Drosera biflora — Vorstman's Guide to the Carnivorous Plants

Identification

A small, flat rosette of short leaves densely set with tentacles, red in sun. The thin scapes carry few flowers; the species name refers to inflorescences often of only two flowers. Reliable measurements and a confirmed flower colour could not be checked in the available sources; the size fields are left empty.

Similar species

More small sundews grow on the same white sands: Drosera esmeraldae in Venezuelan Amazonia, Drosera sessilifolia with sessile, wedge-shaped leaves, Drosera cayennensis with spatulate leaves and more flowers per scape, and in the floodplains Drosera amazonica, which forms an elongated stem. The small number of flowers per scape is a clue, but not a conclusive character.

The trap and how it works

An active flypaper trap on a small scale. The tentacles catch ants, springtails and small flies moving over or just above the white sand; the rosette lies flat on the ground. On the heavily leached white sands this prey provides an important part of the nitrogen.

Habitat and ecology

Open, sunny and extremely poor lowland white-sand savannas and sand flats, with patches that are boggy or flooded in the rainy season and dry out in the dry season (D1, B6, W7). The plant grows among dwarf grasses, Xyris, Eriocaulaceae and bladderworts.

Distribution and elevation

Northern South America: Venezuela, Colombia, Guyana, Suriname and northern Brazil, mainly in the white-sand areas of the Orinoco and northern Amazon basins. A published altitudinal range has not been adopted.

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 7 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 varieties are recognised. As with many small sundews of the Guiana Shield, the boundary with related names is not clear everywhere, and a modern revision of the group with DNA work is still lacking.

Where and when to see it

In the rainy season search bare, wet white-sand patches in savannas, for instance along sandy tracks in the interior of Suriname or in Venezuelan Amazonia. Because the plant is so small it is most conspicuous with flowers open, on sunny mornings. Bring a hand lens.

Conservation status

Not assessed for the global IUCN Red List and not listed in CITES. The species is widespread across northern South America, so there appears to be no immediate cause for concern at species level. White-sand savannas are locally threatened by sand extraction, gold mining and road building.

Scientific name

Drosera biflora | Willdenow ex Roemer & Schultes, 1820

Manuscript name by Carl Ludwig Willdenow, validly published by Roemer & Schultes in 1820, in "Systema Vegetabilium", 15th edition (bis), volume 6, p. 763. "In arenosis humidis Rio Atabapo (Orinoco)" — wet sandy ground along the Río Atabapo (Orinoco basin); lectotype collected by Humboldt & Bonpland (no. 1100). The species occurs in Venezuela, Colombia and the Brazilian Amazon. From the Latin bi- ("two") and flora/florus ("flower") — "two-flowered"; a transparent name, though the exact explanation is not literally confirmed in a source.

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