VERTICAL AND LATITUDINAL DISTRIBUTION OF LOTTIA SCABRA AND LOTTIA CONUS ____________________________________ A Thesis Presented to the Faculty of California State University, Fullerton ____________________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Biology ____________________________________ By Kimberly Marie Coombs Thesis Committee Approval: Douglas J. Eernisse, Department of Biological Science, Chair Danielle C. Zacherl, Department of Biological Science Ryan P. Walter, Department of Biological Science Fall, 2017 ABSTRACT Cryptic species can often cause problems for baseline and ecological studies as these species are not readily identified in the field. Lottia scabra and Lottia conus form a north/south cryptic species pair where they occupy the same habitat, but L. scabra is more abundant in northern California and L. conus is more abundant in at least the southern portions of southern California. Past El Nino events have resulted in prolonged anomalous warming of coastal seawater, which may be impacting the vertical and latitudinal distribution of these two species as has been documented for another north/south pair in California, L. austrodigitalis and L. digitalis. To monitor the current and potentially changing distribution of L. conus and L. scabra, quadrat sampling was performed at nine sites in California at various heights in the mid to high intertidal, collecting a subset of limpets to identify in the lab. A range refinement of L. conus has occurred with its previous documented northern limit being Point Conception to now its current northern limit being Jalama Beach, CA. A transition zone occurs from San Pedro to Jalama Beach where L. conus becomes less abundant and L. scabra becomes more abundant. With an established baseline, future studies may document whether this distribution changes in response to temperature variations from climate change or El Nino events. Susceptibility to temperature changes may make limpets good indicator species for detecting regional climate change effects in the intertidal as well as potential model species for future studies to use when observing rocky intertidal habitats. ii TABLE OF CONTENTS ABSTRACT .................................................................................................................. ii LIST OF TABLES ........................................................................................................ iv LIST OF FIGURES ...................................................................................................... v ACKNOWLEDGEMENTS .......................................................................................... vi Chapter 1. INTRODUCTION ............................................................................................... 1 2. METHODS .......................................................................................................... 10 Collection Sites .................................................................................................... 10 Identification ........................................................................................................ 11 Field Sampling ..................................................................................................... 14 Shell Length ......................................................................................................... 15 Shell Volume ....................................................................................................... 16 3. RESULTS ............................................................................................................ 17 Species Proportion and Distribution .................................................................... 17 Density ................................................................................................................. 18 Shell Length and Volume .................................................................................... 20 4. DISCUSSION ...................................................................................................... 26 APPENDICES .............................................................................................................. 43 A. LENGTH AND VOLUME RELATIONSHIP ............................................... 43 B. STUDIED SPECIMENS ................................................................................. 47 REFERENCES ............................................................................................................. 61 iii LIST OF TABLES Table Page 1. Summary of the Total Limpet Densities (# of Limpets/m2 ± SE) of L. scabra and L. conus by Zone and Site ............................................................. 20 iv LIST OF FIGURES Table Page 1. Genetic species identification PCR gel image ..................................................... 13 2. Map of collection sites with species proportions ................................................. 19 3. Lottia scabra high zone length histogram ........................................................... 22 4. Lottia scabra low zone length histogram............................................................. 23 5. Lottia conus high zone length histogram ............................................................. 24 6. Lottia scabra high zone length histogram ........................................................... 25 7. California sea surface temperature in April ......................................................... 34 8. California sea surface temperature in September ................................................ 34 9. Average California aerial temperatures ............................................................... 35 v ACKNOWLEDGEMENTS I would like to thank Douglas Eernisse for accepting me into his lab and supporting me on this project, Danielle Zacherl and Ryan Walter for their support and being on my committee, Christina Burdi for designing the species-specific primers, and the rest of the Eernisse lab for their continued support. I would also like to thank Douglas and Susan Coombs who not only made it possible for me to attain a graduate degree, but who continue to support me on my path as a researcher. I greatly appreciate the funds from a National Science Foundation grant DEB-1355230 to Douglas Eernisse, California State University Fullerton Department of Biological Science, and the Western Society of Malacologists provided in order to conduct this research. vi 1 CHAPTER 1 INTRODUCTION Cryptic species, which are difficult to distinguish based upon morphological characteristics, often require genetic testing for accurate identification (Knowlton 1993; Rocha-Olivares et al. 2004). Cryptic species pose a significant problem for baseline and ecological studies as well as monitoring species diversity and enforcing species conservation and management practices (Knowlton 1993; Sagarin et al. 1999; Geller 1999; Hewitt and Martin 2001; Rocha-Olivares et al. 2004; Wares and Castaneda 2005; Bickford 2006; Burdi 2015). For instance, habitats heavily impacted by pollutants may result in changes in species populations as a result of differences in species pollution tolerance level. Several cryptic species are known to inhabit polluted environments; therefore, if changes result in reductions of a cryptic species that has yet to be accurately identified as a separate species, such reductions might be incorrectly characterized as genotypic selection by researchers or conservation managers, when in fact it would be a loss in genetic diversity that could have larger detrimental impacts for that environment (Rocha-Olivares et al. 2004). Being unable to accurately identify cryptic species inhibits the ability to study them and their habitats, conserve them, and potentially use them as indicator species for environmental change (Bickford 2006). Environmental change, such as increases in temperature due to climate change, El Nino events, and habitat degradation, can result in shifts in cryptic species distributions, 2 especially those that have similar ranges or occupy the same habitat, potentially making these species excellent indicator species. For example, Chthamalus fissus, a cryptic barnacle species with C. dalli, experienced a northward range expansion along the coast of California in response to increased seawater temperature (Barry et al. 1995; Wares and Castaneda 2005). This expansion may cause these cryptic species to be good indicators of environmental change in the rocky intertidal, especially if the southern species, C. fissus, continues to expand its range northward due to increases in temperature and if there is a correlated reduction in the southward range of C. dalli. Shifts in cryptic species distributions in response to environmental change could further impact any ecological interactions between them, especially if cryptic species compete for similar resources in their environment. For instance, Mytilus galloprovincialis, a cryptic mussel species with M. trossulus, competes with M. trossulus for similar resources in their environment along the coast of California. Due to this competition, M. galloprovincialis outcompeted M. trossulus at many sites where they co-occur resulting in a decline of the population of M. trossulus (Geller 1999). Thus, cryptic species in competition with one another could result in a reduction or even a loss of a species at a particular site or area within a site, leading perhaps to negative cascading effects for that environment (Harger