Hand.-Mazz.
Description
Androsace rhizomatosa is a high-alpine cushion plant of the eastern Himalaya, known in GBIF from a single Bhutanese record, an emphatic indication of its rarity and very restricted distribution. It is a plant of exposed alpine screes, rocky ridges, gravelly flushes and turf at the upper limits of vegetation. The collection at Jule-Tso in Bhutan at about 4400 m in June is consistent with the cold, windswept, well-drained high-alpine habitat the species occupies, flowering in early summer as the snow retreats from these stony slopes well above the treeline.
The species is a small perennial herb of the genus that, as its epithet rhizomatosa indicates, spreads by slender rhizomes or stolons to form loose mats or low cushions of leaf rosettes rather than tight hemispherical domes. The leaves are small, narrow and crowded into basal rosettes, often grey-green and clothed with fine hairs that reduce desiccation and ultraviolet damage. The flowers are borne singly or in small few-flowered umbels on short scapes; each has a salver-shaped corolla with five spreading lobes, white to pale pink with a contrasting yellow or pinkish eye at the constricted throat, and the stamens inserted within the corolla tube. The fruit is a small few-seeded capsule.
Androsace (Primulaceae) is a large Holarctic genus richly developed in the Himalaya and Tibetan Plateau, where rosette- and cushion-forming species are repeatedly adapted to cold, arid, high-irradiance alpine conditions; A. rhizomatosa belongs to the rhizomatous, mat-forming element rather than the dense-cushion section. Its compact growth conserves heat and moisture, and pollination is by alpine insects. Given that it is documented from essentially a single locality and confined to a fragile high-alpine niche, the species is of considerable conservation concern and merits dedicated field survey and assessment.
Author: Hand.-Mazz. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Smith and Lowe Androsaces, Annotated Checklist of the Flowering Plants of Nepal