COMPARATIVE WATER ABSORPTION / RETAINING ABILITY BETWEEN CHAPARRAL ISLAND AND THE MAINLAND TAXA: A COMMON GARDEN EXPERIMENT A Thesis Presented to the Faculty of California State Polytechnic University, Pomona In Partial Fulfillment Of the Requirements for the Degree Master of Science In Biological Sciences By Humera Mirza 2019 SIGNATURE PAGE THESIS: COMPARATIVE WATER ABSORPTION / RETAINING ABILITY BETWEEN CHAPARRAL ISLANDS AND THE MAINLAND TAXA: A COMMON GARDEN EXPERIMENT AUTHOR: Humera Mirza DATE SUBMITTED: Spring 2019 Department of Biological Sciences Dr. Frank Ewers, Ph.D. Thesis Committee Chair Professor of Biological Sciences Dr. Edward Bobich, Ph.D. Professor of Biological Sciences Dr. Kristin Bozak, Ph.D. Professor of Biological Sciences ii ACKNOWLEDGEMENTS First of all, I would like to thank Dr. Frank Ewers for his unwavering support and for being an extremely influential mentor in my research and studies. I would not have successfully accomplished my goal of acquiring a Master’s degree in Biological Sciences without his constant guidance and presence whenever I needed it. He gave me the opportunity as an advisor to pursue my dreams while expressing myself in the scientific community. Words cannot express my gratitude to Dr. Ewers for everything he has done for me. I would also like to thank Dr. Bobich and Dr. Bozak for being my thesis committee members. Their guidance was very helpful throughout my research and during the compilation of my thesis. They were my staunch supporters and proponents during the two years of my studies. Shout out to the staff of Rancho Santa Ana Botanic Garden, especially Dr. Loraine Washburn and Helen Smisko, for their assistance in SEM, identifying plants and providing a detailed record of accession. Lastly, I want to thank the Department of Biological Sciences and Cal Poly Pomona for proving me a platform to perform my research and excel in my endeavor to earn a Master of Science degree. iii ABSTRACT Island and coastal species are typically exposed to more fog but less rain than mainland species. Because adaptations to absorb water from fog or mist may be in conflict with those to minimize water loss, I hypothesized that due to natural selection island species would have more capacity to absorb fog and mist due to foliar uptake compared to the mainland congeners. Is the ability to absorb fog or mist a heritable trait? Are there leaf anatomical features that might play a role in water absorption or retention? These questions were investigated by comparing island species to the mainland species in a common garden, namely, Rancho Santa Ana Botanical Garden, where all physical conditions remained the same. Two plant genera (Ceanothus and Arctostaphylos) were selected for this research. The questions and hypothesis were tested by examining leaf water potential, maximum leaf water absorption, hydrophobicity, leaf mass per area, succulence, and the scanning electron microscopy of leaves of island and mainland species. The results suggested that all species exhibit water permeability through their leaf surfaces and demonstrated the capacity to absorb water directly into the symplast. The island and mainland varieties of Ceanothus megacarpus were very similar in water absorption and hydrophobity, but there was a difference in other traits such as leaf mass per area and succulence which were both higher in variety megacarpus than variety insularis. In Arctostaphylos, one of the island species (A. catalinae) experienced high- water absorption, as expected, but the other island species (A. insularis) did not. Arctostaphylos catalinae might have adapted by increasing foliar absorption while A. insularis has more typical mesophytic traits such as having stomata only on the lower surface of the leaf (hypostomatic), low leaf mass per area, and low succulence, compared iv to mainland species of Arctostaphylos. In conclusion, not all the island species are alike. Future experiments might sample the plants in their place of origination to elucidate plastic responses to the island environment. v TABLE OF CONTENTS SIGNATURE PAGE .......................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................... iii ABSTRACT ....................................................................................................................... iv LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii CHAPTER ONE ................................................................................................................. 1 INTRODUCTION ........................................................................................................... 1 CHAPTER TWO .............................................................................................................. 11 METHODS.................................................................................................................... 11 Study Site and Species ............................................................................................... 11 Leaf Water Potential .................................................................................................. 11 Water Absorption Measurements .............................................................................. 11 Hydrophobicity .......................................................................................................... 13 Scanning Electron Microscopy .................................................................................. 14 Statistical Data Analysis ............................................................................................ 15 CHAPTER THREE .......................................................................................................... 17 RESULTS...................................................................................................................... 17 Water Absorption Measurements .............................................................................. 17 Leaf Water Potential .................................................................................................. 18 Contact Angle Measurements .................................................................................... 19 Stomatal Density........................................................................................................ 19 Leaf Mass per Area .................................................................................................... 20 Succulence ................................................................................................................. 20 Scanning Electron Microscopy .................................................................................. 20 CHAPTER FOUR ............................................................................................................. 37 DISCUSSION ............................................................................................................... 37 CHAPTER FIVE .............................................................................................................. 41 CONCLUSION ............................................................................................................. 41 REFERENCES ................................................................................................................. 42 vi LIST OF TABLES Table 1. Sources of material for the common garden study .............................................. 7 vii LIST OF FIGURES Figure 1. Ceanothus megacarpus collected from Rancho Santa Ana Botanic Garden. (a) Ceanothus megacarpus var.insularis showing inflorescences, (b) Ceanothus megacarpus var. megacarpus showing inflorescences, (c) C. megacarpus var. insularis representing leaves, (d) C. megacarpus var. megacarpus representing leaves. ...................................... 8 Figure 2. Arctostaphylos samples collected from Rancho Santa Ana Botanic Garden showing inflorescences. (a) Arctostaphylos pungens, (b) Arctostaphylos glauca, (c) Arctostaphylos catalinae, (d) Arctostaphylos insularis...................................................... 8 Figure 3. Arctostaphylos samples collected from Rancho Santa Ana Botanic Garden with representative leaves. (a) Arctostaphylos pungens, (b) Arctostaphylos glauca, (c) Arctostaphylos catalinae, (d) Arctostaphylos insularis...................................................... 9 Figure 4. Original collection sites for the six species of the two genera used in this study. ........................................................................................................................................... 10 Figure 5. (a) Theta Lite Tensiometer used to measure contact angle, (b) Angle of contact between water drop and leaf shown on screen.................................................................. 16 Figure 6: (a) Water absorption by leaves for Ceanothus same day measurements. Bars represent the mean % increase in leaf water content ±SE and data were analyzed using t- test (two sample assuming equal variance), (b) Water absorption by leaves for Ceanothus following the bench dry treatment. Bars represent the mean % increase in leaf water content ±SE and data were analyzed using t-test (two sample assuming equal variances).