Research Within Conservation Biology at the Santa Barbara Botanic Garden: an Intergrated Approach


Dieter Wilken and Ed Schneider,
Santa Barbara Botanic Garden,
USA.

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Abstract

Research in conservation biology at the Santa Barbara Botanic Garden incorporates traditional elements of scientific inquiry. Floristic studies are an integral part of the Garden's research program, providing specimens and data critical to understanding ecological and geographic distribution and to the assessment of rarity. The Garden has collaborated with government agencies in identifying rare plant localities on public lands and the assessment of conservation needs. Herbarium data are available on the internet through cooperative efforts with the US Forest Service, the University of California Berkeley Library, and the US National Plants Data Center. The Garden conducts ecological studies of rare taxa, incorporating in situ work with experimental studies of ex situ populations. These studies are designed to investigate the general reproductive biology of taxa representing different life histories, including trees, shrubs, herbaceous perennials, and annuals. Taxa under study include rare island endemics, whose populations were decimated by over 150 years of herbivory. Studies of pollination, fruit and seed production, seed dormancy, longevity, and germinability, age structure, and suitable sites for experimental populations are planned or in progress. Field studies also have included establishment of experimental in situ populations, which are being used to test hypotheses on reproductive biology under natural conditions, the relative performance of different genotypes, and the potential for long-term survival under varying natural conditions. Collectively they represent a model for understanding general patterns of recovery and potential problems encountered with conservation efforts on California's Channel Islands.

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Introduction

The Santa Barbara Botanic Garden's Mission is dedicated to the study, display, and conservation of California's native flora, through its programs in education, display collections, and research. The Garden has had a long history (over 70 years) of research and horticultural experience. For example, the herbarium, composed of over 130,000 specimens, is particularly rich in collections from the central coast region of California, including the Channel Islands. The living collections display over 1,000 taxa native to California, including over 200 representatives of rare taxa. Among the 7000 native taxa (species, subspecies, varieties) in California's vascular flora, approximately 2150 (or 30%) are endemic (Hickman 1993). Approximately 1750 taxa statewide (or 25% of the total flora) are imperiled by encroachment and development (Skinner and Pavlik 1994). Furthermore, California now supports a human population exceeding 30,000,000, a number that is greater than that of Canada or Australia, for example. The population is projected to exceed 50 million by 2025 (Jensen et al. 1993). Most of the population resides along California's coast, where unique assemblages of plant communities, including the Mediterranean coastal sage scrub, have been severely decimated (Fiedler 1994).

Four botanic gardens in California (Regional Parks, University of California at Berkeley, Rancho Santa Ana, and Santa Barbara) have programs dedicated to conservation biology and each is an active member of the United States Center for Plant Conservation. Each has developed programs that focus on specific regions, taxa, or particular conservation approaches. The Santa Barbara Botanic Garden has chosen to focus on a specific region, the mainland of the south central coast and the California Channel Islands. The mainland portion comprises a relatively natural physiographic region, including several major mountain ranges (e.g. Santa Lucia Range, the western Transverse Ranges), major drainages (e.g., the Salinas and Cuyama River valleys) and encompassing most of 5 of California's 58 counties. Several areas have high levels of endemism, including the Santa Lucia Mountains and the California Channel Islands. Over 300 endemics inhabit the inner south coast ranges and intervening valleys, including major areas of vernal pools and serpentine outcrops (Stebbins and Major 1965, Skinner and Pavlik 1994). At least 100 endemics occur on one or more of the islands, representing about 15% of the total native island flora (Junak et al. 1995). Among these are at least 15 taxa represented by 5 or less populations. At least 6 taxa in the region (1 mainland, 5 island) are considered extinct (Skinner and Pavlik 1994).

The location of the Garden is conducive to growth and maintenance of plants from the region, permitting experimental studies without significant environmental modification. The Garden's propagation facilities and records provide an important resource and accumulated knowledge for the cultivation of native plants. The Garden has good working relationships, including cooperative agreements, with several important land management agencies including the National Park Service and the Department of Defense. These resources facilitate a viable program in conservation biology.

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Conservation Strategies

Recognizing that different circumstances may require different strategies for conservation, the Garden uses an integrated approach to conservation biology, whose aims are to :

  1. Provide thorough information on the rare taxa of its region, through inventories and organization of data useful to management;
  2. Focus on species of special environmental concern that are particularly imperiled and that are showing significant decline; and
  3. Use available information to determine the best approach for conserving and stabilizing populations.

The Santa Barbara Botanic Garden takes an active role in botanical inventories. For example, a recent inventory of rare plants on San Clemente Island, managed by the United States Navy, resulted in discovery of many new and expanding populations of at least 30 species previously thought to be declining, including such endemics as Malacothamnus clementinus (Munz & Johnston) Kearney and Triteleia clementina Hoov. ("Junak and Wilken 1998").

