Drosera closterostigma — Vorstman's Guide to the Carnivorous Plants

Drosera closterostigma — the flower — **The flower** · Photo: No machine-readable author provided. Denis Barthel assumed (based on copyright claims). — CC BY-SA 3.0 · Wikimedia Commons

Identification

A perennial, fibrous-rooted pygmy sundew with a rosette no more than 1.8 cm across; with its flowering stem the plant reaches 4 cm. At its heart stands the cone of silvery stipules. The flowers are white to pink and appear in October and November. The diagnostic feature is the shape of the stigmas, which are spindle-shaped rather than club- or cushion-shaped. Precise leaf measurements could not be found in the accessible sources.

Similar species

Several white- or pink-flowered pygmy sundews with similar rosettes grow on the northern sandplains and the coastal plain, including Drosera eneabba, Drosera enodes and Drosera dichrosepala. The distinction lies mainly in stigma shape, stipules and calyx, and can hardly be made without a lens and a flower. The habitat, at the margins of wet depressions, helps narrow the search area.

The trap and how it works

An active flypaper trap. The leaves bear stalked glands with a sticky droplet; small animals of the wet sandy ground, especially springtails and gnats, stick to them. The tentacles then bend towards the prey and digestive enzymes are secreted. In pygmy sundews the long marginal tentacles often react within minutes.

Habitat and ecology

Sandy soils at the margins of wet depressions (FloraBase): the zone around seasonal swamps that is waterlogged in winter and dries out in late spring (W7, D1). That late drying fits the flowering in October and November. In summer the plant rests as a bud of stipules.

Distribution and elevation

Endemic to the south-west of Western Australia. FloraBase lists the Geraldton Sandplains, Jarrah Forest and Swan Coastal Plain bioregions.

Recorded (one-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker cells are 3 one-degree squares — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate: the locality of poached species is obscured at source. At this scale that obscuring disappears into the noise. The cells show where it has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No subspecies or varieties have been described. Like all pygmy sundews, the species forms gemmae at the heart of the rosette in late autumn; they are dispersed by raindrops and grow into genetically identical plants.

Where and when to see it

Search in October and early November at the edges of wet depressions on the sandplains, on the transition from wet to dry sand. Kneel and use a hand lens; only then are the spindle-shaped stigmas visible. Photograph the flower from directly above for later comparison.

Conservation status

Assessed as Least Concern (LC) on the IUCN Red List and listed as not threatened in Western Australia. Not in CITES. Seasonal wetlands in the south-west are under pressure from drainage and falling groundwater, but the species' range is relatively large.

Scientific name

Drosera closterostigma | Marchant & Lowrie, 1992

Described by N.G. Marchant & Lowrie, in Kew Bulletin, volume 47, no. 2, p. 322 (29 June 1992). The precise type locality could not be established. The species occurs in Western Australia. From the Greek klostēr ("spindle") and stigma — "spindle-shaped stigma", referring to the shape of the stigmas, which distinguishes this species from related ones.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.