Myosotis arnoldii
Herbarium specimen of Myosotis arnoldii plant collected in 2013 WELT SP100473

Naturally Uncommon (NZ TCS)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Boraginales
Family: Boraginaceae
Genus: Myosotis
Species:
M. arnoldii
Binomial name
Myosotis arnoldii

Myosotis arnoldii is a species of flowering plant in the family Boraginaceae, endemic to the South Island of New Zealand. Lucy Moore described the species in 1961. Plants of this species of forget-me-not are perennial rosettes with ebracteate inflorescences, corollas ranging from yellow to dark purple, and stamens that are wholly exserted.

Description

Myosotis arnoldii plants are rosettes. The rosette leaves have broad petioles that difficult to distinguish from the leaf blades. The rosette leaves are 30–70 mm long by 5–9 mm wide (length: width ratio ca. 3–7: 1), linear-spathulate or oblanceolate, and widest at or above the middle, with an subacute to obtuse apex. Both surfaces of the leaf are uniformly and densely covered in straight, appressed, white hairs that completely cover the underlying leaf surface. Each rosette has several erect, ebracteate inflorescences that are up to 180 mm long. The cauline leaves are similar to the rosette leaves, but smaller, are narrow-oblong and subacute, and have hairs similar to the rosette leaves.

The flowers are many per inflorescence, and each is borne on a short pedicel, each with a bract. The calyx is c. 8 mm long at flowering and fruiting, lobed to one-half of its length, and densely covered in straight, appressed antrorse hairs, as well as some erect hooked hairs near the base. The corolla is yellow to dark purple, "deeply coloured", and about 8–10 mm in diameter, with a cylindrical tube, and small scales alternating with the petals. The anthers are exserted with the anthers surpassing the faucal scales. The nutlets were not described.[3] Flowering occurs between October to January and fruiting from December to May.[3]

Taxonomy

Myosotis arnoldii is in the plant family Boraginaceae and was originally described in 1961 by Lucy Moore in the Flora of New Zealand.[2][3]

The original specimens (isotypes) of this species were collected by Arnold Wall from "Ben More, Ure River, Marlborough", South Island, New Zealand.[2] The specimens collected by Wall are housed are lodged at the Museum of New Zealand Te Papa Tongarewa, Wellington (herbarium WELT).[2][4][5]

The specific epithet, arnoldii, is named after Arnold Wall (1869 – 1966), a New Zealand botanist who made the first collections.[2]

Lucy Moore suggested that Myosotis arnoldii is morphologically most similar to M. angustata and M. macrantha based on habit and leaves, and to M. albosericea based on the very dense covering of white, appressed hairs on its vegetative parts including the rosette and stem leaves, which completely obscure the epidermis.[2] These hairs are antrorse (forward facing), straight, and on the leaf are oriented parallel to the midrib. The only other New Zealand species with such hairs is Myosotis albosericea, endemic to southern South Island, New Zealand.[6]

Phylogeny

No individuals of M. arnoldii were included in phylogenetic analyses of standard DNA sequencing markers (nuclear ribosomal DNA and chloroplast DNA regions) of New Zealand Myosotis.[7][8] In those studies, within the southern hemisphere lineage, species relationships were not well resolved.[7][8]

Three individuals from one population of M. arnoldii were also genotyped in a study that developed microsatellite DNA markers for another species group of New Zealand Myosotis.[9][10] The individuals of M. arnoldii included showed a high number of alleles that cross-amplified at most of the microsatellite loci.[10]

Distribution and habitat

Myosotis arnoldii is a forget-me-not is known to occur in two disjunct populations in the northern part of the South Island, New Zealand.[3][11] This species grows on cliff faces and other rocky habitats on marble substrates on Hoary Head, North West Nelson and on limestone substrates at its type locality in the Chalk Range, Marlborough.[3][2][12]

Myosotis arnoldii is likely to be an outcrossing species, with plants requiring a pollinating vector to achieve pollination and seed set.[11]

Conservation status

Myosotis arnoldii is listed as At Risk – Naturally Uncommon with the qualifiers Data Poor (DP) and Range Restricted (RR) on the most recent assessment (2017-2018) under the New Zealand Threatened Classification system for plants.[1]

References

  1. 1 2 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. 1 2 3 4 5 6 7 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.
  3. 1 2 3 4 5 "Myosotis arnoldii". New Zealand Plant Conservation Network. Retrieved 26 July 2023.
  4. ↑ "Myosotis arnoldii isotype | Collections Online - Museum of New Zealand Te Papa Tongarewa". collections.tepapa.govt.nz. Retrieved 26 July 2023.
  5. ↑ "Myosotis arnoldii isotype | Collections Online - Museum of New Zealand Te Papa Tongarewa". collections.tepapa.govt.nz. Retrieved 27 July 2023.
  6. ↑ 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.
  7. 1 2 Meudt, Heidi M.; Prebble, Jessica M.; Lehnebach, Carlos A. (1 May 2015). "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. ISSN 2199-6881. S2CID 254048318.
  8. 1 2 Winkworth, Richard C; Grau, Jürke; Robertson, Alastair W; 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. ISSN 1055-7903. PMID 12144755.
  9. ↑ Prebble, Jessica; Tate, Jennifer Alane; Meudt, Heidi; Symonds, Vaughan (9 June 2015). "Microsatellite markers for the New Zealand endemic Myosotis pygmaea species group (Boraginaceae) amplify across species". Applications in Plant Sciences. 3 (6). doi:10.3732/APPS.1500027. PMC 4467761. PMID 26082880.
  10. 1 2 Prebble, Jessica; Meudt, Heidi; Tate, Jennifer Alane; Symonds, Vaughan (1 August 2019). "Comparing and co‐analysing microsatellite and morphological data for species delimitation in the New Zealand native Myosotis pygmaea species group (Boraginaceae)". Taxon. 68 (4): 731–750. doi:10.1002/TAX.12096.
  11. 1 2 Mary Brandon, Andrea (2001). Breeding systems and rarity in New Zealand Myosotis (PhD thesis). Massey University.
  12. ↑ "Calcareous cliffs, scarps and tors". Manaaki Whenua. Retrieved 26 July 2023.
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