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Coast Redwood BackgroundCoast redwood (Sequoia sempervirens (D. Don) Endl.) is a hexaploid conifer whose ancestors date to 140 million years before present. Its current natural range is a fairly narrow area along coastal California and southern Oregon, largely coincident with the coastal fogbelt. A highly valued timber species, it is also the foundation species for critical ecosystem services within its range (moderating climate and providing additional moisture through fogdrip condensation) and has much cultural and conservation significance. Along with its distant cousin, giant sequoia or bigtree (Sequoiadendron giganteum), it is honored as California’s state tree. In spite of its many values, molecular genetic studies for this species are relatively recent and sparse, probably because of the difficulty of applying existing protocols to a hexaploid, and one that is quite phylogenetically divergent from other, better studied, conifers. The first allozyme study of the species (Rogers 1997, 1999, 2000) revealed a high degree of genetic diversity in the species—at the higher levels observed for western temperate forest tree species. Because redwood reproduces vegetatively—often in response to fire or other disturbance—as well as sexually, the degree of clonal structure has been an enduring question. A study of clonal structure in old-growth stands revealed modest clonal replication —many trees were not clones (i.e., had only one stem) and those with multiple stems per clone or genotype were typically not large (Rogers 2000). A more recent investigation of fine-scale spatial genetic structure in redwood stands, using spatial autocorrelation analysis and canonical correlation analysis, has shown some differences between upland, fire-influenced forests and lowland, flood-influenced forests (Rogers and Westfall 2004; Westfall and Rogers, in preparation). The high level of putatively neutral genetic diversity revealed by allozyme studies, the fine-scale genetic structuring observed in the presence of potentially long-distance pollen and seed dispersal, and the substantial environmental variation (e.g., elevation, aspect, latitude, soil moisture) within its natural range, all suggest considerable opportunity for local adaptation in coast redwood. A current research proposal (Rogers and Neale, 2006) aims to investigate this potential in a range-wide study of candidate genes for drought response. Results from this investigation will be highly valuable for choosing appropriate reforestation materials and new sites for redwood production areas, contributing significantly to the sustainability of this resource. This information on variability in drought response will also help to inform restoration decisions in National Parks and other areas designated for redwood conservation purposes. GRCP Redwood Research ResultsRogers, D.L. and R.D. Westfall. 2004. Spatial genetic patterns in four old-growth populations of coast redwood. Program for the Redwood Science Symposium, University of California, Berkeley. Rohnert Park, CA March 14–17, 2004. Rogers, D.L. 2000. Genotypic diversity and clone size in populations of coast redwood (Sequoia sempervirens (D.Don) Endl.). Can. J. Bot. 78: 1408–1419. Rogers, D.L. 1999. Allozyme polymorphisms discriminate among coast redwood (Sequoia sempervirens) siblings. Journal of Heredity 90: 429–433. Rogers, D.L. 1997. Inheritance of allozymes from seed tissues of the hexaploid gymnosperm, Sequoia sempervirens (D.Don) Endl. (Coast redwood). Heredity 78(2):166–175. Rogers, D.L. and F.T. Ledig, eds. 1996. The status of temperate North American forest genetic resources. Report No. 16. University of California Genetic Resources Conservation Program, Davis, CA. 102 p. ISBN: 0-9725195-3-X An Annotated bibliography of the
biology of the coast redwood
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