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Understanding of the taxonomy of the genus Drosera developed significantly during the 20th and early decades of the 21st century, with more than 100 new species described since 1950 and several revisions to the accepted taxonomy. More recent taxonomic revisions have been informed by phylogenetic analysis as well as morphology, distribution and other factors.

History

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18th century

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The genus Drosera was first circumscribed by Carl Linnaeus in his 1753 Species Plantarum,[1] where he described 5 species. Three of these are still recogised as Drosera species: the type species D. rotundifolia; D. capensis; and D. indica. The description of D. longifolia was ambiguous and the name was formally rejected more than two centuries later[2] due to confusion between D. anglica (named by William Hudson in 1778)[3] and D. intermedia (named by Friedrich Hayne in 1798).[4] D. lusitanica was moved to the monotypic genus Drosophyllum by Johann Heinrich Friedrich Link in 1805.[5]

19th century

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In 1824 Augustin Pyramus de Candolle made the first systematic revision of the genus, covering 32 species including several newly described by de Candolle.[6] This work included an infrageneric classification of Drosera into two subgenera based on the morphology of the style: D. subgen. Rorella (styles simple or divided into two or three parts) and D. subgen. Ergaleium (apex of style divided into many parts), with each subgenus further split into two series.[7]

In 1844, Johann Lehmann published 9 new species of Drosera along with the new genus Sondera, containing two Australian species—S. preissii and S. macrantha—which he described as ‘Droseracearum habitu’ (in the habit of Droseraceae).[8] The new genus was not widely accepted. Its two species are now considered synonyms of D. heterophylla and D. macrantha respectively,[9][10] and Sondera is regarded as a synonym of Drosera.[11]

By the late 1840s, the number of described Drosera species had grown significantly, thanks in particular to the botanical explorations of South America by Augustin Saint-Hilaire and of Western Australia by James Drummond among others.[6] In 1848, Jules Emile Planchon—a former student of Saint-Hilaire—published a new treatment of Drosera in the Annales des sciences naturelles. Botanique. This covered 85 species, which Planchon arranged into 13 sections based on morphological characteristics including style division. The last of these, D. sect. Ergaleium, was further subdivided into three series and two subseries.[12]

George Bentham's 1864 Flora Australiensis provided coverage of the growing number of Australian Drosera. Describing Planchon's study of the genus as "excellent", Bentham nonetheless found that his sectional division "appears to me not to tend towards clearness of method, but rather to confuse the mind". Bentham therefore followed, with slight modifications, De Candolle's earlier arrangement with the two sections Rorella and Ergaleium.[13] The same arrangement was followed in Bentham and Hooker's Genera Plantarum.[14]

In 1886 the Prussian botanist Berthold Stein published a treatise on Droseraceae in Gartenflora, following Planchon's 13 sections but recognising only 81 Drosera species.[15] Two years later, the German botanist Carl Georg Oscar Drude published an alternative treatment of Droseraceae in Engler and Prantl's Die Natürlichen Pflanzenfamilien. Drude recognised five subgenera of Drosera, with the first, subgen. Ros-solis, comprising two sections.[16]

20th century

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In 1906, the first true monograph of Droseraceae was published in Das Pflanzenreich by another German botanist and collector, Ludwig Diels. Diels' work was still considered the standard reference for Drosera anatomy and morphology more than a century later.[6] Diels praised the careful work of Planchon, whose division of Drosera into 13 sections he said "reflects the view that still seems to be the only possible one".[a] He was dismissive of Drude's system, in which "not much has improved over Planchon, but some of the good things about his classification have been abandoned".[b] Drude's grouping of Planchon's sections Lamprolepis and Thelocalyx was described by Diels as "dubious" (bedenklich) and his combination of sections Ptycnostigma, Lasiocephala and Phycopsis "unquestionably contrary to nature" (zweifellos naturwidrig).[17]: 54 

