International Carnivorous Plant Society

The Drosera peltata Species Complex

Drosera hookeri

Drosera hookeri. Photo © Richard Nunn.

 

There are a number of ways to typify the art of plant taxonomy. It could be considered a game that has been running for hundreds of years. Field botanists, who are intimately acquainted with live plants, create herbarium specimens consisting of dead, squashed, and dried representatives of plants they find in the wild. They may write descriptions of plants they think are new and give them a name or, as was more common in previous centuries, write a new name next to the specimen and let someone else do the description in Latin. Until recently the specimens were sent off to the great herbariums in Europe where guys sat around in their smoke filled offices, looked for distinguishing characters on the dead plants, compared new specimens to type specimens and decided what is a species and what is not.

During the first 250 years of Linnean taxonomy, there was no globally accessible plant names database, online images of herbarium specimens, or a photofinder. The taxonomists in Europe were it. Now the specimens tend to stay in the country of origin, the field botanists have broad access to type specimens and databases, and they can write descriptions themselves in English. But that does not mean the game is over.

Should the field botanists leave the name game to experts? It could be argued that in fact, the field botanists have nothing to lose naming everything that they think is new. They could hit the jackpot the way Francis Buchanan-Hamilton did when a plant he proposed a name for in 1802 was officially described in Latin in 1824, affirmed in 1848, rejected in 1906, and (finally ?) accepted in 2012.

The taxonomic story of the Drosera peltata complex is long and quite convoluted. The major problem for taxonomists was deciding which characters to use to distinguish the species. As part of his PhD work, Robert Gibson helped solve the problem. The following is a short synopsis based on Gibson, Conn and Bruhl (2012, 2014) of why it took 215 years.

Drosera peltata was first described by Carl Peter Thunberg (1797) based on a plant collected near what is now Sydney, Australia. Subsequently about 12 names were applied to plants in the Drosera peltata complex, most of them not valid for technical reasons (see Schlauer, CP Names Database, for a list of synonyms).

Ludwig Diels (1906, Read online, pp. 110-113) decided, based on the herbarium specimens, the plants attributed to Drosera lunata, Drosera foliosa and Drosera gracilis were really Drosera peltata, leaving that species and Drosera auriculata as the only species he considered to be in the complex. Barry Conn (1981) went even farther and lamented that there was too much variation among the herbarium specimens and it was too hard to tell what was what so he proposed Drosera auriculata be relegated to a subspecies of Drosera peltata.

In the process of doing his review of Drosera peltata, Conn (1981) realized there was no appropriate type specimen for the species. After much sleuthing, he identified a plant (photo at right) that, if it is not the exact plant described, it is from the right location, collected at the right time, and most fits the written description. This plant turned out to be very similar to a plant from Arthurs Lake, Hampshire Hills, Tasmania, that was given the name Drosera gracilis by Joseph Dalton Hooker and described by Jules Émile Planchon (1848, Read online, type specimen at Kew K000215056). In this way the plants that we had recently been thinking of as Drosera peltata var. gracilis were shown to be the Drosera peltata described by Thunberg.

Here the story gets complicated. Gibson, Conn and Bruhl (2012) determined that the Drosera peltata complex consists of at least 5 species based on statistical cluster analysis of characters. The plant originally named Drosera gracilis along with Drosera peltata 'Red Rosette' needed to be separated from the rest of "Drosera peltata" as The Drosera peltata. Thus Drosera peltata became a narrowly described species with densely pubescent sepals and obovoid seeds.

Everything else attributed to Drosera peltata needed to go back to an old name or needed a new name. It was no surprise Drosera auriculata should go back to species status. They also found Drosera lunata should return to species status. A plant named Drosera peltata ‘Western Australian Form’ was different enough it needed a new name. That left one more taxon needing a name. A possible name was Drosera foliosa but that name was applied to Drosera intermedia in 1821, prior to its use for Drosera peltata in 1848.

Gibson, Conn and Conran (2010) coined Drosera hookeri as a replacement name for Drosera foliosa in honor of "Joseph Dalton Hooker (1817–1911) who originally recognized this taxon and provided a manuscript name which was used by J. É. Planchon (1848)". They selected Kew K000215054 (middle plant, top row) from Tasmania as the type specimen as it most closely matched the original concept of Drosera foliosa and most likely was part of the original type collection. Drosera hookeri usually has hairy sepals but some populations have glabrous sepals. The seeds are cylindrical compared to the more pointed seeds of Drosera peltata.

Drosera auriculata was originally described by Planchon (1848, Read online) based on specimens collected by Franz Sieber (Kew K000215087). Planchon used the name suggested by James Backhouse for plants he collected in 1836 near Sydney, Australia (Kew K000215045). Gibson, Conn and Bruhl (2012) selected the plant in the lower right of Kew K000215087 as the type specimen. This plant is generally known by its glabrous sepals and long, thin seeds.

