Abstract
Two chloroplast lineages of tanoak (
Notholithocarpus densiflorus) meet between Korbel and Hoopa in the North Coast of California. Our earlier work suggests these lineages arose from southern and northern glacial refugia and this region represents their colonizing fronts. Earlier, we detected only one population of mixed lineages, suggesting that seedling establishment is limited locally, by short distance seed dispersal in tanoak. North western California and southern Oregon is recognized as a region of divergent lineages for a number of taxa, but it has not been confirmed whether the divergence is due to previous restriction in northern and southern refugia, or a colonizing front carrying rare alleles into new populations. Distinguishing the origin of this divergence is important, as the refugial scenario is likely to have greater implications for genetic adaptations to local environments and possibly for differences in disease resistance. Plant collections were made from the Hoopa Reservation for future resistance screening (Cobb and others 2008) and additional populations were sampled over the transitional zone. We use gene coalescence simulations to test among competing evolutionary scenarios. We detected minimal mixing of chloroplast haplotypes and a weak signal of nuclear DNA divergence across the break. Simulations confirmed the northern and southern refugial hypothesis.
Parent Publication
Keywords
chloroplast DNA,
microsatellites,
Notholithocarpus densiflorus,
refugia,
seed dispersal,
tanoak
Citation
Sandoval-Castro, Eduardo; Dodd, Richard S. 2015. Detecting the limits of northern and southern lineages of tanoak in northern California. In: Standiford, Richard B.; Purcell, Kathryn L., tech. cords. Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world. Gen. Tech. Rep. PSW-GTR-251. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 387-395.
