New and Noteworthy Species of Boechera (Brassicaceae) I: Sexual Diploids

On the basis of a critical examination of the type collections of all taxa described in Arabis and Boechera from North America, we propose the following nomenclatural adjustments among the sexual diploid taxa. Seven new species of Boechera (B. evadens, B. rollinsiorum, B. serpenticola, B. shevockii, B. texana, B. ultraalsa, B. villosa) are described and new names are proposed for the taxa originally described as A. pulchra var. munciensis (B. lincolnensis) and A. breweri var. austinae (B. breweri ssp. shastaensis). Ten new combinations (B. arcuata, B. atrorubens, B. fernaldiana ssp. vivariensis, B. formosa, B. howellii, B. nevadensis, B. paupercula, B. pendulocarpa, B. polyanthua, B. spatifolia) are validated. Notes on the delimitation, distribution, and/or typification of B. davidsonii, B. holboellii, B. johnstonii, B. lignifera, B. lyallii, B. microphylla, B. pallidifolia, B. pendulina, B. retrofracta, B. sparsiflora, and B. subpinnatifida are presented, with the last species reported for the first time from Idaho, Nevada, and Utah. Arabis davidsonii var. parva, A. demissa, A. hirshbergiae, and A. thompsonii are reduced to synonymy under B. davidsonii, B. oxylobula, B. johnstonii, and B. pallidifolia, respectively.