Ranunculus pinguis

Ranunculus pinguis is a dark green, fleshy-leaved buttercup with relatively large, short-stalked flowers and narrow stiff yellow petals that grows in tufts. It is an endemic species of New Zealand on the Auckland and Campbell Islands that flowers from December to January and sets seeds between February and April.[4][5]

Ranunculus pinguis
Ranunculus pinguis

Naturally Uncommon (NZ TCS)[1]
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Ranunculales
Family: Ranunculaceae
Genus: Ranunculus
Species:
R. pinguis
Binomial name
Ranunculus pinguis
Synonyms
  • R. pinguis var. pilosus
  • R. pinguis var. rhombifolius [4]

Etymology

The generic name Ranunculus is the diminutive of the Latin rana frog (little frog) and probably refers to the wet location where some buttercup species live together with frogs. The species epithet pinguis is Latin and means thick or fat.[6][7]

Description

Ranunculus pinguis is a tufted perennial of 5–25 cm high, with a stout rhizome. The leaves are stalked, with fleshy, glabrous or hairy blades of 2–8 cm that are narrowly diamond to kidney shaped, and shallowly incised to form three to five, or sometimes seven lobes, and a margin that is often with few large rounded teeth (or crenate). The solitary flowers are 2–3 cm in diameter. The pedicels are erect and usually hairy (pilose) at least in the upper half. The sepals are spread out and hairy. The five to ten yellow, narrow spoon-shaped petals usually have a single but occasionally three naked nectaries, about ½ cm above the base of the petal. The receptacle is glabrous, carrying numerous single and not fused carpels. These develop into dry, one-seeded fruits (or achenes) that are not flattened, mostly without hair, but sometimes pilose, with a body of 1½–2 mm and a straight beak of about 2 mm long.[4] The species has forty eight chromosomes (2n=48).[8]

Distribution and ecology

Ranunculus pinguis is not uncommon on Campbell Island and it grows among rocks from near sea-level to the peak of the hills. It usually grows where sheep cannot reach it. On the Auckland Islands it is common among rocks, but also fully exposed along the ridgeline in moist stony soil and along the higher limit of the grasslands on peat. In well-sheltered situations plants have large leaves without hair, as opposed to exposed plants.[5]

Taxonomy
Plate I[3] from the Flora of Lord Auckland and Campbell's Islands

There are some differences between the populations on both archipelagos. Auckland specimens often have somewhat narrowly orbicular hairless leaves, and more numerous and larger petals that regularly carry three nectarines. Campbell plants on the other hand often have round to kidney-shaped leaves covered by short but very fine silky hairs. Both populations vary in these characteristics and there is no reason to separate them taxonomically.[5] Genetic analysis shows that R. pinguis is sister to a group consisting of R. gunnianus, R. pachyrrhizus, R. sericophyllus and R. viridis.[8]

Conservation status

In both 2009 and 2012 it was deemed to be "At Risk - Naturally Uncommon" under the New Zealand Threat Classification System,[7] and this New Zealand classification was reaffirmed in 2018, due to its restricted range.[1]

References
  1. de Lange, P.J.; Rolfe, J.R.; Barkla, J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.M.; Ford, K.A.; Breitwieser, I.; Schönberger, .; Hindmarsh-Walls, R. (2018-05-01). "Conservation status of New Zealand indigenous vascular plants, 2017" (PDF). New Zealand Threat Classification Series. 22: 47. OCLC 1041649797.CS1 maint: numeric names: authors list (link)
  2. "Ranunculus pinguis Hook.f. | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 2020-02-20.
  3. Hooker, J.D. (1844). "Ranunculus pinguis". The botany of the Antarctic voyage of H.M. discovery ships Erebus and Terror in the Years 1839-1843 :under the command of Captain Sir James Clark Ross. 1: 3. Plate I
  4. Webb; et al. (1988). Flora of New Zealand. 4. cited on "Ranunculus pinguis Hook.f." Flora of New Zealand.
  5. F.J.F. Fischer; J.B. Hair (1963). "The Ranunculi of the subantarctic islands of New Zealand". New Zealand Journal of Botany. 1 (3): 325–335. doi:10.1080/0028825X.1963.10429003.
  6. "pinguis". Latin Dictionary.
  7. "Ranunculus pinguis | New Zealand Plant Conservation Network". nzpcn.org.nz. Retrieved 2020-02-20.
  8. C.A. Lehnebach (2008). Phylogenetic and Affinities, Species Delimitation and Adaptive Radiation of New Zealand Ranunculus, thesis (PDF). Palmerston North, New Zealand: Massey University. pp. 21–22.
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