Cytogenetics and Hybridization of Portulaca in Hawaii

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Abstract
A biosystematic study of Portulaca in Hawaii determined the following chromosome numbers: P. lutea and P. molokiniensis, 2n = 40; P. oleracea, 2n = 54; P. pilosa, 2n = 16; and P. sclerocarpa, P. villosa, two imperfectly known species (P. "olowalu" and P. "ulupalakua"), a P. grandiflora cultivar, and a second unidentified commercial cultivar, all 2n = 18. One plant from the field with 2n = 94 was morphologically intermediate to P. lutea and P. oleracea and apparently represents the stabilized allopolyploid derivative of these species. Additional observations suggest the occurrence of other episodes of natural hybridization involving these species and also P. lutea and P. molokiniensis. Artificial interspecific pollinations yielded the following hybrid combinations: P. lutea times P. oleracea, P. lutea times P. molokiniensis, P. molokiniensis times P. oleracea, P. sclerocarpa times P. villosa, and P. villosa times P. "olowalu." Pollen stainability of hybrids was consistently high in some instances but was low or variable in others. The results suggest that the species of Portulaca in Hawaii comprise two well defined groups: P. lutea, P. molokiniensis, and P. oleracea (polyploids); and P. pilosa, P. sclerocarpa, P. villosa, P. "olowalu," and P. "ulupalakua" (diploids).