Ancestral seed zones and genetic mixture of tanoak

Abstract

Understanding the genetic structure of tanoak (Lithocarpus densiflorus) is necessary to pathologists seeking natural variation in resistance to Phytophthora ramorum, cause of sudden oak death (SOD), and to resource managers who need indications of conservation priorities for this species now threatened by this introduced pathogen. We investigated population genetic structure using nuclear and chloroplast DNA in 43 populations from throughout the range of the species. Our chloroplast DNA results revealed four major and two rare haplotypes. The 4 major haplotypes delineated ancestral seed pools from central and northern coastal California, extreme northern California and Oregon, Klamath Mountains and the Sierra Nevada. Diversity at nuclear microsatellite loci supported the chloroplast lineages and indicated some further divergence within them. We propose that at least six breeding zones should be recognized for disease resistance screening and for conservation management. These include 1. southern-most populations from Nacimiento, Lompoc, and Santa Barbara that are relatively low in genetic diversity; 2. central coastal populations from Big Sur to the San Francisco peninsula; 3. populations from north of the San Francisco Bay to Arcata; 4. extreme northern California and Oregon populations from north of Arcata to the northern limit of the species’ range; 5. Klamath Mountains; and 6. the Sierra Nevada.

Parent Publication

• Proceedings of the Sudden Oak Death Fourth Science Symposium

Citation

Dodd, Richard; Rafii, Zara; Mayer, Wasima. 2010. Ancestral seed zones and genetic mixture of tanoak. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M. 2010. Proceedings of the Sudden Oak Death Fourth Science Symposium. Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 171-182