The name Drosera lunata was proposed by Francis Buchanan-Hamilton for a plant that was nominally described by Augustin Pyramus de Candolle (1824, Read online) and more fully described by Planchon (1848, Read online). The type specimen from Nepal selected by Gibson, Conn and Bruhl (2012), BM000752951, is not online but there is a photo in their paper. This species has small ovoid seeds and usually has glabrous sepals.

The name Drosera yilgarnensis was coined for Drosera peltata ‘Western Australian Form’ by Gibson and Conn in Gibson, Conn and Bruhl (2012) with a type specimen chosen from a collection by Phill Mann in 2003 (see photo at right). The name comes from the granite outcrop called Yilgarn Craton where the plants grow. This species has glandular hairy sepals, the style divides into 30 and 60 segments and seeds are small and the most round of the complex.

Lowrie (2013) lists Drosera gracilis as a sixth species of the Drosera peltata complex. Basically, Lowrie contended the type specimen of Drosera peltata on the Sydney, Australia, Thunberg Herbarium 7720 sheet is not the same as the Drosera gracilis type specimen on the Arthurs Lake, Hampshire Hills, Tasmania, Gunn 784 sheet (K000215056). The specimens are close. But whether or not there are differences that can be readily seen on the type specimens themselves—even Lowrie (2013, pg. 480) admits it is difficult sorting collections of even recently dried specimens—the drawing pinned to the herbarium sheet helps make the differences clear (see photo to right). Differences between Drosera peltata and Drosera gracilis are Drosera gracilis plants are less robust with smaller flowers (not valid taxonomic metrics), the upright growth is generally red instead of olive green (questionable taxonomic metric, both have red rosettes), and Drosera gracilis seeds have a hooked tip while Drosera peltata seeds do not (this is a valid taxonomic metric of key value to this species complex (Gibson, Conn and Bruhl (2012))).

Should the name be Drosera gracilis or Drosera peltata subsp. gracilis? Lowrie (2013) states that both Drosera gracilis and Drosera peltata can be found at sites growing together but the plants remain distinct. One South Australia site even has all four species found in that state growing together. So in effect, Lowrie (2013) reversed combining Drosera gracilis with Drosera peltata 'Red Rosette' making 6 species in the complex. This is the back-and-forth of taxonomy in action. Drosera gracilis has glandular hairy sepals and the seeds have a beak-like hook at the tip (see drawing at right).

The taxonomic study of the Drosera peltata species complex is by no means complete. There are a lot of interesting plants out there screaming to be studied.

— John Brittnacher
October 2014

For more information please see:

Candolle, A.-P. de (1824) Droseraceae. In: A.-P. de Candolle (ed.) Prodromus systematis naturalis regni vegetabilis. Treuttel and Wurtz, Paris. (Read online)

Conn, B. J. (1981) The Drosera peltata-D. auriculata complex. Journal of the Adelaide Botanic Gardens 3:91-100.

Diels, L. (1906) Droseraceae. In: A. Engler (ed.). Das Pflanzenreich: regni vegetabilis conspectus. Engelmann, Leipzig, Germany. pp. 1-137. (Read online)

Gibson, R., B. J. Conn, and J. J. Bruhl. (2012) Morphological evaluation of the Drosera peltata complex (Droseraceae). Australian Systematic Botany, 2012(25) 49–80. http://dx.doi.org/10.1071/SB11030

Gibson, R., Conn, B. J., and Conran, J. G. (2010) Drosera hookeri R.P.Gibson, B.J.Conn & Conran, a replacement name for D. foliosa Hook.f. ex Planch. Nom illeg. (Droseraceae). Journal of the Adelaide Botanic Gardens 24:39-42.

Gibson, R. and B. Conn and J. Bruhl (2014) Resolution of the Drosera peltata complex (Droseraceae). Carniv. Pl. Newslett. 43(2):43-48. ( PDF )

Lowrie, A. (2013) Carnivorous Plants of Australia Magnum Opus. 3 Volumes. Redfern Natural History Productions, Poole, GB.

Planchon, J.-É. (1848) Sur la famille des Droséracées. Revisio systematica Droseracearum. Annales des Sciences Naturelles, Botanique séries 3, 9:185–207,285-309. (Read online)

Thunberg, C. P. (1797) Dissertatio botanico de Drosera. In CP Thunberg (ed) Dissertatio Botanica. Edam, Uppsala.

 

Droser peltata

The specimen on the right is the type of Drosera peltata. The specimen on the left is Drosera auriculata and was cut from a different sheet. Thunberg Herbarium 7720 at the Museum of Evolution Herbarium, Uppsala University, Sweden (UPS). Photo © Robert Gibson.

