The phylogenetic relationships among Calochortus species were investigated using three regions of chloroplast DNA: Two complete spacer regions were sequenced for 72 taxa along with a 500 base that was completed for 35 additional species (Patterson and Givnish 2004). Calochortus tolmiei was found to be sister taxon to C. monophyllus with strong support. Thoungh C. tolmiei is found throughout Oregon and Northern California, it is grouped within the Bay Area clade along with C. uniflorus, C. amabilis, and C. monophyllus, all three of which it can hybridize with (Gerritsen and Parsons 2007).