Sedgwick Reserve

30 Apr, 05 PM - 29 Jun, 05 PM

The proposed research is both new research and also an extension of pre-approved research at UC Sedgwick Reserve. In the past, I have made field collections at Sedgwick to determine genetic variation among native grass species at the reserve and also Vandenberg Air Force Base. I have recently been awarded a grant by the National Park Foundation to compare the genetic and ecological variation of three native grass species on the California Channel Islands with grasses on the mainland. Sedgwick and Vandenberg Air Force Base were proposed as the two focal mainland sites. My original proposal to the National Park Foundation is below. ECOLOGICAL AND GENETIC VARIATION AMONG CHANNEL ISLAND AND MAINLAND NATIVE GRASS POPULATIONS BACKGROUND Scientists have long recognized the role of islands as natural laboratories for ecology and evolution (Darwin 1859). The distribution of populations within and among islands and their mainland counterparts provides a unique opportunity to evaluate ecological and evolutionary processes that cause the adaptation of organisms to their environment. In particular, the isolation of oceanic islands results in two features of insular ecosystems that differ from the mainland: 1) a decreased overall number of species, and 2) an increased number of endemic species (Simberloff 1974). These features are explained by the biased arrival on islands of organisms with the ability to disperse long distances, and by the diversification of successful immigrants into ecological niches that were unavailable on the mainland (Carlquist 1974; Simberloff 1974). Studies of island biodiversity and the adaptive radiation of island organisms have traditionally focused on large groups of taxa such as the Hawaiian silversword alliance (28 species in three genera; Carlquist 1970). Many of these studies include endemic plants in efforts to examine speciation resulting from the adaptive specialization of mainland organisms to island habitats (e.g., Ranker et al. 2000). However, the adaptive evolution of organisms on islands may occur at a much more subtle level ? within a single species common to both island and mainland sites. The adaptive evolution within populations of a single species results in different races called ?ecotypes? and the formation of ecotypes is more likely in common, widespread species than in rare or endemic species (Turresson 1936; Krebs 1994). Considerable evidence suggests that plants are adapted to local environmental conditions (Bradshaw et al. 1984). Examples include metal tolerance of plants that grow on mine tailings and herbicide resistance in weedy plants (Linhart and Grant 1996). Given the geographic isolation of island populations, it is likely these populations have diverged from one another over time (due to barriers to interpopulation gene flow). If differences in the genetic structure and genetic composition of plant populations are the result of adaptation to local environments, then genetic variation among populations may be correlated with the ecological characteristics of their habitats. I propose to examine the ecological and genetic variation of populations of three native grass species on the California Channel Islands. I will compare data collected at the Channel Islands National Park with data collected from representative mainland sites in Santa Barbara County. A unique combination of genetic analyses and ecological field studies will allow me to address several questions concerning ecotypic variation of plants distributed between island and mainland habitats. Namely, do island populations of these species resemble mainland populations, or do they represent unique genetic resources? If populations are genetically differentiated, are populations on the same island more similar than on different islands? Similarly, are island populations more similar to each other than mainland populations? Are populations on different islands more distinct from each other than mainland populations separated by similar distances due to stronger dispersal barriers between islands? Does genetic variation correlate with ecological variables such as climate, soil characteristics and rainfall? PROJECT OBJECTIVES My objectives are to use genetic markers and ecological field methods to determine whether populations within single species of native grasses are adapted to island and mainland sites. Specifically, my objectives are to: 1. Survey and quantify the genetic diversity and genetic composition of island and mainland populations of native grasses. These parameters will be used to characterize the spatial scale at which populations have become genetically differentiated, and to estimate the strength of the barriers to gene flow within and between islands, between mainland populations, and between the California mainland and the Channel Islands. 2. Test whether there is a correlation between ecological variables and genetic differentiation of sampled populations. The ecological variables sampled will include climate, rainfall and soil characteristics. 