Chasing Quercus kelloggii on Santa Cruz Island

Jonathan W. Long, Richard S. Dodd, John J. Knapp, and Angel Fernandez i Marti

Published May 2019 in International Oaks No. 30: 289–294

Abstract

Quercus kelloggii (California black oak) hybridizes with some live oaks to form distinctive trees with persistent leaves. One such hybrid, reported as Q. ×morehus (oracle oak), was collected from Santa Cruz Island in the Channel Islands of California, USA, nearly a century ago. This collection was peculiar because neither Q. kelloggii nor the other parent, Q. wislizeni (interior live oak), are known from the Island. In the summer of 2017, a contractor discovered a tree from which a specimen at Rancho Santa Ana may have been collected, as well as two hybrid saplings. Analysis of nuclear and chloroplast DNA microsatellite results suggested the trees are most similar to Q. agrifolia (coast live oak) and Q. parvula var. parvula (Santa Cruz Island oak), which are both common on the Island. This result suggests that the hybrid might be considered Q. ×chasei, (Chase oak) which is a cross between Q. kelloggii and Q. agrifolia, although it appears to be a three-way combination. We consider whether birds or Native Americans may have brought acorns of either the hybrid or Q. kelloggii to the Island, as has been suspected for a number of other plant and wildlife species, or whether long-distance pollenization might explain the hybrid. Resolving the identity of these isolated trees remains a work in progress, due to the complexity of these introgressed populations and the need for additional sampling. The distinctive chloroplast DNA in the hybrid is a reason to conserve and possibly restore the habitat of this isolated remnant of oak diversity.

Keywords

Quercus agrifolia, Quercus wislizeni, Quercus ×chasei, Quercus parvula var. parvula, oak hybrids, Chase oak, oracle oak, genetics, evolutionary history

References

Anderson, M.K. 2005. Tending the wild: Native American knowledge and the management of California’s natural resources. Berkeley: University of California Press.

Backs, J.R., and M. V. Ashley. 2016. Evolutionary history and gene flow of an endemic island oak: Quercus pacifica. American Journal of Botany 103(12): 2115-2125.

Collins, P.W. 1991. Interaction between island foxes (Urocyon littoralis) and Indians on islands off the coast of southern California: I. Morphologic and archaeological evidence of human assisted dispersal. Journal of Ethnobiology 11(1): 51-81.

Cullings, K.W. 1992. Design and testing of a plant-specific PCR primer for ecological and evolutionary studies. Molecular Ecology 1(4): 233-240.

Darley-Hill, S., and W.C. Johnson. 1981. Acorn dispersal by the blue jay (Cyanocitta cristata). Oecologia 50(2): 231-232.

Dodd, R.S., Z. Afzal-Rafii, and W. Mayer. 2008. Molecular markers show how pollen and seed dispersal affect population genetic structure in coast live oak (Quercus agrifolia Née). In  Proceedings of the Sixth California Oak Symposium: Today's Challenges, Tomorrow's Opportunities, General Technical Report PSW-217, edited by A. Merenlender, D. McCreary, and K.L. Purcell, pp. 485-495. Albany, CA: USDA Forest Service, Pacific Southwest Research Station.

Dodd, R.S., N. Kashani, and Z. Afzal-Rafii. 2002. Population diversity and evidence of introgression among the black oaks of California. In Proceedings of the Fifth Symposium on Oak Woodlands: Oaks in California's Changing Landscape, General Technical Report PSW-184, edited by R.B. Standiford, D. McCreary, K.L. Purcell, pp. 775-785. Albany, CA: USDA Forest Service, Pacific Southwest Research Station.

Erlandson, J.M., T.C. Rick, T.J. Braje, M. Casperson, B. Culleton, B. Fulfrost, T. Garcia, D.A. Guthrie, N. Jew, D.J. Kennett, M.L. Moss, L. Reeder, C. Skinner, J. Watts, and L. Willis. 2011. Paleoindian seafaring, maritime technologies, and coastal foraging on California’s Channel Islands. Science 331(6021): 1181-1185.

Gill, K.M., and J.M. Erlandson. 2014. The island Chumash and exchange in the Santa Barbara Channel region. American Antiquity 79(3): 570-572.

Hauser, D.A., A. Keuter, J.D. McVay, A.L. Hipp, and P.S. Manos. 2017. The evolution and diversification of the red oaks of the California Floristic Province (Quercus section Lobatae, series Agrifoliae). American Journal of Botany 104(10): 1581-1595.

Rogers-Martinez, D. 1992. Northwestern Coastal Forests: The Sinkyone Intertribal Park Project. Ecological Restoration 10(1): 64-69.