Diels re-introduced a subgeneric division of Drosera, subordinating most of Planchon's 13 sections to the three subgenera Rorella, Ptycnostigma and Ergaleium, which he felt more clearly represented the relationships within the genus. He emphasised the importance of subgen. Ptycnostigma (into which he merged Planchon's sect. Arcturia),[17]: 62  considering this subgenus particularly isolated from other Drosera.[17]: 54  Other modifications which Diels regarded as less significant included the withdrawal of sect. Crypterisma,[17]: 55  which was merged into sect. Rossolis;[17]: 81  the demotion of sect. Lasiocephala to a series within this section; and the restructure of Planchon's series within Ergaleium into sections Polypeltes (containing the former series Scutiliferae and Luniferae plus D. banksii)[17]: 109  and Erythrorrhiza (from Planchon's series Erythrorhizae).[17]: 122 

Infrageneric Taxonomy

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This page reflects the infrageneric taxonomy used by Fleischmann, Cross, Gibson, Gonella & Dixon (2018),[18] with taxa published or revised since that date placed according to the relevant authors.

Drosera subgenus Drosera

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Section Arachnopus

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Originally recognised by Planchon in 1848,[19] sect. Arachnopus is sometimes known as the 'Drosera indica complex'[20] and now comprises at least 13 recognised species. All species in this section are believed to be annual therophytes and the majority are endemic to northern Australia, although two species are also found in Asia and one only in Asia and sub-tropical Africa.[18] The name Arachnopus refers to the 'spider leg' form of the plants (from Greek: arakhne [spider] + pous [foot]).[6]

Section Brasilianae

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Section Brasilianae was published in 2018, based on molecular phylogenetic data which showed that the previous circumscription of Drosera sect. Drosera was not monophyletic. It comprises the 'Brazilian tetraploid' clade of at least 18 species native to South America.[21] The section was originally published as sect. Brasiliae but this name was found to be grammatically non-compliant with the rules of the International Code of Nomenclature and was formally corrected by the authors later the same year.[22]

Section Drosera

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This section contains the type species of Drosera, D. rotundifolia. In the present taxonomy it comprises diploid species primarily from Eurasia and the Americas, although D. spatulata is also found in Australia and New Zealand.[21] The section previously contained many more species, but molecular phylogenetic analysis by Rivadavia et al. in 2003 showed that the section was polyphyletic.[23] Subsequent publications separated section Brasilianae and re-established sect. Ptycnostigma.

Section Prolifera

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This section, which was published by Cyril Tenison White in 1940[24], comprises species endemic to Far North Queensland. They are the only Drosera species that grow solely in rainforest habitat. Each appears to favour a different micro-habitat within their range, which roughly parallels the eastern coast. The section was sometimes referred to as the 'Three Sisters',[25] but the publication of D. buubugujin in 2020[26] added a fourth member. The section name refers to asexual reproduction via 'daughter' plantlets produced from the flower stalks, a characteristic particularly noted in D. prolifera (from Latin proles [offspring] + ferre [to carry / bear]).[27]

Section Psychophila

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This section was first published by Planchon in 1848,[28] containing two species with a sub-Antarctic distribution. The section name is assumed to derive from a misspelling of the Latinised form of the Greek psykros (cold) and Greek philos (love) i.e. cold-loving.[27] Stein used the spelling Psychrophila in his 1886 work[15] and Drude later proposed the name Psychrophilae for a section containing the same species.[16]

Section Ptycnostigma

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Section Ptycnostigma was first published by Planchon in 1848,[29] initially with only four species (two of which, D. helianthemum and D. speciosa, are now considered synonymous with D. cistiflora[30]). Marchant, Ashton and George reduced the section to synonymy with sect. Drosera in 1982,[31] but Seine & Barthlott recognised it as a separate section in 1994.[32] It was significantly expanded based on molecular phylogenetic data in 2018 by Fleischmann et al., such that it now comprises all the African sundew species except D. regia (D. subgen. Regiae) and D. indica (D. sect. Arachnopus), many of which do not share the distinctive multifid-flabellate stigma shape that originally distinguished the section.[21]

Section Stelogyne

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This section was first published by Diels, who noted the unique fused styles of D. hamiltonii in his 1906 monograph.[33] The significance of this feature has been debated by taxonomists. The section was reduced to synonymy with D. sect. Drosera by Seine and Barthlott in 1994 (based on pollen morphology),[32] resurrected and elevated to subgenus by Schlauer in 1996,[34] and returned to section level within subgenus Drosera by Fleischmann et al based on molecular phylogenetic data.[18]

