-- MADRONO -- Tuesday Nov 22 2005 12:54 PM Allen Press • DTPro System GALLEY 222 madr 52_402 Mp_222 File # 02em MADRON ˜ O, Vol. 52, No. 4, pp. 222–257, 2005 SERPENTINE ENDEMISM IN THE CALIFORNIA FLORA: A DATABASE OF SERPENTINE AFFINITY H. D. SAFFORD 1,2 , J. H. VIERS 3 , AND S. P. HARRISON 2 1 USDA-Forest Service, Pacific Southwest Region, 1323 Club Drive, Vallejo, CA 94592 hughsafford@fs.fed.us 2 Department of Environmental Science and Policy, University of California, Davis, CA 95616 3 Information Center for the Environment, DESP, University of California, Davis, CA 95616 ABSTRACT We present a summary of a database documenting levels of affinity to ultramafic (‘‘serpentine’’) sub- strates for taxa in the California flora, USA. We constructed our database through an extensive literature search, expert opinion, field observations, and intensive use of accession records at key herbaria. We developed a semi-quantitative methodology for determining levels of serpentine affinity (strictly endemic, broadly endemic, strong ‘‘indicator’’, etc.) in the California flora. In this contribution, we provide a list of taxa having high affinity to ultramafic/serpentine substrates in California, and present information on rarity, geographic distribution, taxonomy, and lifeform. Of species endemic to California, 12.5% are restricted to ultramafic substrates. Most of these taxa come from a half-dozen plant families, and from only one or two genera within each family. The North Coast and Klamath Ranges support more serpentine endemics than the rest of the State combined. 15% of all plant taxa listed as threatened or endangered in California show some degree of association with ultramafic substrates. Information in our database should prove valuable to efforts in ecology, floristics, biosystematics, conservation, and land management. Key Words: serpentine, ultramafic, California, endemism, diversity. INTRODUCTION Ultramafic rocks, often called ‘‘serpentine’’ by ecologists, botanists and pedologists, underlie more than 6000 km 2 of the land area of the State of Cal- ifornia (Harrison et al. 2000). The edges of conti- nental plates often include bands of these vestiges of oceanic mantle rock, accreted during the geolog- ic process of subduction, and later uplifted and ex- posed during mountain building and subsequent erosion. Ultramafic rocks and the soils that develop on them are characterized by critically low levels of most principal plant nutrients (N, P, K, Ca), and exceptionally high levels of Mg and Fe and a suite of toxic trace elements including Cr, Ni, and Co. Outcrops of ultramafic rocks support high numbers of edaphic-endemic taxa throughout the world (Brooks 1987). The California serpentine flora is the richest in the temperate zone, and consists of hundreds of species and subspecies that are largely or entirely confined to ultramafic substrates. Serpentine endemism is a key feature of the di- versity of the California flora (Raven and Axelrod 1978; Kruckeberg 2002). Of about 1410 full spe- cies endemic to the State (Hickman 1993), Kruck- eberg (1984) estimated that about 180 were endem- ic to serpentine. If these numbers are at least ap- proximately correct, then about 13% of the plant species endemic to California are serpentine en- demics. This is a remarkably high number when one considers that only 1.5% of the State is under- lain by ultramafic rocks (6000 km 2 /406,280 km 2 ). In addition, because they tend to have small geo- graphic ranges and because many of them occur in the rapidly urbanizing San Francisco Bay Area, ser- pentine endemics are overrepresented among the state’s rare, sensitive, and listed plant taxa (Skinner and Pavlik 1994). The ecology of California’s ser- pentine plants has been extensively studied at the University of California’s Sedgwick Ranch Reserve (e.g., Seabloom et al. 2003; Gram et al. 2004) and McLaughlin Reserve (e.g., Harrison et al. 2003; Safford and Harrison 2004) and Stanford Univer- sity’s Jasper Ridge Reserve (e.g., McNaughton 1968; Huenneke et al. 1990; Hobbs and Mooney 1991). Botanists have relied for two decades on the monograph by Arthur Kruckeberg (1984) for most of their information on Californian serpentine-en- demic plant taxa. Since then, publication of the Jep- son Manual (Hickman 1993), and a proliferation of new botanical research and name changes have left this list in need of updating. Our initial aim was to modify Kruckeberg’s (1984) list, primarily using information from Hickman (1993), to use in our research on diversity patterns (Harrison et al. 2000, 2004). However, it soon became clear that we would have to expand and intensify our search for the best available information. Complicating this effort, plants show a continuum in degrees of ser- pentine restriction, and are sometimes more restrict-