Drosera andersoniana — Vorstman's Guide to the Carnivorous Plants

Drosera andersoniana — the habitat — **The habitat** · Photo: Em Lamond — CC BY 4.0 · Wikimedia Commons

Identification

A perennial tuberous plant that shoots anew each year from an underground tuber. At its base stands a rosette of leaves described as closely resembling that of Drosera peltata; above it rises a straight, fairly sturdy stem 8 to 25 cm tall with scattered trapping leaves. The flowers are pinkish white to red and appear in August and September. Precise measurements of leaf blade or petals were not available in the sources consulted for this guide, so trap size is left empty.

Similar species

The strongest resemblance is to Drosera peltata, which also combines a basal rosette with an erect stem. D. andersoniana is distinguished mainly by its stockier, sturdier build, pinkish to red flowers and its restriction to loamy soils around granite rocks in the interior. Other erect tuberous sundews in the same area, such as Drosera graniticola, have white flowers and lack the conspicuous basal rosette.

The trap and how it works

An active flypaper trap spread over two storeys: the ground rosette catches crawling and low-flying animals, the shield-shaped leaves along the stem catch flying insects. Each leaf bears stalked glands with a sticky droplet. A captured insect is enclosed by the surrounding tentacles and digested by enzymes. For a tuberous plant above ground only a few months a year, that extra nitrogen is a real contribution to the new tuber for the following season.

Habitat and ecology

Loamy soils on and around granite outcrops (R3). The granite domes of the Wheatbelt catch the winter rain and shed it down their flanks, so a strip of ground at their foot stays moist longer than the surroundings. There the plant finds enough water in winter; it survives the dry, hot summer as a tuber underground.

Distribution and elevation

Endemic to Western Australia, in the interior east of the south-western coastal plain: FloraBase lists the Avon Wheatbelt, Coolgardie, Mallee and Yalgoo bioregions. The species thus reaches further inland, into the transition to the semi-arid goldfields, than most tuberous sundews.

Recorded (quarter-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 49 quarter-degree squares in which the species has actually been recorded, from GBIF and only from records accurate to within five kilometres. They show where it has been seen, not where it occurs: an empty square means nothing. For threatened species this layer never goes finer than a whole degree, deliberately.

Forms and variation

No subspecies or varieties have been described. The name has a somewhat tangled origin: William Vincent Fitzgerald used it first, but valid publication came only in 1909 through Alfred Ewart and Jean White, hence the author citation 'W.Fitzg. ex Ewart & Jean White'. The species is placed in subgenus and section Ergaleium, the group of erect and climbing tuberous sundews.

Where and when to see it

Visit the Wheatbelt granite rocks in August and September; many are protected nature reserves with walking trails. Search not on the bare rock itself but in the strip of loam and gravel at its foot, where water from the dome collects. The pink flowers are best seen on sunny afternoons. Do not step on the mossy margins of the rock: those fragile mats are home to many rare plants.

Conservation status

Assessed as Least Concern (LC) on the IUCN Red List and listed as not threatened in Western Australia. Not in CITES. The main pressure on its surroundings is the clearing of the Wheatbelt, which has left many granite rocks as islands of bush in a sea of cropland, together with weed invasion and grazing at the foot of the rocks.

Scientific name

Drosera andersoniana | Fitzgerald ex Ewart & White, 1909

Described by William Vincent Fitzgerald, validly published by Alfred James Ewart & Jean White(-Haney) in 1909, in Proceedings of the Royal Society of Victoria, p. 98. The precise type locality could not be established with certainty. The suffix -iana indicates a dedication to a person named Anderson, but exactly who is being honoured could not be established with certainty.

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