REPRODUCTIVE ECOLOGY OF A RARE SERPENTINE ENDEMIC, VANCOUVERIA CHRYSANTHA (BERBERIDACEAE) By Brian Dykstra A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Biology Committee Membership Dr. Michael R. Mesler, Committee Chair Dr. Erik S. Jules, Committee Member Dr. Alexandru M.F. Tomescu, Committee Member Dr. Jeffrey White, Committee Member Dr. Michael R. Mesler, Graduate Coordinator July 2014 ABSTRACT REPRODUCTIVE ECOLOGY OF A RARE SERPENTINE ENDEMIC, VANCOUVERIA CHRYSANTHA (BERBERIDACEAE) Brian Dykstra This study examined how pollinator visitation and local neighborhood density may affect pollen limitation (PL) of reproductive success for Vancouveria chrysantha Greene (Berberidaceae), a rare plant, strictly endemic to serpentine substrates in northwestern California and southwestern Oregon. Previous to this study nothing was known about its pollination biology. V. chrysantha is protandrous, self-incompatible, and presents pollen and nectar attractive to pollinators. Although infrequently seen, bumblebees were the most common floral visitor, and were the only visitor observed contacting receptive stigmas. The majority of individual plants studied experienced PL, and average supplemental-pollination seed set was nearly double that of natural open- pollination. Surprisingly, bumblebee visitation did not predict the degree of PL, suggesting that the amount or quality of pollen carried by bumblebees is more important than their rate of visitation. Increases is the number of neighbors at the largest spatial scale measured (25 m) significantly decreased PL, but the smallest scale (1 m) had no effect, indicating that near neighbors may not donate quality pollen, and larger spatial scales are more likely to encompass suitable pollen donors. The dependence of V. chrysantha on bumblebees and local neighborhoods large enough to harbor compatible mates has implications for the conservation and management of this rare plant; decreases in plant or bee abundance could negatively affect population persistence. ii ACKNOWLEDGEMENTS I am grateful and in debt to many people who contributed to the development, implementation, and completion of this research project. Many thanks go to Dr. Michael Mesler, my advisor and instructor, for his encouragement, and for providing a great opportunity to research pollination biology under his guidance. Best wishes and many thanks to those who assisted me in the field, contributing much sweat and patience: Danielle Cummins, Shannon Davis, Edde Dula, Sasan Hariri-Moghadam, Laurel Hoffman, Rhianna Jones, Jian Kang, George Meindl, Samuel O’Dell, Hillary Ronney, Bobby Shearer, Glenn Shelton, and Kelly. Thank you to those who provided location information, especially Lisa Hoover, Scott Loring, and Steven Darrington. Thanks also go to Abbie Jossie, Erin Brandy, and Robin Taylor Davenport of the Medford District BLM and everyone else in Oregon who helped. Also thank you to my family for providing support. Thank You Shannon, Ruby and Poplyn! Funding was provided by a Humboldt State University Masters Grant. Thank you to all! I dedicate this work to Jian Kang, whose sense of adventure, humor, and hard work ethic lightened my spirits in the field. – iii TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iii TABLE OF CONTENTS ................................................................................................... iv TABLE OF FIGURES ....................................................................................................... vi INTRODUCTION .............................................................................................................. 1 MATERIALS AND METHODS ........................................................................................ 3 Study Species .................................................................................................................. 3 Study Site ........................................................................................................................ 7 Breeding System and Floral Biology .............................................................................. 9 Focal Plants ................................................................................................................... 10 Insect Visitation ............................................................................................................ 11 Pollen Limitation .......................................................................................................... 11 Neighborhood Density .................................................................................................. 