Drosera peltata

Close-up of the Drosera peltata type. Photo © Robert Gibson.

Drosera yilgarnensis

Some of the specimens on the Drosera yilgarnensis type sheet. Phill Mann sheet 18/2003, Mt Madden, Roe region, Western Australia. Photo © Robert Gibson.

Droesra gracilis

Detail of the Drosera gracilis Gunn 784 sheet type sheet (K000215056) from Arthurs Lake, Hampshire Hills, Tasmania. Note the drawings of the seeds. Image © Board of Trustees of the Royal Botanic Gardens, Kew.

 

 
 
 

 Distinctive characters of the species of the Drosera peltata complex.

 

Species*
First Description
Distribution Habitat Plant color      Tuber                  

D. auriculata
Planchon (1848)

Southeastern Australia, in Queensland, New South Wales (including Australian Capital Territory), Victoria, South Australia, Tasmania, and the North Island, New Zealand.

Seasonally moist, rarely wet mineral soils, from sea level to elevations of at least 1300 m.

Olive-green, rarely maroon (Tasmania).

Ovoid to globose, up to 10mm diameter by 8 mm tall; surface white to red.

D. peltata
Thunberg (1797)

Southeastern Australia, in New South Wales (including Australian Capital Territory), Victoria, South Australia and Tasmania.

Coastal and tableland wetlands, always in wet, often peaty soils, sea level to at least 1600 m elevation.

Olive-green to greenish-bronze.

Ovoid, up to 6 mm diameter by 5 mm tall; surface pink to red.

D. gracilis
Planchon (1848)
Southeastern Australia, in New South Wales (including Australian Capital Territory), Victoria, South Australia and Tasmania. From sea level to alpine elevations in wet, sandy or peaty soils. Reddish. Globose, 4 mm diameter; red.
D. hookeri
Gibson, Conn and
Conran (2010)

Southeastern Australia, in Queensland, New South Wales (including Australian Capital Territory), Victoria, South Australia, Tasmania, and far-northern parts of North Island, New Zealand.

A variable species found in coastal, tableland and inland seasonally moist habitats.

Bright yellow-green; rarely reddish to maroon. Ovoid, up to 5 mm diameter by 5 mm tall; surface white to red.
D. yilgarnensis
Gibson and Conn
in Gibson, Conn
and Bruhl (2012)

Roe and Coolgardie regions of Western Australia, with most sites between Hyden, Coolgardie and Salmon Gums.

Granite outcrops in the eastern Wheatbelt and the southern Goldfields, in thin gravelly soil that usually supports Borya sp. herbfields on lower slopes or on aprons of granite outcrops; usually where water accumulates.

Red.

Globose, up to 8 mm diameter, red.

D. lunata
de Candolle (1824)
Western margin of the Pacific Ocean Australia to Japan and east to India. Between Sydney, Australia, and central Honshu, Japan, and east to Shimla, Himcha Pradesh, in the Indian Himalayas. Diels indicated that this species occurs at least as far west as eastern Tajikistan.

From sea level in subtropical locations, to elevations of at least 3600 m altitude in tropical mountains with one herbarium specimen possibly collected from around 6000 m altitude at Jagersar, Uttarakhand, in the Indian Himalayas.

Usually olive-green.

Ovoid, up to 9 mm diameter by 5 mm tall; surface white to red.

 

Species* Flowering           Petals     Sepals Styles Seeds
D. auriculata July–February
(Australia), September–
November (New Zealand)
white or pink

Ovate, elliptic and rarely obovate, 2–6 mm long by 0.9–2.6 mm wide, glabrous with an entire to irregularly serrulate margin.

3, 0.6–1.4 mm long, divided into a total of ~15–30 cylindrical segments.

0.8–1.6 mm long, cylindrical with a shallowly reticulated surface
Drosera auriculata

D. peltata

April–February

white or pink

Ovate–elliptic, 1.5–6 mm long by 1.0–1.5 mm wide, densely pubescent (~5–30 hairs per mm2) with fimbriate margin of glandular hairs up to 0.4mm long .

3, 0.25–1.0 mm long, divided into a total of between ~15 and 25 segments.

0.4–0.8 mm long, ovoid to obovoid by up to 0.3 mm diameter, with a shallowly reticulated surface.
Drosera peltata

D. gracilis August-January white Ovate, 2.5-3 mm long by 1.2-1.5 mm wide with stalked glandular hairs, margin fimbriate with glandular tips. 3, 0.8-1.0 mm long divided in many segments. 0.4-0.45 mm long, ovoid 0.2-0.25 mm diameter, beak-like tapering projection 0.1 mm long, offset to side.
D. hookeri July-December white or pink

Ovate, elliptic or obovate, 2–5 mm long by 0.7–2.4 mm wide, usually moderately to densely hairy (with up to 30 hairs per mm2), but can also be glabrous; always with a fimbriate margin with hairs up to 1.3 mm long.

