Primula alcalina

Primula alcalina is a fibrous-rooted perennial with a basal rosette of leaves and a leafless flowering stem. Leaves are 1-4 cm long, narrowly elliptic with wavy or toothed margins, and taper gradually to a short, winged stalk. The leaf surfaces may have white flake-like farina when young but become mostly glabrous with age. The whitish-green flower stem reaches 6.5-24 cm in height and terminates in an unbranched umbel bearing 3-10 white tubular flowers 4-7 mm long with deeply cleft lobes that are 3-5 mm in length. The bracts below the inflorescence are lanceolate, covered with white farina and 4-7 mm long. The calyx has 5 pointed lobes, and is white farinose and 4-6.5 mm long. Fruit is a capsule.

Primula alcalina is distinguished by its white corollas, generally (at least when mature) efarinose leaves, and small, distylous flowers (Cholewa and Henderson 1984). Albino flowers can be found in any species of Primula, but Kelso (1987) found that beyond these exceptional specimens, flower color is a very useful taxonomic character at both the sectional and species level.

Corolla color fading with age can cause identification problems. Flower color is deepest in buds and young flowers and gradually fades as the flower matures. This is particularly noticeable in the violet-flowered species of section Aleuritia (e.g. Primula incana), where older flowers on herbarium specimens can look almost white (Kelso 1987).

SUMMARY: Wet, alkaline meadows at the headwaters of spring-fed creeks in the large, intermontane valleys. The plants are found on low, relatively level benches adjacent to creeks and spring heads, often on the insides of meander loops, and also on low benches with hummocky topography, but only on the sides and tops of the hummocks. Elevations range from approximately 1920-2040 m. END SUMMARY. Primula alcalina occurs in wet, alkaline meadows, at the headwaters of spring-fed creeks in the large, intermontane valleys of east-central Idaho. Soils in the meadows are alluvial, alkaline, fine-textured, light-colored, and derived from outwash from the predominantly carbonate rocks of the Beaverhead, Lemhi, and Lost River ranges. Soil pH was determined during a demographic study of P. alcalina and found to average 8.9-9.6 at study sites (Moseley 1995). It occurs in the lowest topographic positions in the meadows, where the subirrigated soil is saturated to the surface throughout the growing season. Plants occur on low, relatively level benches immediately adjacent to creeks and spring heads, often on the inside of meander loops, and also on low benches with hummocky topography, where they are found only on the tops and sides the hummocks. While P. alcalina occurs on creek margins, the habitat is relatively stable hydrologically, as the creeks are entirely spring-fed and generally are subject to only minor seasonal or annual fluctuations in flow. Thus, water flows are relatively constant and there is little channel scouring. Elevations of the six populations range from 6,300 to 6,720 feet.

Communities supporting P. alcalina have not been quantitatively described in the literature. Vegetation on benches and hummocks supporting P. alcalina is dominated by Eleocharis pauciflora, Carex scirpoidea, Carex simulata, Kobresia simpliciuscula, and Juncus balticus. Deschampsia cespitosa and Muhlenbergia richardsonis are other common graminoids. Associated forbs are diverse, but not dominant, and include Dodecatheon pulchellum, Triglochin maritimum, and Thalictrum alpinum. Hummocks are often shared with shrubs, including several Salix species, Betula glandulosa, and Potentilla fruticosa. In several cases, meadows with P. alcalina also contain populations of other plant species rare in Idaho, including Kobresia simpliciuscula, Astragalus diversifolius, A. leptaleus, Lomatogonium rotatum, Phlox kelseyi kelseyi, Salix candida, and S. pseudomonticola.

Communities containing Primula alcalina appear to be in an advanced successional stage, that is, they occupy stable landscape positions, and probably have for a long period of time (Moseley 1989). P. alcalina appears restricted to relatively stable habitats that exist along spring-fed creeks that have a fairly constant water flow, causing minimal fluctuations in the water table. It never occurs in meadows along creeks that are subject to seasonal fluctuations and channel scouring, such as caused by flooding during spring. Geomorphic processes that take place along streams of this type appear to preclude P. alcalina habitat (Moseley 1989; Mansfield and Miyasaki 1993). P. alcalina does not occur, or occurs at low density where there is continuous cover of densely tufted or rhizomatous graminoids. Conversely, higher densities are noted where space competition appears minimal, such as bare soil patches and on the side of hummocks (Moseley 1989). Density and other demographic parameters of P. alcalina were found to vary widely among and within sites studied by Muir and Moseley (1994), but causes for the differences could not be conclusively explained. Mansfield and Miyasaki (1993) found that the relationship between P. alcalina density and water table attributes is not linear. Demographic parameters investigated by Muir and Moseley (1994) found a mean of 34 plants per square meter. Numbers of nonreproductive individuals were usually either larger than or roughly equivalent to numbers that were flowering.

P. alcalina populations appear to tolerate a fairly broad range of livestock grazing regimes. It has coexisted with livestock for many years at some sites, and has persisted in areas excluded from livestock as well (Muir and Moseley 1994).

Primula alcalina does not reproduce vegetatively. It is a diploid, distylous obligate outcrosser (Cholewa and Henderson 1984; Kelso 1991). Its relatively uncommon distylous breeding system known as distyly, refers to a floral polymorphism where two morphs (thrum and pin morphs) differ in relative placement of the style and stamens. P. alcalina is probably insect pollinated. Although specific pollinators are unknown, species of butterflies and bees have been observed visiting flowers (Fritts 1992).

During the spring, P. alcalina flowers were abundant at most sites studied by Muir and Moseley (1994). They found an average of 5.1 flowers per reproductive plant. In September, mean number of plants with mature fruits, and of mature fruits per fruiting plant were much lower than numbers of flowering plants and flowers per flowering plant, however. Relatively few plants had aborted fruits in September, suggesting removal of scapes or fruits (e.g., by livestock or small mammals) was more important than lack of seed set as a cause of the low numbers of plants with mature fruits.

The specific seed dispersal mechanisms are unknown for P. alcalina. In primroses studied by Kelso (1987), she found that as capsules ripen and elongation of the scape slows and eventually ceases, elongation and stiffening of the pedicels begins. In fruit, much elongation and stiffening occurs and the fruiting umbel looks very different from the blooming umbel. She speculated that these changes relate to seed dispersal; seeds are shaken out of the capsules by wind or passing animals, and erect elongated pedicels may increase dispersal distance from the parent plant. The process of pedicel elongation begins as scape elongation ceases, and is very rapid. This general development pattern is similar to what has been observed for P. alcalina, where pedicels elongate and stiffen through the growing season. By August, the pedicels are considerably longer than at anthesis and the capsules become erect from the somewhat nodding flower positions at anthesis.