RARE CONVOLVULACEAE IN THE SOUTHWESTERN UNITED-STATES

Field and herbarium studies of the Convolvulaceae in the southwestern United States indicate that 17 species are rare in all or part of their ranges. Degree of rarity varies. A few show temperate affinities, while most show tropical relationships. Rare Convolvulaceae vary from being exotics introduced in the area to United States endemics. Those species that are globally endangered to threatened are Bonamia ovalifolia, Calystegia longipes, Ipomoea cardiophylla, I. tenuiloba, and I. thurberi. Species that are uncommon throughout their ranges, but not in peril are Bonamia repens and I. lindheimeri. Taxa on the margins of their American ranges are Calystegia macounii, Cressa nudicaulis, Cressa truxillensis, Dichondra argentea, I. dumetorum, I. x leucantha, I. longifolia, I. pubescens, and Jacquemontia agrestis.