In this, the first molecular study to sample within the genus Primula at such a large scale, the rpl16 and trnL introns (cpDNA) have been sequenced from 95 of the ca. 450 species, covering 30 of the 37 sections and 5 of the 6 subgenera. Among the 24 additional accessions are representatives of all genera that are likely to be embedded in the primula clade, as well as outgroups from the Maesaceae, Theophrastaceae, and Myrsinaceae. In the strict consensus of the most parsimonious trees, the primula clade is sister to a clade of several genera once thought to be nested in it, including Omphalogramma, Soldanella, and Hottonia. A trichotomy is formed at the base of the primula clade by subgenus Auganthus (plus P. dryadifolia, an enigmatic member of subgenus Aleuritia), subgenus Auriculastrum, and the remaining subgenera. In this last clade are the following well-supported relationships: (i) a clade containing some of the subgenus Aleuritia is sister to subgenus Sphondylia (and Dionysia, see below), (ii) the clade of i is sister to subgenus Primula, and (iii) the clade formed by i and ii is sister to a clade containing the remainder of subgenus Aleuritia (plus the unplaced section Davidii). Four genera are embedded in the primula clade: (i) the Eurasiatic genus Cortusa in subgenus Auganthus, (ii) the North American genus Dodecatheon in subgenus Auriculastrum, (iii) the west Asian genus Sredinskya in subgenus Primula, and (iv) the Middle Eastern genus Dionysia as the sister of subgenus Sphondylia. Homostyly is resolved as a derived condition in two sections (Sphondylia and Proliferae) currently thought to have inherited the primitive homostylous condition of the primula clade. The evolution of characters that have played a significant taxonomic role, including chromosome base number, leaf vernation, and pollen type, will also be discussed in light of the phylogeny.

Key words: Cortusa, cpDNA phylogeny, Dionysia, Dodecatheon, heterostyly, Primula