Geographical parthenogenesis in Pacific Northwest hawthorns (Crataegus; Rosaceae)

Abstract

We have demonstrated geographical parthenogenesis in Crataegus series Douglasianae, an agamic complex comprising exclusively tetraploid Crataegus douglasii sensu lato and the morphologically distinct Crataegus suksdorfii complex that comprises diploids and polyploids. Here we characterize ploidy level and breeding system by detailed flow cytometric measurements of the 2C nuclear DNA content of leaf, embryo, and endosperm tissues from 282 black-fruited hawthorns (Crataegus series Douglasianae) representing 33 localities in the Pacific Northwest, one in the Cypress Hills, and three more in the upper Great Lakes basin. We use existing climate and molecular data to place our flow cytometry results in an environmental and evolutionary context. Crataegus douglasii occupies more widely distributed sites that experience more extreme temperature and moisture regimes than do the sites occupied by diploid C. suksdorfii.