Myosotis rakiura

Myosotis rakiura
Myosotis rakiura in flower
Conservation status
Naturally Uncommon (NZ TCS) [1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Boraginales
Family:	Boraginaceae
Genus:	Myosotis
Species:	M. rakiura
Binomial name
Myosotis rakiura L.B.Moore [2]
Synonyms [3]
Myosotis albida(Kirk) Cheeseman ex Cockayne

Myosotis rakiura is a species of flowering plant in the family Boraginaceae, endemic to southern South Island and Stewart Island/Rakiura of New Zealand. Joseph Beattie Armstrong described the species in 1881. Plants of this species of forget-me-not are perennial rosettes which form loose tufts or clumps, with ebracteate, erect inflorescences, and white corollas with exserted stamens.

Taxonomy and etymology

Myosotis rakiura is in the plant family Boraginaceae and was described as M. capitata var. albiflora in 1881 by Joseph Beattie Armstrong . ^{[4] [5] [6] [7]} Lucy Moore gave it a new name, M. rakiura, when she recognized it at the species level, because M. albiflora Banks & Sol. ex Hook.f. was already validly published for a southern South American species. ^{[4] [5]}

Myosotis rakiura is morphologically similar to other ebracteate-erect species, especially the New Zealand subantarctic island endemic species, M. capitata . ^[5] Myosotis rakiura can be distinguished from M. capitata by the following characters: white corollas, the presence of retrorse trichomes on many plant parts (e.g. the underside of the rosette leaves), and fully exserted anthers. ^[5]

The lectotype specimen of Myosotis rakiura was collected from Stewart Island/Rakiura by James West Stack and is lodged at Manaaki Whenua - Landcare Research Allan Herbarium (CHR 635645), ^[8] where there is also an isolectotype (CHR 635646). ^{[9] [5]}

The specific epithet, rakiura, is derived from the Ngāi Tahu name in te reo Māori for Stewart Island (Rakiura), which can be translated as ‘glowing sky’. ^[5]

Phylogeny

Myosotis rakiura was shown to be a part of the monophyletic southern hemisphere lineage of Myosotis in phylogenetic analyses of standard DNA sequencing markers (nuclear ribosomal DNA and chloroplast DNA regions). ^{[10] [11]} Within the southern hemisphere lineage, species relationships were not well resolved. The two sequenced individuals of M. rakiura grouped with a mixture of bracteate-prostrate and ebracteate-erect species in different analyses. ^{[10] [11]}

Description

Myosotis rakiura plants are single rosettes that often grow together to form loose tufts or clumps. The rosette leaves have petioles 5–40 mm long. The rosette leaf blades are 19–62 mm long by 7–21 mm wide (length: width ratio 2.0–5.3: 1), oblanceolate or sometimes narrowly ovate, widest at or above the middle (rarely below the middle), with an obtuse apex. The upper surface is densely covered in mostly flexuous, patent to erect, antrorse (forward-facing) hairs that are oriented oblique to the mid vein. The hairs on the edges of the leaf are similar but mostly erect, and the hairs on the underside of the leaf are also similar but mostly retrorse (backward-facing) and appressed to patent. Each rosette has 1–10 erect, once- or twice-branched, ebracteate inflorescences that are up to 300 mm long and are bifurcating in a forked 'V' shape near the tips. The cauline leaves are similar to the rosette leaves but smaller with shorter petioles, and decrease in size toward the tip. Each inflorescence has up to 210 flowers, each borne on a pedicel up to 4 mm long at fruiting, and each without a bract. The calyx is 3–5 mm long at flowering and 3–7 mm long at fruiting, lobed to half to three-quarters of its length, and densely covered in mostly antrorse (some retrorse near the base), patent to erect, mostly flexuous hairs. The corolla is white, up to 9 mm in diameter, with a cylindrical tube, petals that are obovate, broadly obovate or very broadly obovate, and small yellow scales alternating with the petals. The anthers are fully exserted above the scales. The four smooth, shiny, medium to dark brown nutlets are 1.5–2.0 mm long by 0.9–1.4 mm wide and ovoid in shape. ^[5]

Flowering plants in coastal habitat on Stewart Island

The chromosome number of M. rakiura is unknown.

