PLANT NECTAR CONTRIBUTES TO THE SURVIVAL, ACTIVITY, GROWTH, AND FECUNDITY OF THE NECTAR-FEEDING WANDERING SPIDER CHEIRACANTHIUM INCLUSUM (HENTZ) (ARANEAE: MITURGIDAE) DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Robin M. Taylor, B.A, M.A. ***** The Ohio State University 2004 Dissertation Committee: Approved by Dr. Richard A. Bradley, Advisor Dr. Thomas E. Hetherington _____________________________ Dr. W. Mitch Masters Advisor Department of Evolution, Ecology, and Organismal Biology ABSTRACT Spiders are valued for their predation of insect pests, and, evaluated as an “assemblage” of species that employ different predatory strategies, constitute a natural biological control, particularly in agricultural crops. Spiders are obligate carnivores, requiring prey for normal growth, development, and reproduction. Because biologists have worked under the assumption that spiders are exclusively carnivorous, studies of the ecology of spiders and their acquisition and allocation of energy have assumed that prey is the single object of any spider’s foraging. The discovery in 1984 that orb-weaving spiderlings benefited nutritionally from pollen grains incidentally trapped by their webs, which they eat and recycle, was noteworthy. Growing evidence indicates that a large group of spiders may routinely exploit another plant-based food source: plant nectar. Observations of nectar feeding have been reported among crab spiders (Thomisidae), jumping spiders (Salticidae), and running spiders (Anyphaenidae, Clubionidae, and Corinnidae), all non-webbuilding wanderers that occupy vegetation. Spiders have the capacity to detect and digest plant nectar, and spiders that wander in vegetation are able to encounter nectar. Lab experiments show that newly-emerged, prey-deprived spiders live longer if they are provided with sucrose, a nectar proxy. My laboratory experiments show that plant nectar contributed ii significantly to the survival of newly-emerged Hibana velox Becker (Anyphaenidae), and to the survival, growth, activity, and fecundity, of Cheiracanthium inclusum (Hentz) (Miturgidae, formerly in Clubionidae). Both are highly active nocturnal running (also called “sac”) spiders. Experiments with C. inclusum measuring nighttime activity, and measuring the effects of adding plant nectar to varying levels of prey, the eggs of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), suggest that the simple sugars of plant nectar fuel the spider’s energetic activity, allowing the nutritional benefits of prey to be allocated to growth and reproduction. Spiders receiving a marginal amount of prey, for example, were able to mature and reproduce only if they also received plant nectar. During two successive growing seasons, nearly one third, and one quarter (respectively) of wandering spiders sampled from nectar-producing cotton plants tested positive for fructose, a plant-derived sugar. Pilot studies also showed increased survival and molting in C. inclusum provided with honeydew. iii ACKNOWLEDGMENTS I give heartfelt thanks to my advisor, Dr. Richard Bradley, for his unwavering enthusiastic support and for giving me free rein to pursue this project. I am indebted to Dr. Woodbridge Foster and his students for invaluable lab and bench space, materials, and lively lab discussions. I am grateful to George Keeney, Joan Leonard, Barb Shardy, and Traci Solli for generously sharing their time and resources; the BPL library staff for their incomparable helpfulness and competence; Cathy Drake for her cheerful steadfastness and knowledge, Rosie Ruiz for sharing spiders, and Frank de la Fuente for his extraordinary dedication to the lab. I thank Dr. Walker Jones, director of the Weslaco, Texas USDA-BIRU (Beneficial Insects Research Unit) for allowing me to work there. Dr. Robert Pfannenstiel’s painstaking work for the BIRU studying spider egg- feeding married perfectly with my own, and I am most grateful to him for generously sharing unpublished data, making Chapter 3 possible. Bob and the entire unit kindly provided space, materials (including the labs of Dr. Gary Elzen for moth eggs and Dr. Jesse deLeon for microtools), access to crops, and a work atmosphere as sunny as south Texas itself. The Wolfe lab (OSU) kindly provided equipment that I could not have afforded otherwise and that cut my work time and made it safer. Dr. David Bradley provided statistical advice and insights. Finally, with fond respect and admiration, I iv thank the other members of my committee, Drs. Thomas Hetherington and W. Mitch Masters, for their close and careful scrutiny of my dissertation draft. I am amazed by the time and care that they took and grateful for the final product. I appreciate both of these scholars and gentlemen more than they know. Funding for this work has been provided by Sigma Xi, AAS (American Arachnology Society), and OSU’s GRRA (Graduate Alumni Grants for Graduate Research and Scholarship). A Presidential Fellowship from OSU supporting my final year of dissertation preparation absolved me of teaching duties and allowed me to write full time, for which I am grateful beyond words. v VITA August 8, 1955 Born - Euclid, Ohio 1983 B.A. English, Ohio State University 1986 M.A. English, Ohio State University 1990–1997 Science writer, General Biology Program, Ohio State University Ohio Sea Grant College Program 1997–present Graduate Teaching Associate, The Ohio State University PUBLICATIONS Research Publication 1. Taylor R.M. & W. A. Foster. 1996. Spider nectarivory. American Entomologist, (Summer) 82–86. FIELDS OF STUDY Major Field: Evolution, Ecology, and Organsimal Biology vi TABLE OF CONTENTS Page Abstract............................................................................................................................ii Acknowledgments............................................................................................................iv Vita...................................................................................................................................vi List of Figures..................................................................................................................viii List of Tables ...................................................................................................................xi Chapters: 1. Spider Nectarivory: A Recently Recognized Phenomenon ............................1 References.......................................................................................................14 2. The benefits of extrafloral nectar to the survival of Hibana velox Becker (Araneae: Anyphaenidae) and to the survival, growth, and activity of Cheiracanthium inclusum (Hentz) (Araneae: Miturgidae), two nocturnal running spiders................................................................................................19 2.1 Abstract ....................................................................................................19 2.2 Introduction..............................................................................................20 2.3 Materials and Methods.............................................................................22 2.4 Results......................................................................................................25 2.5 Discussion ................................................................................................30 References.......................................................................................................40 3. The effects of adding plant nectar to four levels of protein on the life history of the running spider Cheiracanthium inclusum .................................................45 3.1 Abstract ....................................................................................................45 3.2 Introduction..............................................................................................46 3.3 Materials and Methods.............................................................................48 3.3.1 Containers and diets for immatures ..........................................48 3.3.2 Containers and diets for reproductive females..........................50 3.4 Results......................................................................................................52 3.4.1 Effects of nectar on survival, growth, and maturation..............52 3.4.2 Effects of nectar on functional maturity and reproductive competence..........................................................................................52 3.4.3 Effects of nectar on body size and fecundity ............................53 3.4.4 Post hoc analysis.......................................................................55 vii 3.4.5 Offspring robustness .................................................................56 3.5 Discussion ................................................................................................56 References.......................................................................................................66 4. Nectar feeding as a common occurrence among wandering spiders: Evidence from a Texas cotton crop.................................................................................72 4.1 Abstract ....................................................................................................72 4.2 Introduction..............................................................................................73