Drosera mannii — Vorstman's Guide to the Carnivorous Plants

Drosera mannii — the flower — **The flower** · Photo: Denis Barthel — CC BY-SA 3.0 · Wikimedia Commons

Drosera mannii — the habitat — **The habitat** · Photo: Denis Barthel — CC BY-SA 3.0 · Wikimedia Commons

Identification

A small perennial reaching up to 10 cm tall, with the rosette and the tuft of stipules at its heart that mark all pygmy sundews. The flowers are pink. FloraBase gives a flowering time of June to September, earlier than many other pygmy sundews, which flower only in late spring. We did not find precise measurements of rosette, leaf and flower in any source consulted.

Similar species

There are several pink-flowered pygmy sundews in the south-west, including Drosera helodes of the wet coastal plain and D. lasiantha of the southern granite ranges with its woolly-hairy scape. The habitat in jarrah forest on loam and the relatively early flowering are clues, but a secure identification needs details of styles, stigmas and hairs and the key in Lowrie (2013).

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 catch consists of springtails, mites and the smallest flies of the forest floor.

Habitat and ecology

Loam soils in the open jarrah forest of the northern Darling Range (B1, D3, W7), a forest of Eucalyptus marginata on lateritic soils. The codes for laterite and seasonally wet places are derived from the character of that forest, not from a published habitat description. Like all pygmy sundews the plant grows in the wet winter and rests in summer.

Distribution and elevation

Endemic to south-west Australia. FloraBase lists only the Jarrah Forest bioregion, Northern Jarrah Forest subregion: the northern Darling Range, east and south-east of Perth.

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 square is the only one-degree cell — 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. It shows where the species has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No subspecies or varieties have been described. Like most pygmy sundews the plant forms gemmae in the heart of the rosette, which are dispersed by raindrops.

Where and when to see it

Search in winter and early spring in the open jarrah forest of the Darling Range, on bare patches of loam between the leaf litter. Because the plant is small and the flowers open only in sun, a bright day around midday gives the best chance. Mind the risk of the root rot Phytophthora in jarrah forest: clean your boots before and after the visit and keep to the tracks.

Conservation status

On the global IUCN Red List the species is listed as Least Concern (LC); in Western Australia it is regarded as not threatened. It is not listed in CITES. The jarrah forest is under pressure from bauxite mining, logging, the root rot Phytophthora cinnamomi and declining rainfall. Uncertainty: the sources are thin; we could not consult the original description.

Scientific name

Drosera mannii | Cheek, 1990

Described by M. Cheek in 1990, in Phytologia, volume 68, no. 2, p. 86. The only known population is located near Bannister, south-western Western Australia, on clay and peaty sandy soils in a winter-moist watershed. The suffix -ii indicates a dedication to a person surnamed Mann, but exactly who is being honoured could not be established.

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