Draba micropetala Hook. Synonyms: pauciflora var. micropetala

Global Distribution: Circumpolar high arctic.

Alaska Distribution: Arctic Tundra.

Ecoregions Occupied: Beaufort Coastal Plain.

Conservation Status: S1S2 GNR; BLM Sensitive.

Description25, 93, 95, 96

1 cm Fruits elliptic-ovate, slightly flattened, 2 to 3.2 mm wide Stem absent

Entire covered with stalked, 2- to 4-rayed hairs and simple hairs

Leaf apexes obtuse to rounded apexes covered with multi- apexes branched, sub-cruciform hairs

Branched caudex sparsely covered by persistent leaf remains

Illustrated by Dagny Tande-Lid, courtesy of Stanford University Press 107

Draba micropetala

General: Caespitose perennial herb from branched caudex sparsely covered by persistent leaf remains; entire plant pubescent with stalked, 2- to 4-rayed hairs and simple hairs, pubescence sometimes sparse towards the top; stems unbranched, lacking leaves.

Leaves: Basal leaves arranged in rosettes, petiolated, broadly oblanceolate to broadly obovate, 6 to 20 mm long, 4 to 12 mm wide with ciliate, entire margins and rounded or obtuse apexes; stem leaves absent.

Flowers: Flowers arranged in racemes of 2 to 7, bracts absent; sepals oblong, 1.8 to 2.5 mm long; petals pale yellow, narrowly spatulate to oblanceolate, 2 to 3 mm long, 1 to 1.5 mm wide.

Fruits: Fruiting racemes elongated; fruiting pedicels spreading to ascending, straight, 1 to 3 mm long; fruits elliptic-ovate, slightly flattened, 5 to 10 mm tall, 2 to 3.2 mm wide; valves often densely pubescent with simple and spurred hairs.

© Geir Arnesen 2007

Ecology

Elevation: Near sea level to less than 10 m.

Landform: Beach ridges, beach fronts, stream banks, frost scars.

Soil Type: Sand, gravel; occurs on both acidic and basic substrates in Svalbard.96

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Draba micropetala

Moisture regime: Moist to dry.

Slope: Flat to moderately sloped.

Aspect: No particular aspect.

Vegetation type: Graminoid-herbaceous meadows, sedge meadows.

Associated species: Alopecurus borealis, Arctagrostis latifolia, Cochlearia groenlandica, Draba lactea, Draba pauciflora, Dupontia fisheri, Hierochloë pauciflora, Poa arctica, Papaver hultenii, Salix rotundifolia, Saxifraga oppositifolia, Silene uralensis ssp. uralensis, Stellaria humifusa; moss.

Longevity: Perennial, short-lived in comparison to many other Draba species;96 most have only one or a few rosettes (some have more than this).

Phenology: In flower in June (and probably earlier); in fruit by early to mid-July.

Population estimate: There are six known occurrences in Alaska; at least one population is locally common.

Reproductive biology: Nearly obligately self-pollinating,97 reproduces by seed; in Svalbard, flowering and seed set is regular and abundant during most years, and mature seeds are regularly observed.96

Similar Species25, 93, 95, 96

Draba micropetala is easily confused with the closely related Draba pauciflora, especially because both species have pale yellow flowers of similar size.98 The two species can be distinguished by the morphological features listed in the table below.

Leaf Leaf Apex Fruiting Species Fruits Seeds Apexes Hairs Racemes Multi- 2 to 3.2 mm Obtuse to branched, wide, 18 to Draba rounded sub- Elongated elliptic- 28 per micropetala apexes cruciform ovate to fruit hairs oblong Mainly 3.5 to 5 mm 8 to 16 Draba Subacute to simple hairs, Congested wide, per pauciflora acute apexes also 2-rayed obovate fruit hairs

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Draba micropetala

1 cm

ALA 38804

© Geir Arnesen 2007

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