Flora of North America species comparison

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.)

Species 9 (9 in the flora).

Whether Douglasia should be considered a separate genus, part of a very broadly construed Androsace, or, perhaps, part of a new segregate genus comprising Androsace sect. Aretia, has been a longstanding question and remains unresolved. Molecular analyses (G. M. Schneeweiss et al. 2004) show a distinct clade that includes the North American and arctic Douglasia species; it is part of a larger primarily European group of Androsace species in sect. Aretia. Although morphologically very similar to those Androsace species, the Douglasia clade differs in chromosome number (chiefly 2n = 38) and shows a large range disjunction between the Alps and the Bering Strait. As currently construed, Androsace in the broad sense covers a broad range of morphologies, especially in the little-studied Asiatic sect. Pseudoprimula, which, morphologically and karyologically, is closer to Primula than to other Androsace; other sections such as the Chamaejasme group show lesser but still significant discontinuities. Additional comprehensive genetic analyses of the entire Androsace complex are needed before it will be possible to assess the appropriateness of segregate or aggregate nomenclature. This treatment follows the current, conventional view in North America of a segregate generic status for Douglasia.

Throughout its range, Douglasia shows a pattern of closely related species with narrow distributions. The species differ primarily in the type and placement of hairs on the vegetative parts; these characters are consistent and reliable markers. Molecular markers (G. M. Schneeweiss et al. 2004) support close relationships but also indicate separate branches that support species-level designations as well as separate clades within Douglasia, where arctic species form one group and those of the continental northwest, from Washington to Montana, another.

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