15 Data Analysis ................................................................................................................ 15 RESULTS ......................................................................................................................... 19 Breeding System and Floral Biology ............................................................................ 19 Insect Visitation ............................................................................................................ 26 Pollen Limitation .......................................................................................................... 37 DISCUSSION ................................................................................................................... 44 Breeding System and Floral Biology ............................................................................ 44 Insect Visitation ............................................................................................................ 45 iv Pollen Limitation .......................................................................................................... 47 Implications for Conservation ...................................................................................... 48 LITERATURE CITED ..................................................................................................... 52 v TABLE OF FIGURES FIGURE 1. FORTY-THREE RECORDED LOCATIONS OF V. CHRYSANTHA IN OREGON, BASED ON HERBARIUM SPECIMENS AND FIELD OBSERVATIONS (OREGON FLORA PROJECT 2013). DIAMONDS ARE OBSERVATIONS, LARGER CIRCLES INDICATE CLUSTERED RECORDS. ..... 5 FIGURE 2. FORTY-THREE RECORDED LOCATIONS OF V. CHRYSANTHA IN CALIFORNIA, BASED ON HERBARIUM SPECIMENS AND FIELD OBSERVATIONS (CALFLORA 2013). .................. 6 FIGURE 3. MAP OF APPROXIMATE STUDY AREA LOCATION. UTM ZONE 10, 436903 E, 4653464 N. CREATED WITH HTTP://WWW.GMAPGIS.COM/ ............................................ 8 FIGURE 4. LANDSCAPE OF THE STUDY AREA........................................................................ 8 FIGURE 5. FRUITS MANUALLY OPENED FOR OVULE AND SEED COUNTS. (A) A FRUIT WITH SEVERAL UNDEVELOPED OVULES (ARROW 1) AND ONE SEED (ARROW 2). (B) A FRUIT WHERE ALL 11 OVULES DEVELOPED INTO SEEDS. ........................................................ 13 FIGURE 6. DEHISCED FRUIT WITH SEEDS EXPOSED TO DISPERSAL VECTORS. ...................... 14 FIGURE 7. EARLY ANTHESIS. THE ANTHERS ARE UNDEHISCED (ARROW 1), THE PETALS (ARROW 2) AND SEPALS (ARROW 3) BEGIN TO REFLEX. ............................................... 21 FIGURE 8 (A AND B). TWO EXAMPLES OF STAMINATE PHASE FLOWERS. PETALS ARE PRODUCING NECTAR IN THEIR HOOD-SHAPED POUCHES (ARROW 1) AND ANTHERS HAVE DEHISCED, WITH POLLEN AMASSED AT TIP (ARROW 2). ................................................ 22 FIGURE 9. THREE CARPELLATE PHASE FLOWERS. PETALS SECRETE NECTAR (ARROW 1). THE STYLE EXTENDS BEYOND THE ANDROECIUM, AND EXPOSES A STICKY STIGMA vi (ARROW 2). IN THIS PHASE THE ANDROECIUM REMAINS FIRMLY ATTACHED, AND IS GRASPED BY BUMBLEBEES WHEN THEY COLLECT NECTAR. ......................................... 23 FIGURE 10. AUTO-POLLINATION. UNVISITED CARPELLATE PHASE FLOWERS (A, TENTED PLANT; B, FOCAL PLANT). THE POLLEN MASS AT TIP OF THE ANDROECIUM REMAINS LARGELY INTACT (ARROW 1) BUT SOME POLLEN HAS BEEN DEPOSITED ON THE STIGMA AS THE RESULT OF STYLE ELONGATION (ARROW 2). .................................................... 24 FIGURE 11. FLORAL SENESCENCE. BY THIS STAGE, SOME SEPALS AND PETALS HAVE FALLEN (ARROW 1), THE ENLARGED STIGMA IS COVERED WITH POLLEN GRAINS (ARROW 2), AND THE ANDROECIUM HAS ABSCISED (ARROW 3). ................................................ 25 FIGURE 12. PROPORTION OF DIFFERENT TYPES OF INSECTS VISITING FOCAL PLANTS IN 2010. BUMBLEBEES MADE 23 FOCAL PLANT VISITS; SMALL SOLITARY BEES MADE 4. FLIES, ANTS, AND BEETLES EACH MADE ONLY 1 FOCAL PLANT VISIT. N = 30 VISITS TO FOCAL PLANTS. ....................................................................................................................... 28 FIGURE 13. CONCURRENT POLLEN AND NECTAR COLLECTION BEHAVIOR BY BOMBUS. ...... 29 FIGURE 14. BUMBLEBEE VISITS TO CARPELLATE PHASE FLOWERS (A, B, AND D) AND A STAMINATE PHASE FLOWER (C). BEES GRASP THE ANDROECIUM, AND MOVE AROUND THE FLOWER IN A CIRCULAR FASHION. THE VENTRAL ABDOMINAL SURFACES CONTACTED POLLEN (C) AND RECEPTIVE STIGMAS (A, B, AND D). ................................ 30 FIGURE 15. AN UNIDENTIFIED SMALL SOLITARY BEE VISITS A STAMINATE PHASE FLOWER IN 2009. THIS BEE DID COLLECT NECTAR BY OCCASIONALLY CLIMBING TO THE PETALS ABOVE. .......................................................................................................................