The pollen of M. rakiura is unknown.

It flowers from November–February and fruits from July–April., with the main flowering and fruiting period from December–January, fruiting July–April. ^[5]

Distribution and habitat

Myosotis rakiura is a forget-me-not endemic to coastal southern New Zealand, specifically Otago and Southland (South Island), Stewart Island/Rakiura, and Solander Island/Hautere from 0–130 m ASL. It is found on coastal cliffs and rocks, in shrubland, turf or grassland. ^[5]

Conservation status

The species is listed as At Risk - Naturally Uncommon on the most recent assessment (2017-2018) under the New Zealand Threatened Classification system for plants, with the qualifiers "Sp" (Sparse) and "RR" (Range Restricted). ^{[1] [5]}

Gallery

• 
  Plants in fruit
• 
  Side view of inflorescence
• 
  Rosette leaves
• 
  Top view of inflorescence, with close-up of flowers

References

1. Lange, Peter J. de; Rolfe, Jeremy R.; Barkla, John W.; Courtney, Shannel P.; Champion, Paul D.; Perrie, Leon R.; Beadel, Sarah M.; Ford, Kerry A.; Breitwieser, Ilse; Schönberger, Ines; Hindmarsh-Walls, Rowan (May 2018). "Conservation status of New Zealand indigenous vascular plants, 2017" (PDF). New Zealand Threat Classification Series. 22: 45. OCLC   1041649797.
2. Armstrong, Joseph Beattie (1881). Transactions and Proceedings of the New Zealand Institute. Vol. 13. p. 340.
3. "Myosotis rakiura L.B.Moore". Plants of the World Online . Royal Botanic Gardens, Kew . Retrieved 29 August 2022.
4. Moore, L.B. "Boraginaceae. In 'Flora of New Zealand'. (Ed. HH Allan) Vol. 1, pp. 806–833". (Government Printer: Wellington, New Zealand) floraseries.landcareresearch.co.nz. Retrieved 27 April 2022.
5. Meudt, Heidi (2021). "Taxonomic revision of five species groups of ebracteate-erect Myosotis (Boraginaceae) endemic to New Zealand, based on morphology, and description of new subspecies" . Australian Systematic Botany. 34 (3): 252–304. doi:10.1071/SB20028. S2CID   234771910.
6. "Myosotis rakiura". New Zealand Plant Conservation Network. Retrieved 27 August 2022.
7. Armstrong, Joseph Beattie (1881). Transactions and Proceedings of the New Zealand Institute. Vol. 13. p. 340.
8. "Lectotype of Myosotis rakiura". scd.landcareresearch.co.nz. Retrieved 27 August 2022.
9. "Isolectotype of Myosotis rakiura". scd.landcareresearch.co.nz. Retrieved 27 August 2022.
10. Winkworth, Richard C.; Grau, Jürke; Robertson, Alastair William; Lockhart, Peter J. (1 August 2002). "The origins and evolution of the genus Myosotis L. (Boraginaceae)" . Molecular Phylogenetics and Evolution. 24 (2): 180–193. doi:10.1016/S1055-7903(02)00210-5. PMID   12144755.
11. Meudt, Heidi; Prebble, Jessica M.; Lehnebach, Carlos Adolfo (7 November 2014). "Native New Zealand forget-me-nots (Myosotis, Boraginaceae) comprise a Pleistocene species radiation with very low genetic divergence" . Plant Systematics and Evolution. 301 (5): 1455–1471. doi:10.1007/S00606-014-1166-X. S2CID   14686750.

External links

• Myosotis rakiura occurrence data from Australasian Virtual Herbarium
• Media related to Myosotis rakiura at Wikimedia Commons