Draba micropetala Hooker

Desjardins, Émilie, Lai, Sandra, Payette, Serge, Dubé, Martin, Sokoloff, Paul C., St-Louis, Annie, Poulin, Marie-Pier, Legros, Jade, Sirois, Luc, Vézina, François, Tam, Andrew & Berteaux, Dominique, 2021, Survey of the vascular plants of Alert (Ellesmere Island, Canada), a polar desert at the northern tip of the Americas, Check List 17 (1), pp. 181-225 : 193

Draba micropetala Hooker

Materials examined. CANADA – Nunavut • Ellesmere Island, CFS Alert ; 82°25′52″N, 062°07′49″W; 296 m a.s.l.; 16 Jul. 2019; habitat: wetland in a mountain pass, with peat and rocks as substrates, dominated by moss and Saxifraga cernua ; QFA0635549 • same locality; 82° 26′34″N, 062°19′06″W; 178 m a.s.l.; 13 Aug. 2019; habi- tat: barren ground on a river bed, with rocks as substrate; QFA0635586 , CAN .

Identification. Plants 2.0– 4.5 cm high; herbaceous; caespitose. Taproots present. Stems 1.0– 3.5 cm long; erect or ascending; hairy, with simple and branched hairs (2–5 rays: T, Y, cruciform, ternate, and dendritic). Leaves basal; alternate or whorled; petiolate or subsessile. Petioles 1–4 mm long; winged; margins ciliate, with simple hairs. Basal leaf blades 5.7–8.0 mm long, 2.1–3.9 mm wide; obovate or oblanceolate; bases attenuate; abaxial surface moderately or densely hairy, with simple and branched hairs (2–4 rays: Y, ternate, cruciform, and dendritic); adaxial surface glabrous or sparsely hairy, with simple and branched hairs (2–3 rays: Y, and ternate); margins ciliate, with simple and branched hairs (2 rays: Y); apices obtuse. Inflorescence a raceme, with 2–4 flowers; elongating or not elongating as the fruit matures. Pedicels 1.0– 4.5 mm long; hairy. Sepals 4; 2.1–2.4 mm long, 0.8–1.0 mm wide; obovate or oblong; green and purpletinged, with yellow margins; surface hairy, with simple and branched hairs (2–3 rays: Y and ternate); margins glabrous; apices obtuse or acute. Petals 4; 2.8–3.7 mm, long; 0.8–1.4 mm wide; oblanceolate; slightly lobed or undulating; pale yellow. Androecium with 6 stamens and 0.3–0.5 mm long anthers. Gynoecium with 1 style and 1 stigma. Fruit a silique; 4.0– 9.9 mm long, 2.7–3.5 mm wide; oblanceolate or obovate; flattened; green; hairy, with simple hairs and branched hairs (2 rays: Y). Styles persisting in fruit 0.05–0.20 mm long, 0.3–0.5 mm wide. Stigma 0.3–0.5 mm wide; as wide as, or slightly larger than, the styles.

Draba micropetala and D. pauciflora both have narrow petals (≤ 2 mm wide) compared to all the other yel- low-flowered Draba species on Ellesmere Island ( D. alpina , D. arctogena , D. oblongata , and D. simmonsii ; Aiken et al. 2007; Al-Shehbaz et al. 2010b; GBIF 2020). In addition, pedicels are usually shorter (1–4 mm long)

in D. micropetala than in D. alpina and D. simmonsii , which have 2.5–30.0 mm long pedicels ( Al-Shehbaz et al. 2010b). D. micropetala and D. pauciflora can usually be distinguished on other characters: D. micropetala has leaves with an obtuse to rounded apex, whereas D. pauciflora has leaves with an acute apex; the leaves of D. micropetala have a predominance of cruciform hairs on the leaves, whereas those of D. pauciflora have a simple and forked hairs; and D. micropetala has ovateelliptic, 2.0– 3.2 mm wide fruits, whereas D. pauciflora has obovate, 3–5 mm wide fruits (Elven and Al-Shehbaz 2008; Saarela et al. 2020). The difference in the fruits did not fit exactly with our specimens from Alert. Instead, we found mainly obovate or oblanceolate, 2.7– 3.5 mm wide fruits in D. micropetala , and lanceolate or elliptic, 1.8–4.0 mm wide fruits in D. pauciflora . However, based on the specimens from Alert, we found that using the dimensions of the styles and stigmas persisting on the fruits were good additional criteria to differ- entiate the two species; D. micropetala had shorter styles (0.05–0.20 mm long) with stigmas as wide as the styles (or very slightly wider), whereas D. pauciflora had longer styles (0.2–0.4 mm long) with stigmas always wider than the styles. As for the other yellow-flowered Draba found at Alert, D. corymbosa , it had even longer styles (0.4–0.7 mm long) and the stigmas were even more distinctly wider than the styles (the two structures appearing like a T).