Section Thelocalyx

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Section Thelocalyx comprises two tropical species of compact, rosette-forming sundews.[27] The section name was given by Planchon in 1848[35] and refers to a covering of papillose projections found on the sepals (from Greek thilí [nipple] + kályx [outer covering, sepal]).[27]

Drosera subgenus Ergaleium

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Section Bryastrum

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This section comprises the pygmy sundews, tiny species mostly native to Western Australia, many of which reproduce primarily via production of gemmae. The section was named by Planchon in 1848,[36] the name referring to the starry appearance of the plants and their habit of forming moss-like clumps (from Greek bryos [moss] + astron [stars]).[27]

Section Coelophylla

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This monotypic section was first published by Planchon in 1848.[37] Its sole species is endemic to Australia, where it is widespread. The section name refers to the depression in the centre of the lamina (from Greek: koilomat [hollow] + phyllum [leaf]).[6]

Section Ergaleium

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Section Ergaleium contains the 'tuberous' sundews, geophytic species which undergo summer dormancy in the form of subterranean tubers.[18] The section was first published in A.P. de Candolle's 1824 Prodromus Systematis Naturalis Regni Vegetabilis, initially containing 6 species[38] (only three of which remain today; the others being D. binata which now has its own section Phycopsis; its synonym D. pedata; and D. banksii which is now placed in sect. Lasiocephala). Species now placed in sect. Ergaleium include those that formerly comprised the sections Erythrorhiza and Stolonifera, which were not supported by molecular phylogenetic analysis.[23] The sections Luniferae and Macrantha proposed by Allen Lowrie are also now considered synonymous with sect. Ergaleium.[39]

Section Lasiocephala

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Section Lasiocephala (from Greek lasios [shaggy] + kephale [head], describing the densely hairy growth points of these species) was first published by Planchon in 1848.[40] It currently comprises the species of the 'D. petiolaris complex' plus two erect species. Several further taxa are currently awaiting formal description. Species of this section are found mostly in northern Australia as well as the Torres Strait Islands and southern Papua New Guinea.[41]

Section Phycopsis

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This section was published by Planchon in 1848.[42] Its sole member is native to Australia, New Zealand and the Chatham Islands[43] and is distinguished by its branching leaves, which are compared to seaweed in the section name (from Greek phykos [seaweed] + opsis [appearance]).[27]

Drosera subgenus Arcturia

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Subgenus Arcturia contains two cold-tolerant species endemic to southern Australia, Tasmania and New Zealand.[6] Alongside subgenus Regiae, it is considered ancestral to the two larger clades (subg. Drosera and Ergaleium above) that contain the vast majority of sundew species.[21] Arcturia was originally published at section rank by Planchon in 1848,[44] containing only the type species D. arcturi. It was elevated to subgenus by Schlauer in 1996[34] and this placement was later supported by molecular phylogenetic analysis.[21] The subgenus name refers to Mount Arthur in Tasmania, from which the type specimen of D. arcturi was collected.[45]

Drosera subgenus Regiae

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The unique species D. regia, a large sundew endemic to a very restricted locality around the Bainskloof Pass in South Africa,[46] was placed into its own subgenus in 1994 by Seine & Barthlott.[32] Subsequent DNA analyses have confirmed its apparently ancestral position in the phylogeny of Drosera alongside subgenus Arcturia.[18]

Notes

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  1. ^ "Seine Gliederung von Drosera in 13 Sektionen giebt daher im wesentlichen die Auffassung wieder, welche auch heute noch die einzig mögliche erscheint."
  2. ^ "Auch in dem System von Drude ist gegenüber Planchon nicht viel gebessert, dagegen einiges Gute seiner Klassifikation aufgegeben worden."