A similar study conducted on Santa Cruz and Santa Rosa islands (McEachern et al. 1997) also established permanent plots for long-term monitoring, based on population age and size-class structure. These kinds of studies permit re-evaluation of priorities for management of other, more deserving taxa, identify endemic-rich areas for special management, and provide a means for tracking taxa of special environmental concern.

The Garden maintains computerized databases that provide important information on the distribution and biology of rare plants. Two kinds of databases are maintained, one using herbarium specimens, the other using original scientific literature. For example, the Garden's herbarium includes over 5000 specimens of rare California taxa. Specimen-based information (e.g. geographic locality, associated species, substrate, date of flowering and fruiting) is provided to appropriate management agencies (Bittman 1994) and is updated regularly. Some data compiled by the Garden is accessible through a website operated by the University of California's Digital Library Project Bioinformatics Library at Berkeley ("www.calflora.org" ). A literature database permits accessibility not only to specimens in other herbaria, but also permits access to critical information on systematics, reproductive biology, and ecology. Integration of such databases will permit access to data that can be organized in different ways, depending upon the question(s) and user needs. For example, the integrated databases make it possible to retrieve all available information on rare taxa of a specific island or mainland physiographic unit, and also retrieve literature relevant to ecological distribution or reproductive biology of included taxa.

The Garden research program gives special attention to taxa of critical environmental concern, including studies of age structure, reproductive biology, and recruitment, which may aid recovery and ensure stable populations (Falk 1987).

For example, studies of 14 rare endemic taxa considered for listing as either threatened or endangered were conducted over a 3-year period (1995-1997) on Santa Cruz and Santa Rosa islands (McEachern et al. 1997). The study combined traditional field surveys and monitoring of population size with studies of population structure, breeding systems, and reproductive biology. Most of the 14 taxa had been reduced to relatively low numbers, primarily as a result of over-grazing for over 120 years (Hobbs 1980, Van Vuren and Coblentz 1987). For example, only 12 populations of the endemic, self-incompatible Dendromecon harfordii Kellogg ssp. harfordii were found on the two islands. Mean population size was 19 ± 5 (median=12). Nine of the populations, with sizes ranging from 5 to 53 individuals) experienced active visitation by insects and produced fruits and seeds comparable to that obtained by experimental enhanced pollination. The remaining three populations, composed of 1, 1, and 3 plants respectively, did not produce any fruits or seeds, despite insect visitation and manually enhanced self-pollination. It was concluded that severely reduced genetic variance for compatibility alleles was the contributing factor to reduced fitness. Because, two of these populations were the remaining representatives of this taxon on Santa Rosa Island, the use of genets derived from Santa Cruz Island represents the only means to ensure recovery and long-term survival on Santa Rosa Island.

Another species, Helianthemum greenei B.L.Rob., is a subshrub known historically from 3 different islands (Santa Catalina, Santa Cruz, and Santa Rosa), but now survives only on Santa Cruz Island. At least 14 populations were documented in 1996, of which ten occurred in mature chaparral or pine woodland. Mean population size at these sites was 9 ± 3 (median=6). Collectively, plants in the ten populations were in the same size class; seedlings and young plants were not evident. In comparison, population size in four other populations in 1996 was 196 ± 98 (median=7.5). These populations occurred in open sites of a chaparral stand that had been burned in December of 1994 (Junak et al. 1995). Since 1996, the number of seedlings has diminished, and populations have stabilized at the same numbers observed in 1996. Studies of ex situ plants at the Santa Barbara Botanic Garden showed Helianthemum greenei to be self-compatible and strongly selfing. Seed germination was significantly enhanced by heat treatment, typical of many fire-adapted chaparral species in the California flora (Keeley 1995). Observations made during these studies, combined with experimental studies, suggest that sufficient banks of seeds may exist at sites wherever Helianthemum greenei is known to occur and that its management may depend on the careful use of fire as a tool to foster larger breeding populations of reproductive genets.

The greatest challenge has been provided by one of California's rarest taxa, the island barberry, Berberis pinnata ssp. insularis. Historically known from 6 populations on 3 separate California Channel islands, island barberry has been severely reduced through grazing by feral animals and erosion. Only 5-7 plants remain at 4 remote localities on Santa Cruz Island. The in situ survival of this taxon depends on understanding its ecological requirements and reproductive biology. Although sample size is severely limited, field and garden studies suggest that this taxon survives best under cool, moist conditions associated with north-facing slopes in woodland or forest habitat. Studies based on two "captive plants" in the Santa Barbara Botanic Garden have shown that plants are self-compatible and that seed germination requires cold stratification under moist conditions. A recovery effort, using seedlings from ex situ plants derived from wild cuttings is planned as an initial effort in recovery.

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Literature Cited


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