THE ECOLOGY AND DISTRIBUTION PATTERNS OF A RARE SERPENTINE ENDEMIC, PACKERA LAYNEAE ____________ A Thesis Presented to the Faculty of California State University, Chico ____________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Botany ____________ by Melanie Suzanne Williams Summer 2014 ACKNOWLEDGEMENTS I would like to thank my committee, Dr. Colleen Hatfield, Dr. Kathy Gray, and Lawrence Janeway for their guidance, insight, and critique, and for providing motivation when it was most needed. Thank you to Erin Gottschalk Fisher, Tim Hanson, and Matt Simenc for their assistance in the field as well as their friendship and support. I would like to thank Melanie Gogol-Prokurat at California Department of Fish and Wildlife, Graciela Hinshaw at the Bureau of Land Management, and Kyle Merriam and Chris Christofferson at the National Forest Service, for sharing their experience with this species. A special thank you to Rob Schlising, Linnea Hanson, and Barb Castro for their interest and enthusiasm regarding this work. I would also like to thank my mom for instilling in me love and awe of the natural world, my dad for his persistent belief in me, and my sister for reminding me when I need it, what life is really about. Thank you to all of my family and friends for their love and encouragement. The greatest thank you to D.J., whose support has been above and beyond. This research was supported by the Jim Jokerst Field Botany Award, the Friends of the Chico State Herbarium, and by the Feather River Ranger District, Plumas National Forest. iii TABLE OF CONTENTS PAGE Acknowledgements.................................................................................................... iii List of Tables ............................................................................................................. vi List of Figures............................................................................................................ vii Abstract...................................................................................................................... viii CHAPTER I. Introduction................................................................................................. 1 II. Background................................................................................................. 30 Biodiversity Hotspots......................................................................... 14 Study Species..................................................................................... 15 Study Sites ......................................................................................... 17 III. Methods....................................................................................................... 22 Habitat Characterization .................................................................... 22 Plant Growth ...................................................................................... 23 Seed Dispersal.................................................................................... 23 Seed Viability..................................................................................... 25 Modeling............................................................................................ 30 Data Analysis..................................................................................... 34 IV. Results......................................................................................................... 59 Habitat Characterization .................................................................... 35 Plant Growth ...................................................................................... 38 Seed Dispersal.................................................................................... 41 Seed Viability..................................................................................... 41 Modeling............................................................................................ 43 V. Discussion................................................................................................... 45 iv PAGE Literature Cited .......................................................................................................... 57 v LIST OF TABLES TABLE PAGE 1. The Possible Combinations for Defining the Seven Types of Rarity ............. 2 2. Seed Germination Treatments and Replicates................................................. 30 3. P-values for each of the Analyzed Habitat Variables ..................................... 38 4. Plant Community Associated with P. layneae within Study Area Plots......... 39 5. Dispersal Distance and % of Total Seeds Recovered for each Category of Dispersal Distance in Dispersal Array Traps. ........................................... 41 6. Percent of P. layneae Seeds that Germinated and Persisted in Various Substrates................................................................................................... 42 vi LIST OF FIGURES FIGURE PAGE 1. Packera layneae populations and the distribution of serpentine and gabbro substrate in California ................................................................... 10 2. Packera layneae locations (Consortium of California Herbaria 2014) with Pine Hill complex and the distribution of serpentine and gabbro soils throughout the range of Packera layneae ............................. 12 3. Packera layneae inflorescences ...................................................................... 16 4. Location of the study sites: Upper and Lower Woodleaf, and Brownsville ............................................................................................... 18 5. Study Sites: Upper Woodleaf, Lower Woodleaf, and Brownsville ................ 20 6. Example of a seed dispersal array in field....................................................... 25 7. Average (±SE) percent canopy cover for P. layneae plots at each of the three study locations as well as on-patch (P. layneae present) vs. off-patch (P. layneae absent) at Upper Woodleaf.................. 36 8. Average (±SE) duff depth for P. layneae plots at each of the three study locations as well as on-patch (P. layneae present) vs. off-patch (P. layneae absent) at Upper Woodleaf..................................... 36 9. Average (±SE) slope for P. layneae plots at each of the three study locations as well as on-patch (P. layneae present) vs. off-patch (P. layneae absent) at Upper Woodleaf..................................... 37 10. Average plant sizes comparing an early (possibly first) year’s size to the sequential year’s size, for young P. layneae plants ................. 40 11. Maxent output based on background layers of annual precipitation and maximum temperature, restricted to serpentine and gabbro soils in Yuba County ................................................................................. 44 12. Packera layneae stalks bending toward the ground, further reducing seed dispersal range.................................................................... 49 vii ABSTRACT THE ECOLOGY AND DISTRIBUTION PATTERNS OF A RARE SERPENTINE ENDEMIC, PACKERA LAYNEAE by Melanie Suzanne Williams Master of Science in Botany California State University, Chico Summer 2014 Many rare and threatened California plant species are endemic to ultramafic serpentine soils. Understanding what specifically makes these species rare is of high value to conservation and management efforts statewide. While there is no one definition of what makes a plant rare, there are many characteristics that are thought to contribute to a species’ rarity. My study focuses on environmental and reproductive attributes of a rare serpentine endemic species to evaluate their contribution to the plant’s rarity. Packera layneae, or Layne’s Butterweed, is a federally threatened and state listed rare species occurring in small, fragmented populations on gabbro and serpentine soils in the northern California Sierra Nevada. I evaluated environmental factors that potentially define its restrictive habitat, including elevation, light availability, duff depth, and slope. I found the studied populations to occur between 2140 and 2920 feet in elevation, and to have established in a variety of habitats where the evaluated environmental factors were moderate, including presence viii beneath intermediate canopy cover (40-60% of available light), widely variable duff depth (0.25 to nearly 6cm), and generally lower slopes (5 to 16%). I also conducted an experiment to evaluate the role of dispersal limitation as a contributing factor to this species’ limited distribution, and found that this species disperses the majority of its seeds very close to the parent plant. I also conducted an experiment to determine the specific germination requirements for P. layneae, and found that its seeds will germinate in a variety of soil types, but only following a period of light exclusion. Using the modeling program Maxent, a species distribution model was constructed using presence locations in conjunction with environmental variables in an attempt to yield a predictive map of potential habitat occupied by this species. Unfortunately, the very small number of known populations available for input into the model, in combination with high environmental variability across presence locations, resulted in a model with reduced predictive function. Determining why this species is so patchily distributed and understanding its unique habitat and physiological requirements will be vital to its conservation