Phylogenetic Relationships and Taxonomic Status Of the Paleoendemic Fagaceae Of Western North America: Recognition Of A New Genus, Notholithocarpus

Abstract

We investigated the phylogenetic relationships and taxonomic status of the castaneoid component {(Lithocarpus} and Chrysolepis) of the family Fagaceae that is endemic to the California Floristic Province {(CA-FP).} Over 7800 basepairs of nuclear and chloroplast {DNA} were analyzed in 17 taxa representing the breadth of phylogenetic diversity in the family. The genus Lithocarpus, as currently defined, is clearly polyphyletic due to the inclusion of L. densiflorus. Here, we designate this taxon as a new genus, Notholithocarpus, which can be recognized morphologically by its relatively small, subprolate pollen. Notholithocarpus is more closely related to Quercus, Castanea, and Castanopsis; Chrysolepis was resolved as the sister group to Lithocarpus sensu stricto. These results indicate that Notholithocarpus does not possess true ‘flower cupules,’ which define Lithocarpus sensu stricto, but like the oaks, the single flower per cupule is derived through the abortion of lateral flowers within each cupule. Further study is required to confirm this characteristic. A formal taxonomic treatment is presented with new combinations.