Rhizanthella speciosa

Rhizanthella speciosa is a species of flowering plant in the orchid family and is endemic to Barrington Tops in New South Wales. It is a mycoheterotrophic herb that spends its entire life cycle, including flowering, at or below the soil surface. As at September 2020, R. speciosa has not yet been accepted as a valid name by the World Checklist of Selected Plant Families or the Australian Plant Census.

Rhizanthella speciosa
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Diurideae
Genus: Rhizanthella
Species:
R. speciosa
Binomial name
Rhizanthella speciosa

Description

Rhizanthella speciosa is a leafless, sympodial herb with a horizontal rhizome and underground stem probably similar to that of R. slateri. From October to early November, the plant produces a flower head 15–30 mm (0.59–1.18 in) wide containing fifteen to thirty-five flowers about 5 mm (0.20 in) in diameter. The flower heads are bright mauve to pinkish purple and are surrounded by sixteen to eighteen overlapping, fleshy, egg-shaped to triangular bracts 10–12 mm (0.39–0.47 in) long and 3–4 mm (0.12–0.16 in) wide. After pollination, the flower produces a fleshy, narrow cylindrical drupe that is pinkish to light maroon when ripe.[1][2]

Taxonomy and naming

This species of underground orchid was discovered in 2016 by scientific illustrator Maree Elliot and formally described in 2020 by Mark Clements and David Jones in the journal Lankesteriana from material collected in Barrington Tops National Park. The specific epithet speciosa is from the Latin speciosus meaning "showy" or "splendid".[2][3][4]

Distribution and habitat

Rhizanthella speciosa was found under dense leaf litter in tall wet sclerophyll forest of the Barrington Tops National Park with Sydney blue gum, tallowood, and turpentine, and a well-developed rainforest subcanopy with Trochocarpa laurina and Synoum glandulosum.[1][2]

Conservation status

As of 2020, only fifty plants in a single locality are known. The habitat where it grows is widespread, but searches have not uncovered other populations. Thus the species meets the "critically endangered" definition. The population's exact location is kept unpublished for its protection.[2][4]

References
  1. "Rhizanthella speciosa". Royal Botanic Garden Sydney. Retrieved 28 September 2020.
  2. Clements, Mark A.; Jones, David L. (30 July 2020). "Notes on Australasian Orchids 6: A new species of Rhizanthella (Diurideae, subtribe Prasophyllinae) from Eastern Australia". Lankesteriana. 20 (2): 221–227. doi:10.15517/lank.v20i2.43271.
  3. "Rhizanthella speciosa". APNI. Retrieved 28 September 2020.
  4. Allen, Craig (13 September 2020). "To protect this rare underground orchid, researchers are keeping its location top secret". Australian Broadcasting Corporation. Retrieved 28 September 2020.
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