References

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  1. ^ "Drosera L." International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-11-29.
  2. ^ Cheek, Martin (2001). "Drosera longifolia L. vs. Drosera intermedia Hayne and Drosera anglica Hudson" (PDF). Carnivorous Plant Newsletter. 30 (1): 29. Retrieved 29 November 2024.
  3. ^ "Drosera anglica Huds". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-12-02.
  4. ^ "Drosera intermedia Hayne". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-12-02.
  5. ^ "Drosophyllum lusitanicum Link". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-12-02.
  6. ^ a b c d e f Lowrie, Allen; Nunn, Richard; Robinson, Alastair; Bourke, Greg; McPherson, Stewart; Fleischmann, Andreas (2017). Drosera of the World Vol. 1. Poole, Dorset, England: Redfern Natural History Productions. ISBN 978-1-908787-16-3.
  7. ^ de Candolle, A. P. (1824). Prodromus systematis naturalis regni vegetabilis, sive, Enumeratio contracta ordinum generum specierumque plantarum huc usque cognitarium, juxta methodi naturalis, normas digesta. Vol. 1. pp. 317–319. doi:10.5962/bhl.title.286. Retrieved 29 November 2024.
  8. ^ Lehmann, Johann Georg Christian (1844). Novarum et minus cognitarum stirpium pugillus I-X, addita enumeratione plantarum omnium in his pugillis descriptarum: vol. 8. Hamburg: Typis J.A. Meissneri. p. 44. Retrieved 30 November 2024.
  9. ^ "Sondera preissii Lehm". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2024-11-29.
  10. ^ "Sondera macrantha (Endl.) Lehm". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2024-11-29.
  11. ^ "Sondera Lehm". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2024-11-29.
  12. ^ Planchon, J. E. (1848). "Sur les Droséracées". Annales des Sciences Naturelles, Botanique. 3 (9): 91–95. Retrieved 29 November 2024.
  13. ^ Bentham, George; Mueller, Ferdinand (1864). Flora Australiensis: A description of the plants of the Australian territory. Volume 2. London: Lovell Reeve & Co. p. 453. Retrieved 1 December 2024.
  14. ^ Bentham, G.; Hooker, J. D. (1865). Genera Plantarum: ad exemplaria imprimis in Herberiis Kewensibus servata definita. Vol. 1, Part 2. London: Lovell Reeve & Co., Williams & Norgate. p. 662. Retrieved 1 December 2024.
  15. ^ a b Stein, Berthold (1886). "Droseraceae". Gartenflora. 35: 654–665. Retrieved 30 November 2024.
  16. ^ a b Drude, O (1888). Engler, Adolf, Krause, Kurt, Pilger, R., Prantl, Karl (eds.). Droseraceae. In: Die Natürlichen Pflanzenfamilien nebst ihren Gattungen und wichtigeren Arten, insbesondere den Nutzpflanzen, unter Mitwirkung zahlreicher hervorragender Fachgelehrten begründet. W. Engelmann. pp. 270–272. doi:10.5962/bhl.title.4635.
  17. ^ a b c d e f g Diels, Ludwig (1906). Droseraceae In: Engler, A. Das Pflanzenreich: Regni vegetabilis conspectus. Heft 26. Leipzig: W. Engelman. Retrieved 30 November 2024.
  18. ^ a b c d e Fleischmann, Andreas; Cross, Adam; Gibson, Robert; Gonella, Paulo; Dixon, Kingsley (2018). Systematics and taxonomy of Droseraceae. In: Carnivorous Plants: Physiology, ecology and evolution. Oxford University Press. pp. 45–57. ISBN 9780198779841. Retrieved 22 September 2024.
  19. ^ "Drosera sect. Arachnopus Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-09-27.
  20. ^ Brittnacher, John (2014). "The Drosera indica Species Complex". International Carnivorous Plant Society. Retrieved 27 September 2024.
  21. ^ a b c d e Fleischmann, Andreas; Gonella, Paulo; Rivadavia, Fernando (2018). "A new sectional name for the Brazilian tetraploid clade of Drosera subgenus Drosera" (PDF). Carnivorous Plant Newsletter. 47 (1): 4–9. doi:10.55360/cpn471.af718. Retrieved 29 September 2024.
  22. ^ Fleischmann, Andreas; Rivadavia, Fernando; Gonella, Paulo (2018). "Erratum" (PDF). Carnivorous Plant Newsletter. 47 (4): 135. Retrieved 29 September 2024.
