Dwarf sandwort (Minuartia pusilla) COSEWIC assessment and status report: chapter 3

Species Information

Name and classification

Scientific name:

Minuartia pusilla (S. Wats.) Mattf.Footnote1

Synonyms:

Arenaria pusillaS. Wats.

Common name:

Dwarf sandwort; annual sandwort; dwarf stitchwort

Family:

Caryophyllaceae; Pink Family

Major plant group:

Angiospermae (flowering plants)

Minuartia is named after Juan Minuart from Barcelona (1693-1768) and Arenaria is from the Latin word arena for sand (Coombes 1985).

Arenaria pusilla was placed in the genus Minuartia based on the capsule opening by as many valves as there are styles. In Arenaria, the capsule dehisces by twice as many valves as styles (McNeill 1980). McNeill and Bassett (1974) place the genus Minuartia in the exstipulate subfamily Alsinoideae following Pax and Hoffmann (1934).

Based on phenetic analysis and seed morphology, Meinke and Zika (1992) have placed Minuartia pusilla in an alliance with M. cismontana (cismontane sandwort) and M. californica (California sandwort). The latter two species are endemic to Oregon and California.

Description

Minuartia pusilla is an annual herb from a weak taproot (Figure 1; Douglas et al. 1998b). The plant has a glaucous tinge (Ceska and Ceska 1980). The stems are erect, solitary or more often, few, simple to branched, glabrous and more or less glaucous, 2-5 cm tall. The basal and lower stem leaves are opposite, linear, 2-4 mm long, less than 0.5 mm wide, glabrous, obtuse, and 1-nerved. The upper stem leaves are few, similar, not much reduced and the stipules are lacking. The inflorescence usually consists of several flowers in an open, leafy-bracted cluster that is often 4/5 the total height of the plant. The petals are elliptic and 1-2 mm long, but sometimes lacking. The sepals are lanceolate, long-pointed or abruptly sharp-pointed, 2-3 mm long, and 3-nerved. The capsules are egg-shaped, 1-2 mm long, and 3-valved. The seeds are brown, about 0.3 mm long, and minutely pimply.

Minuartia pusilla resembles shining starwort (Stellaria nitens), but has entire petals rather than cleft ones found in S.nitens (Ceska and Ceska 1980). It is also similar in appearance to western pearlwort (Sagina decumbens ssp. occidentalis), which has rounded sepals, and slender sandwort (Minuartia tenella), which has glandular-hairy sepals and stems. Minuartia pusilla, in contrast, has pointed sepals and smooth stems. Both species occur in the same type of habitat as M. pusilla.

Figure 1. Illustration of Minuartia pusilla (entire plant on right; line drawing in Hitchcock et al. 1964 and Douglas et al. 1998).Footnote2

 Illustration of Minuartia pusilla

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