Isozyme variation and the conservation genetics of Garry oak

Abstract

Garry oak ( Quercus garryana Dougl. ex Hook) has a long north–south distribution along the inland Pacific coast. In British Columbia, it is a keystone species in a unique and endangered “Garry oak meadow” ecosystem. Here, we apply isozyme markers to address issues in the conservation and phylogeography of Garry oak. Among 42 populations and 23 gene loci, gene diversity (expected heterozygosity) averaged 0.17, and number of alleles per locus averaged 1.84. These values are about one-half of those found in other white oak species. Using progeny arrays, we found outcrossing rates in two Vancouver Island populations to average 0.96, with no detectable biparental inbreeding; also inbreeding coefficients of the 42 populations averaged near zero (0.025); thus inbreeding is not a significant concern. Cluster analysis of genetic distances identified two major groups of populations: southern Washington – Oregon and Vancouver Island – Gulf Islands; populations within the island region were particularly homogenous. An isolated mainland British Columbia population near Sumas, British Columbia, perhaps of anthropogenic origin, showed the least genetic variability and greatest genetic distance. Generally, geographically isolated populations were more genetically depauperate, which may place handicaps on their survival, but also more genetically distinct, providing a greater evolutionary legacy to the species.