3. Conduct a common garden study of island and mainland plants to test whether morphological differences among populations of native grasses represent heritable genetic variation or plastic responses to different environments. MATERIALS AND METHODS STUDY SITE AND STUDY SPECIES The Channel Islands National Park includes five islands offshore of Central California (Anacapa, Santa Barbara, Santa Cruz, San Miguel and Santa Rosa Islands). Four of the islands are separated by no more than 9.6 km while the fifth (Santa Barbara Island) is separated from the closest of the other four islands by more than 55 km. The climate of the Channel Islands is Mediterranean and strongly influenced by oceanic currents (Moody 2000). The two mainland sites included in this study are Vandenberg Air Force Base and the University of California Sedgwick Reserve. The Vandenberg field site is an annual pasture/grassland located on the southern portion of the base and approximately 4 km from the coastline. The Sedgwick field site is located in the Santa Ynez Valley and is approximately 45 km northwest of Santa Barbara. Sampling sites in the reserve are located in oak savanna-grassland habitat. Invasive annual grasses heavily impact both mainland sites and average annual temperatures are higher than the islands during the spring and summer months (86 degrees F or greater) and may drop below freezing at Sedgwick during winter months. The three native perennial grasses to be examined in this study are purple needlegrass (Nassella pulchra), California brome (Bromus carinatus), and blue wildrye (Elymus glaucus). These grasses are dominant species in native California grassland ecosystems and are common to Sedgwick Reserve and Vandenberg Air Force Base. N. pulchra and B. carinatus are reported to be present on all five Channel Islands while E. glaucus may have a more limited distribution (Santa Cruz and Santa Rosa Islands; Smith 1976). The three species represent a range of mating systems from highly self-fertilizing (Elymus; Knapp and Rice 1996) to mixed mating (Bromus) and outcrossing (Nassella). Plant mating or breeding systems (defined as the percent of progeny that result from outcrossed fertilization) strongly influence the distribution of genetic diversity in populations and affect both gene flow and levels of local adaptation (Hamrick et al. 1991). As a consequence, the mode of reproduction may determine the geographic scale (within and between island and mainland sites) over which I see local adaptation in these species. During the last year, as part of a complementary study of ecological adaptation in these species in mainland populations, I have gained considerable experience in germinating and cultivating these species in the greenhouse and in the field. GENETIC MARKERS Genetic differentiation between surveyed populations will be detected with ISSRs (inter-simple sequence repeats) and microsatellite markers. ISSRs provide a genetic ?fingerprint? for each individual sampled and are often distinguishable among populations (Wolfe et al. 1998). Microsatellites are segments of repetitive DNA present in plants and animals, and are routinely used to estimate genetic diversity, plant mating systems and rates of gene flow (Tautz and Renz 1984). Genetic fingerprints, or diversity estimates, will determine the extent of variation between surveyed populations. FIELD SAMPLING At both island and mainland sites, I plan to collect leaf tissue for each species from a minimum of 30 plants of 10 populations per site. In addition, I will collect approximately 10 seeds from 30 plants per population for use in the experimental study of plant growth during the second year. Native grasses produce enormous quantities of seeds and our collections should not impact island or mainland populations. In addition, seeds collected from several plants of each population will ensure that our samples do not represent a biased distribution of genetic variation. ECOLOGICAL VARIABLES On the dates of leaf tissue collection at each site, I will extract three soil samples per population (approx. 500 grams per sample) for later analysis at the UC Davis DANR Analytical Laboratory. Soil samples will be analyzed for nitrogen mineralization potential, soil pH, total carbon and nitrogen, and available potassium and calcium. To the extent possible, I will also collect data for the rainfall and temperature at each site (these data will be obtained from meterological stations on the islands and at each mainland site). Data for soil characteristics, rainfall, and climatic (temperature) variables will be combined with estimates of the genetic similarity of populations to test whether the geographic variation of population genetic differentiation is correlated with variation in island and mainland habitats (Wilson et al. 2001). COMMON GARDEN STUDY During Fall 2003, a common garden of seeds of each species from island and mainland sites will be established at the