Chloroplast capture creates cryptic lineages with differential geographic patterns in <i>Arctostaphylos uva-ursi</i> (Ericaceae)

Arctostaphylos uva-ursi inhabits circumboreal, alpine, and immediate coastal habitats, while the center of diversity of Arctostaphylos is largely restricted to Mediterranean climates of the California Floristic Province. To discover its relationship to other Arctostaphylos species and to determine whether patterns of variation exist across its circumboreal range, we sampled A. uva-ursi extensively and sequenced ITS and a chloroplast locus, rpl32-trnL. In the cpDNA tree and haplotype network, A. uva-ursi samples appear within two distinct lineages corresponding with different, broad geographic regions, suggesting that one lineage originated via chloroplast capture. Thus, A. uva-ursi contains a phylogenetically typical lineage and a cryptic, chloroplast-captured lineage. Both lineages are widespread, but the lineage with the captured chloroplast is principally on the west coast of North America and dominates our collections from Europe, while the other lineage dominates eastern and northern North America, with some samples in Europe as well. The dominance of the west coast lineage in Europe suggests Beringia as a principal, but not exclusive dispersal path. Reproduction between these two lineages may be responsible for the tetraploid populations found throughout the distribution of the species.