  23. ^ a b Rivadavia, Fernando; Kondo, Katsuhiko; Kato, Masahiro; Hasebe, Mitsuyasu (2003). "Phylogeny of the sundews, Drosera (Droseraceae), based on chloroplast rbcL and nuclear 18S ribosomal DNA sequences". American Journal of Botany. 90 (1): 123–130. doi:10.3732/ajb.90.1.123. Retrieved 23 November 2024.
  24. ^ "Drosera sect. Prolifera C.T.White". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-04.
  25. ^ Nunn, Richard; Bourke, Greg (2017). "An account of Drosera section Prolifera" (PDF). Carnivorous Plant Newsletter. 46 (3): 92–100. Retrieved 4 October 2024.
  26. ^ Mathieson, Michael T; Thompson, Simon L (2020). "Drosera buubugujin M.T.Mathieson (Droseraceae, Drosera section Prolifera C.T.White), a spectacular new species of sundew from the Cape York Peninsula bioregion" (PDF). Austrobaileya. 10 (4): 549–557. Retrieved 4 October 2024.
  27. ^ a b c d e f Lowrie, Allen; Robinson, Alastair; Nunn, Richard; Rice, Barry; Bourke, Greg; Gibson, Robert; McPherson, Stewart; Fleischmann, Andreas (2017). Drosera of the World, Vol. 2. Poole, Dorset, England: Redfern Natural History Productions. ISBN 978-1-908787-17-0.
  28. ^ "Drosera sect. Psychophila Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-05.
  29. ^ "Drosera sect. Ptycnostigma Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-13.
  30. ^ "Drosera cistiflora". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 15 October 2024.
  31. ^ Marchant, N. G.; Ashton, H. I.; George, A. S. (1982). Droseraceae. In: A. S. George [ed.] Flora of Australia, Lecythidales to Batales, vol. 8. Canberra, Australia: Australian Government Printing Service. pp. 9–66.
  32. ^ a b c Seine, Rudiger; Barthlott, Wilhelm (1994). "Some proposals on the infrageneric classification of Drosera L." Taxon. 43 (4): 583–89. doi:10.2307/1223544. Retrieved 13 October 2024.
  33. ^ "Drosera sect. Stelogyne Diels". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-13.
  34. ^ a b Schlauer, Jan (1996). "A dichotomous key to the genus Drosera L. (Droseraceae)" (PDF). Carnivorous Plant Newsletter. 25 (3): 67–88. doi:10.55360/cpn253.js950. Retrieved 13 October 2024.
  35. ^ "Drosera sect. Thelocalyx Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-05.
  36. ^ "Drosera sect. Bryastrum Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-05.
  37. ^ "Drosera sect. Coelophylla Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-05.
  38. ^ "Drosera sect. Ergaleium A.P. de Candolle". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-22.
  39. ^ Fleischmann, Andreas (2022). "The huge scientific footprint of Allen James Lowrie (1948-2021)" (PDF). Carnivorous Plant Newsletter. 51 (1): 22–39. doi:10.55360/cpn511.af192. Retrieved 24 November 2024.
  40. ^ "Drosera sect. Lasiocephala Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-05.
  41. ^ Nunn, Richard; Lowrie, Allen (2020). "An account of Drosera section Lasiocephala" (PDF). Carnivorous Plant Newsletter. 50 (3): 118–132. doi:10.55360/cpn503.rn308. Retrieved 5 October 2024.
  42. ^ "Drosera sect. Phycopsis Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-05.
  43. ^ "Drosera binata". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 5 October 2024.
  44. ^ "Drosera sect. Arcturia Planch". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 2024-10-17.
  45. ^ Lowrie, Allen; Conran, John (2014). "Drosera murfetii (Droseraceae): a new species from Tasmania, Australia" (PDF). Journal of the Adelaide Botanic Gardens. 27: 7–21. Retrieved 17 October 2024.
  46. ^ Barnard, Hendre (2022). "Hunting the King - Drosera regia trip report" (PDF). Carnivorous Plant Newsletter. 51 (4): 204–206. doi:10.55360/cpn514.hb100. Retrieved 17 October 2024.
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