University of California in Santa Barbara. Namely, I will plant seeds from each species and site (island or mainland) in a common environment. Plants will be subsequently monitored for differences in life history and reproductive characters (e.g., growth rate, flowering time, panicle height). Morphological differences observed within species and among sites would suggest heritable genetic variation between populations. Morphological differences among island and mainland sites would be evidence for ecotypic variation and possible local adaptation among populations of a single species. SIGNIFICANCE OF THE RESEARCH Basic ecological research includes the study of the differentiation of populations within species to detect evidence for their adaptation to local environments. The Channel Islands represent a unique environment to test the theory that common, widespread plant species are likely to differentiate into separate races or ecotypes. The proposed study will examine both genetic and ecological variation among populations of three native grass species, and will represent the first study to detect evidence for genetic and ecological differentiation of mainland vs. island populations. In addition, studies of multiple populations will enable us to test predictions of the distribution of genetic variation among island and mainland sites. A combination of field and experimental methods with ecological genetic marker analyses will provide new insights in the local adaptation of native species, and contribute to the island biogeography of plant populations. These data may also assist efforts for the conservation and restoration of unique genetic resources represented by native California perennial grasses. REFERENCES CITED Bradshaw, A.D. 1984. Ecological significance of genetic variation between populations. Pp. 213-228 in R. Dirzo and J. Sarukhan, eds. Perspectives on plant population ecology. Sinauer Associates, Inc. Sunderland, Massachusetts. Carlquist, S. 1970. Hawaii, a natural history. Natural History Press, New York. Carlquist, S. 1974. Island Biology. Columbia University Press, New York. Darwin, C. R. 1859. On the origin of species by means of natural selection. (6th ed., 1971). John Murray, London. Hamrick, J.L., M.J.W. Godt, D.A. Murawski, and M.D. Loveless. 1991. Correlation between species traits and allozyme diversity: implications for conservation biology. Pp. 75-86 in D.A. Falk and K.E. Holsinger, eds. Genetics and conservation of rare plants. Oxford University Press, New York. Knapp, E.E. and K.J. Rice. 1996. Genetic structure and gene flow in Elymus glaucus (blue wildrye): Implications for native grassland restoration. Restoration Ecology 4:1-10. Krebs, C.J. 1994. Ecology: The Experimental Analysis of Distribution and Abundance. Harper Collins, New York. Linhart, Y.B., and M.C. Grant. 1996. Evolutionary significance of local genetic differentiation in plants. Annual Review of Ecology and Systematics 27:237-277. McNaughton, S.J. 1973. Comparative photosynthesis of Quebec and California ecotypes of Typha Latifolia. Ecology 54:1260-1270. Moody, A. 2000. Analysis of plant species diversity with respect to island characteristics on the Channel Islands, California. Journal of Biogeography 27:711-723. Philbrick, R.N. and J.R. Haller. 1977. The southern California islands. Pp. 893-906. In M.G. Barbour and J. Major, eds.) Terrestrial vegetation of California. Wiley, New York. Ranker, T.A, C.E.C. Gemmill, and P.G. Trapp. 2000. Microevolutionary patterns and processes of the native Hawaiian colonizing fern Odontosoria chinensis (Lindsaeaceae). Evolution 54: 828-839. Simberloff, D.S. 1974. Equilibrium theory of island biogeography and ecology. Annual Review of Ecology and Systematics. 5:161-182 Smith, C.F. 1976. A Flora of the Santa Barbara Region, California. Santa Barbara Museum of Natural History, Santa Barbara, CA. Tautz, D. and M. Renz. 1984. Simple sequences are ubiquitous repetitive components of eukaryotic genomes. Nuceic Acids Research 12:4127-4138. Turresson, G. 1925. The plant species in relation to habitat and climate. Hereditas 6:147-236. Turresson, G. 1936. Rassenkologie und Pflanzengeographie. Bot. Not. 420. Wilson, B.L., J. Kitzmiller, W. Rolle, and V.D. Hipkins. 2001. Isozyme variation and its environmental correlates in Elymus glaucus from the California Floristic Province. Canadian Journal of Botany 79:139-153. Wolfe, A.D., Q. Xiang, and S.R. Kephart. 1998. Assessing hybridization in natural populations of Penstemon (Scrophulariaceae) using hypervariable intersimple sequence repeat (ISSR) bands. Molecular Ecology 7:1107-1125.

Visit #1364 @Sedgwick Reserve

Approved

Under Project # 1139 | Research

Ecological and genetic variation among Channel Island and mainland native grass populations

research_scientist - University of California, Santa Barbara

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Kristina Hufford Apr 30 - Jun 29, 2003 (61 days)

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Day Use Only 1 Apr 30 - Jun 29, 2003