Lesquerella is United with Physaria (Brassicaceae) Ihsan A. Al-Shehbaz Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A. [email protected] Steve L. O'Kane, Jr.Department of Biology, University of Northern Iowa, Cedar Falls, Iowa 50614-0421, U.S.A. [email protected] Lesquerella (Brassicaceae) is unitedwith the earlier-published Physaria following anunsuccessful attempt to conserve the more specioseLesquerella. Molecular, morphological, distribution-al, and ecological data strongly support the unionof the two genera. Ninety-one names in Lesquerella,including 75 at the specific rank, are transferred toPhysaria. The new names P nelsonii and P reedi-ana are proposed to avoid the creation of later hom-onyms in Physaria. Key words: Brassicaceae, Lesquerella, NorthAmerica, Paysonia, Physaria. The genus Physaria (Nuttall ex Torrey & A.Gray) A. Gray was initially described in Torrey andGray (1838) as a section of the Old World genusVesicaria Adanson and was later raised to the ge-neric rank by Gray (1848). As presently circum-scribed (Rollins, 1993), Physaria consists of 22species distributed from North Dakota south intoNebraska, Colorado, and New Mexico, and westthrough the Mountain and Pacific states, with therange of one species, P didymocarpa (Hooker) A.Gray, extending into southern Alberta, Canada.With the exception of P alpestris Suksdorf, P geyeri(Hooker) A. Gray, and P oregona S. Watson, mostof the remaining 19 species occur in Colorado.Utah, or Wyoming. Both P didymocarpa and P gey-eri were originally described in Vesicaria, but thisgeneric name is illegitimate because it included thetype of the earlier published Alyssoides Miller. Asmany as 37 taxa of North American Brassicaceae(see Rollins & Shaw, 1973; Rollins, 1993) wereoriginally described in Vesicaria, but the vast ma-jority of those were later transferred to LesquerellaS. Watson (Watson, 1888). Lesquerella was established by Watson (1888) asa North American genus distinguished from the ex-clusively Mediterranean Vesicaria by having eden-tate versus dentate filaments and veined instead ofveinless septa. Watson (1888) and Payson (1922)recognized 33 and 52 species in Lesquerella, re-spectively. Rollins (1993) recognized 83 species ofLesquerella in North America, with the range of one,L. arctica (Wormskjild ex Hornemann) S. Watson,extending into Greenland, northern Canada, Alas-ka, and Arctic Russia (Rollins & Shaw, 1973; Tol-machev, 1975). Five additional North Americanspecies were subsequently described (Rollins,1995; Rollins et al., 1996; Anderson et al., 1997;O'Kane, 1999). Although Boelcke and Romanczuk(1984) recognized a single species from Argentina(and Bolivia), we believe that an additional four orfive new species grow in southern South America.The taxonomy of the South American species ofPhysaria will be published at a later late. In his Cruciferae of Continental North America,Rollins (1993) separated Physaria from Lesquerellaprimarily on the basis of Physaria having stronglydidymous fruits with deep sinuses between thevalves distally (apically), and often proximally (ha-sally) as well, as compared to Lesquerella, whichhas non-didymous fruits with no, or shallow, distalsinuses. Additionally, Physaria was said to havesiliques compressed perpendicular to the replumwhile Lesquerella has fruits compressed parallel tothe replum or not at all, a dichotomy that is violatedin several taxa. Lesquerella and Physaria are indis-tinguishable in basically every other morphologicalaspect, including leaf morphology, trichome type,inflorescence, flower color, fruiting pedicels, and allaspects of seed-coat sculpture and embryo type.This remarkable similarity was expressed by Rol-lins (1939: 393), who stated, "The natural relation-ship between Physaria and Lesquerella is verymarked. These two genera have almost exactly thesame floral pattern, habit of growth, and trichomemorphology. The siliques too are very similar."With the exception of the South American speciesand the auriculate-leaved species of Lesquerella ofthe southeastern United States, Physaria and Les-querella have a coherent geographical distribution. NOVoN 12: 319-329. 2002.