Flora of North America species comparison

Primula mistassinica is the most widespread of the North American primroses, and one of the more polymorphic. It can vary in size, leaf morphology, and amount of farina; it is generally consistent in overall habit and floral morphology. Infraspecific taxa previously recognized include var. intercedens, a farinose form common around the Great Lakes, and var. novaeboracensis, a form without a prominent yellow eye in the corolla tube. Isolated individuals showing these characteristics appear throughout the range of the species, and an extensive examination of the complex by H. W. Vogelmann (1956, 1960) led him to conclude that it is best treated as a single, highly variable species; recent molecular analyses (A. Guggisberg et al. 2006) support this assessment. Around the Great Lakes, the presence of farina on the leaves is especially variable, and can range from extensive to nonexistent. Consequently, it seems most appropriate to recognize a single polymorphic taxon with no infraspecific designations, unless molecular analysis suggests otherwise. Although smaller forms of P. mistassinica often have been confused with other species in sect. Aleuritia, it is usually distinguishable by its relatively large heterostylous flowers with lavender corollas.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera 20, species ca. 600 (5 genera, 52 species in the flora).

The largest genera in Primulaceae are Primula (ca. 500 species) and Androsace (ca. 100 species). No genera are endemic to the flora area; Dodecatheon and Douglasia have relatively few representatives elsewhere (northeastern Asia).

The family contains ornamental taxa, especially in Dodecatheon and Primula. Primula can cause dermatitis. Some taxa are pollinated by insects; selfing also occurs. Seeds are dispersed by gravity, water, wind, or ants (Primula; B. Ståhl and A. A. Anderberg 2004).

As typically described (e.g., A. Cronquist 1981; V. H. Heywood 1978), Primulaceae were clearly polyphyletic, closely related to Myrsinaceae and Theophrastaceae. M. Källersjö et al. (2000) and B. Ståhl and A. A. Anderberg (2004) removed the nonrosette terrestrial members from Primulaceae in the broad sense and placed them in the Myrsinaceae, which are further distinguished by leaves and calyx often dotted with yellow or dark streaks, flowers with relatively shorter corolla tubes, seeds immersed in placentae, and wood devoid of rays or with multiseriate rays only. Maesa, consisting entirely of trees found in the Eastern Hemisphere tropics, also has semi-inferior ovaries, pedicels with two bracts, and wood with both uniseriate and multiseriate rays; it, too, was removed from Primulaceae/Myrsinaceae and placed in its own family (Källersjö et al.). The families Primulaceae in the narrow sense, Myrsinaceae, Theophrastaceae (including Samolaceae), and Maesaceae then form a monophyletic clade within Ericales (P. F. Stevens, http://www.mobot.org/MOBOT/research/APweb/), sharing some features, most notably flowers with sympetalous corollas, stamens in a single series and opposite the petals, free-central placentation, bitegmic, tenuinucellate ovules, and plants generally with tannins and saponins.

Additional evidence (L. Martins et al. 2003) indicates that Androsace and Primula may not be monophyletic; more work is needed to resolve these issues. The work of M. Källersjö et al. (2000) showed that Douglasia should remain separate from Androsace, and Dodecatheon should remain separate from Primula, although Dodecatheon clearly is derived from Primula subg. Auriculastrum. Alternative views suggesting more inclusive concepts of Primula and Androsace have been offered by I. Trift et al. (2002), A. R. Mast et al. (2004), and G. M. Schneeweiss et al. (2004). The phylogenetic position of Cyclamen, a scapose taxon currently included in Myrsinaceae, has not been resolved. Our understanding of Primulaceae is still in flux, and future taxonomic realignments at the familial and generic levels are to be expected.

(Discussion copyrighted by Flora of North America; reprinted with permission.)