for effective and specific biological control agents will have to occur broadly across the species’ native range, ii) multiple agents may be required to control invasive populations that are admixtures, and iii) because invasive population are genetically depauperate, highly adapted biocontrol agents are likely to be quite effective. ix TABLE OF CONTENTS DEDICATION ......................................................................................................................... iv ACKNOWLEDGEMENTS ...................................................................................................... v ABSTRACT ............................................................................................................................ vii LIST OF TABLES ................................................................................................................. xiii LIST OF FIGURES ................................................................................................................ xv CHAPTER 1: MORPHOLOGICAL AND GENETIC DIFFERENTIATION AMONG SUBSPECIES OF TAENIATHERUM CAPUT-MEDUSAE (MEDUSAHEAD; POACEAE): DISENTANGLING TAXONOMIC COMPLEXITY IN THE NATIVE RANGE ..................................................................................................................................... 1 Abstract ......................................................................................................................... 1 Introduction ................................................................................................................... 3 Materials and Methods .................................................................................................. 7 Plant Collection ................................................................................................. 7 Greenhouse Common Garden ........................................................................... 9 Morphological Measurements .......................................................................... 9 Enzyme Electrophoresis.................................................................................. 10 Data Analysis .................................................................................................. 11 Results ......................................................................................................................... 13 Morphological Traits and Variation Among Subspecies ................................ 13 Genetic Diversity ............................................................................................ 14 Multilocus Genotypes ..................................................................................... 15 x Genetic Relationships
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