3, 0.3–1.2 mm long, divided into a total of between ~20 and 30 segments.

0.5–0.8 mm long by up to 0.3 mm diameter, cylindrical, pandurate to obovoid with a deeply pitted surface.
Drosera hookeri

D. yilgarnensis July–November white

Narrowly ovate to elliptic, typically 2–4 mm long by 0.6–1.2 mm wide, margin and apex fimbriate with glandular hairs up to 0.3mm long, adaxial surface moderately hairy (20–40 hairs per mm2) with stalked glandular hairs.

Multiply divided from base into many (usually 30–60) terete segments, up to 1 mm long, white with an orange base.

~0.3–0.5 mm long by up to 0.3 mm diameter, base rounded and apex often apiculate, surface with ~12 longitudinal rows of ovoid pits.
Drosera yilgarnensis

D. lunata

Throughout year. March-
September in
in Australia.

white or rarely pink

Ovate, elliptic, rhombic or ovate, 1.4–4.2 mm long by 0.6–1.8 mm wide, glabrous with the margin entire to serrulate, or denticulate, to partially to fully fimbriate with hairs up to 0.6 mm long. 3, 0.4–1mm long, divided into a total of ~15–30 cylindrical segments.

0.3–0.6mm long by 0.3 mm maximum diameter, ovoid with a shallowly reticulated surface.
Drosera lunata

*Data from Robert Gibson, Barry J. Conn, and Jeremy J. Bruhl. (2012) and Lowrie (2013).
Seed images courtesy of Robert Gibson.

 

Drosera peltata complex seeds on 1 mm grid.

 

Drosera auriculata
Drosera auriculata, Bathurst, New South Wales, Australia.

 

Drosera auriculata
Drosera auriculata, Mt. William, Victoria, Australia.

 

 

 
 
 

Drosera auriculata
Drosera auriculata, Clare Valley, South Australia.

 

Drosrea auriculata
Drosera auriculata, Howden, Tasmania.

 

 
 
 
Drosera auriculata
Drosera auriculata, Cooks Beach, Coromandel, New Zealand.

 

 

Drosera peltata
Drosera peltata.

 

 
 
 

Drosera hookeri
Drosera hookeri, Greenvale, Victoria, Australia.

 

Drosera hookeri
Drosera hookeri, Conara, Tasmania.

 

 
 
 

Drosera hookeri
Drosera hookeri, Brighton, Tasmania.

 

Drosera hookeri
Drosera hookeri, Northlands, New Zealand.

 

 
 
 

Drosera yilgarnensis
Drosera yilgarnensis, Western Australia.

 

Drosera lunata
Drosera lunata, Doi Suthep, Thailand

 

 
 
 

 

Photos of plants in the Drosera peltata complex.
Plants in natural habitat.

 

Drosera auriculata
Drosera auriculata. Photo © Greg Bourke.

 

Drosera auriculata
Drosera auriculata. Photo © Richard Nunn.

 

 
 
 

Drosera hookeri
Drosera hookeri. Photo © Richard Nunn.

 

Drosera peltata
Drosera peltata 'Red Rosette', Victoria, Australia. Photo © Richard Nunn.

 

 
 
 

Drosera gracilis
Drosera gracilis, Tasmania. Photo © Richard Nunn.

 

Drosera lunata
Drosera lunata. Photo © Greg Bourke.

 

 
 
 

Drosera lunata
Drosera lunata. Photo © Greg Bourke.

 

Drosera lunata
Drosera lunata. Photo © Greg Bourke.

 

 
 
 

Drosera yilgarnensis
Drosera yilgarnensis. Photo © Richard Nunn.

 

 
 
 

Drosera auriculata
Drosera auriculata. Photo © Richard Nunn.

 

Drosera peltata
Drosera peltata. Photo © Richard Nunn.

 

 
 
 

 

Close-up photos of flowers.

 

Drosera auriculata
Drosera auriculata, Victoria, Australia. Notice glabrous sepals. Photo © Richard Nunn.

 

Drosera peltata
Drosera peltata, South Australia, Victoria border. Photo © Richard Nunn.

 

 
 
 

Drosera lunata
Drosera lunata, Queensland, Australia. Photo © Greg Bourke.

 

 
 
 

Drosera yilgarnensis
Drosera yilgarnensis. Photo © Robert Gibson.

 

Drosera yilgarnensis
Drosera yilgarnensis. Photo © Richard Nunn.