Drosera omissa — Vorstman's Guide to the Carnivorous Plants

Drosera omissa — the trap in close-up — **The trap in close-up** · Photo: Devon Peterson in cultivation — CC BY-SA 4.0 · Wikimedia Commons

Identification

A small, fibrous-rooted, perennial rosette with the tuft of stipules at its heart that marks all pygmy sundews, and gemmae at the end of the growing season. We could not check measurements, flower colour or flowering time in any accessible source; those fields are left empty.

Similar species

The closest relative and the obvious confusion is Drosera nitidula, of which D. omissa was long a subspecies; D. leucostigma and D. allantostigma also belong to this alliance. The differences lie mainly in the shape and colour of the stigmas and can only be seen with a hand lens in flowering plants.

The trap and how it works

An active flypaper trap in miniature. The leaf blades carry stalked glands with a sticky droplet; the long marginal tentacles catch the prey and bend it to the centre of the leaf, where shorter glands take over digestion. The prey consists of springtails, mites and the smallest flies.

Habitat and ecology

We were unable to consult a published habitat description. The codes follow the picture of related pygmy sundews on sandy soils in and around seasonally wet hollows and in open heath (W7, D1, B5), and are provisional. The south-west corner between Busselton and Augusta is cooler and wetter than the interior, with a longer growing season.

Distribution and elevation

Endemic to south-west Australia, in the south-west corner between Busselton and Augusta, the area known as the Margaret River district and the Leeuwin-Naturaliste ridge.

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 14 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 are recognised. Like most pygmy sundews the plant reproduces by gemmae, which are flung away by raindrops.

Where and when to see it

Pygmy sundews flower in the south-west Australian spring and open their flowers only in sunshine. In the south-west corner, which is often overcast, it pays to wait for a sunny day. A hand lens is needed to examine the stigmas, the only character that reliably separates this species from D. nitidula.

Conservation status

On the global IUCN Red List the species is listed as Least Concern (LC). It is not listed in CITES. The south-west corner is much in demand for tourism, viticulture and housing, which puts the remaining bushland under pressure. Uncertainty: apart from name, author, section, status and general area we could verify little in a source; the former status as a subspecies of D. nitidula is based on current classification, not on the original literature.

Scientific name

Drosera omissa | Diels, 1992

Drosera omissa was described in 1906 by the German botanist Ludwig Diels, in Das Pflanzenreich (IV.112, Heft 26), page 73, edited by H.G.A. Engler. Diels was working through material gathered during his 1900–1902 expedition with Ernst Pritzel across south-western Australia. The type material comes from south-western Western Australia, the region where Diels and Pritzel collected intensively at the time. However, the precise locality, collector and collection date of the original type material could not be established with certainty; a sheet linked to this name from 1987 (A. Lowrie) likely relates to later taxonomic revisions of the Drosera nitidula complex rather than to Diels' original type material. The epithet omissa is Latin for "omitted" or "overlooked" (from the verb omittere). It likely refers to the fact that this species had been overlooked, or not distinguished from closely related species, in earlier classifications within the Drosera nitidula complex. It is thus a descriptive name, not a toponym or eponym.

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