Chromosome numbers of Australian species of Ipomoea L. (Convolvulaceae)

Abstract

Somatic chromosome counts are reported for 23 species, including the tuber-bearing shrubs I. costata and I. yardiensis and tuber-bearing herbs I. polpha and I. argillicola. The majority are diploids of the basic number x = 15, but 3 exhibit tetraploidy (2n = 60), namely I. plebeia, I. lonchophylla and I. racemigera. The results are discussed in relation to the cytology of other Ipomoea species found worldwide, endemism of Australian species and the possibility of parallel but limited polyploidy as one product of geographically separate evolution in the genus.