The Riddle of the Sphinx: Population Ecology of the Endangered Blackburnʻs Sphinx Moth, Manduca Blackburni (Lepidoptera: Sphingidae) on an Invasive Host Plant
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The Riddle of the Sphinx: Population Ecology of the Endangered Blackburnʻs Sphinx Moth, Manduca blackburni (Lepidoptera: Sphingidae) on an Invasive Host Plant. A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAIʻI AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN ENTOMOLOGY (ECOLOGY, EVOLUTION, AND CONSERVATION BIOLOGY) DECEMBER 2019 By: Christine H. Elliott Thesis Committee: Dr. Daniel Rubinoff, Committee Chair Dr. William Haines Dr. Mark Wright Keywords: Blackburn’s sphinx moth, Manduca blackburni, relative abundance, ecological life table, oviposition DEDICATION This thesis is dedicated to my family: my two beautiful boys, Jacob and Phineas; my loving and supportive husband, Tim; and my Spartan mother, Barbara. Without your encouragement and support this could never have happened. I love you, I love you, I just love you! ACKNOWLEDGEMENTS This thesis was completed with tremendous support and assistance from my committee. Three years ago, Dr. Daniel Rubinoff was willing to take a risk and hire me. I will never be able to accurately convey my gratitude for this opportunity. Additionally, his clarity of thought and purpose was a trenchant force in keeping this work focused and on track. I also have tremendous appreciation for the vast knowledge and gentle expertise of Dr. William Haines. His generosity in time, editing, and advice was critical to my research and this thesis. Last but not least, Dr. Mark Wright was an invaluable sounding board and resource throughout my time, for which I am deeply grateful. His statistical guidance prevented my work from going off the rails and his eloquence under pressure has enriched my idiolect. In addition to my committee members, my research was greatly facilitated by Cynthia King and Dr. Elliott Parsons. Without their assitance and generous support this would have been an impossible task. My work was abetted by their excellent advice, kind guidance, and often physical labor! On that same note, I was assisted in the field by numerous volunteers who often joined me month after month and year after year. Avalon and Travis Paradea, Yvonne Garzon, Bob Kaufman, Lance Tanino, Jamie Tanino, Phil Hester, Bob Krause, Louise Hanna, Chuck Chimera, and many many others were incredibly generous with their time and will always hold a special place in my heart. However, I would have been figuratively and literally lost without the aid, good humor, and deep knowledge of Bob Okawa. He has been the most staunch, supportive, munificent, and entertaining volunteer I have ever had the great good fortune to know and in me he will have a fan for life! My fellow PEPS graduate students were a constant source of inspiration and enjoyment and I owe them many thanks. I am particularly grateful for Mason Russo and Priscilla Seabourn. They were both, in their own ways, inspirational and instrumental to my work. I am also grateful for the PEPS department office staff who assisted with all the planning and paperwork required for my research travel. Enough good things cannot be said about the efficiency, professionalism, and patience of Michelle Mililani Isaacs, Rachel Baltero, and Lu Yi Chun. I would also like to thank my lab-mates, Jared Bernard, Mitchel Logan, and Bradley Reil for all of their assistance, including, but not limited to, moral support, engaging conversations, editing, course advice, and field assistance all while managing their own busy schedules. i Drs. Camiel Doorenweerd and Michael San Jose have, likewise, been incredibly generous with their time, excellent ideas, and humor, and I am grateful to have been able to work with them both. I am indebted to Daniel Nitta for his inexhaustible patience and expertise with molecular work and recalcitrant DNA. I also owe so much to Dr. Conrad Gillett, who was the best fieldwork partner anyone could ever hope for. I cannot possibly thank him enough for his uncomplaining assitance, cracking advice, and delightful company. He has been instrumental to much of my growth as a scientist. Lastly, this thesis would not have been possible without funding provided by U.S. Fish and Wildlife Service, Pacific Islands Coastal Program and the Hawaii Department of Land and Natural Resources, Division of Forestry and Wildlife. Additional support came from the Tanada Family Entomology Award and the Wallace Mitchell Entomology Award. ii ABSTRACT Blackburnʻs sphinx moth, Manduca blackburni (Lepidoptera: Sphingidae; Butler 1880), is a large sphinx moth endemic to the Hawaiian Islands. In 2000, it became the second moth and the first Hawaiian insect to be federally listed as an endangered species, yet little was known about its population biology. Its primary host plant is the invasive weed tree tobacco, Nicotiana glauca (Solanaceae). Despite the presence of tree tobacco on six of the seven main Hawaiian Islands, Blackburn’s sphinx moth is currently known from only Maui, Kahoʻolawe, and Hawaiʻi Island where it occurs at densities well below what its invasive host plant would seem to support. In order to facilitate conservation efforts, I set out to analyze changes and patterns in abundance, elucidate ovipositional preferences, and identify the factors responsible for the apparent population suppression of this charismatic Hawaiian moth all on its novel invasive host plant. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................................. i ABSTRACT ................................................................................................................................... iii LIST OF TABLES ......................................................................................................................... vi LIST OF FIGURES ...................................................................................................................... vii CHAPTER 1. MONITORING RELATIVE ABUNDANCE USING IMMATURE LIFE STAGES: IMPLICATIONS FOR CONSERVATION AND MANAGEMENT ....................... 1 Introduction ............................................................................................................... 1 Methods ..................................................................................................................... 3 Study Sites ..................................................................................................... 3 Survey Methods .............................................................................................. 4 Statistical Analysis ......................................................................................... 6 Results ... ................................................................................................................... 6 Discussion . ............................................................................................................. 10 Management Recommendations .................................................................... 11 CHAPTER 2. OVIPOSITION PREFERENCES OF THE ENDANGERED BLACKBURN’S SPHINX MOTH (MANDUCA BLACKBURNI, LEPIDOPTERA: SPHINGIDAE) ON AN INVASIVE HOST PLANT ...........................................................................................................15 Introduction ........................................................................................................................15 Methods..............................................................................................................................17 Results .... ...........................................................................................................................18 Discussion ..........................................................................................................................22 CHAPTER 3. MORTALITY FACTORS OF THE ENDANGERED HAWAIIAN SPHINX MOTH, MANDUCA BLACKBURNI (SPHINGIDAE: LEPIDOPTERA) ON AN INVASIVE HOST PLANT, NICOTIANA GLAUCA (SOLANACEAE) ..........................................................27 Introduction .................................................................................................................27 Methods..............................................................................................................................29 Survey Sites ............................................................................................................29 Field Cohort Study .................................................................................................30 Partial Life Table Construction .............................................................................31 iv Marginal Attack Rates ...........................................................................................31 Results ................................................................................................................................32 Discussion ..........................................................................................................................34 WORKS CITED.............................................................................................................................38 v LIST OF TABLES Table 1.1. Transects surveyed by date and mean search coverage ( SEM) for host plants within transects............................................................................................................................................6 Table 1.2. Counts of viable and non-viable M. blackburni eggs by survey year...........................10 Table