Myosotis saxosa

Myosotis saxosa
flowering plants of Myosotis saxosa
Conservation status
Nationally Critical (NZ TCS) [1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Boraginales
Family:	Boraginaceae
Genus:	Myosotis
Species:	M. saxosa
Binomial name
Myosotis saxosa Hook.f. [2]

Myosotis saxosa is a species of flowering plant in the family Boraginaceae, endemic to the North Island of New Zealand. Joseph Dalton Hooker described the species in 1853. Plants of this species of forget-me-not are perennial rosettes with ebracteate inflorescences and white corollas with stamens that are exserted.

Taxonomy and etymology

Myosotis saxosa Hook.f. is in the plant family Boraginaceae. ^[3] The species was originally described in 1853 by Joseph Dalton Hooker in Flora Novae-Zelandiae . ^{[4] [2]} Hooker transferred it to Exarrhena saxosa (Hook.f.) Hook.f. in 1867 on the basis of its exserted stamens, ^[5] but this name is a homotypic synonym because that genus is no longer recognised. ^[4]

The most recent treatment of this species was done by Lucy B. Moore in the Flora of New Zealand. ^[4]

The type specimen of Myosotis saxosa was collected by William Colenso at Titiokura, Hawkes Bay, North Island, New Zealand, and is lodged at Kew Herbarium (K000787881). ^{[6] [4]}

Cheeseman ^[7] made the following distinction between M. amabilis and M. saxosa:

"Rather stout, 3–9 in. high. Leaves 1–2½ in., linear-obovate or obovate-spathulate, coriaceous, hispid on both surfaces. Racemes many-flowered. Flowers large, white, ½ in. diam.........17. M. amabilis Small, stout, 2–3 in. high. Leaves ½–¾ |in., oblong-spathulate, hispid and hoary on both surfaces. Racemes few flowered. Flowers small . . . . . . . . 18. M. saxosa." ^[7]

Some sources consider M. amabilis to be a synonym of M. saxosa, ^[3] whereas others recognise two distinct species. ^[8] Whether M. amabilis and M. saxosa are one species or two is an outstanding taxonomic question that requires further study. ^[9]

Phylogeny

Myosotis saxosa 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) of New Zealand Myosotis. ^[10] Within the southern hemisphere lineage, species relationships were not well resolved. ^{[10] [11]} The three individuals of M. saxosa sampled from the Maungaharuru Range that were included in the study were monophyletic or closely related, and grouped with other North Island species of Myosotis. ^[10]

Description

Myosotis saxosa plants are rosettes. The rosette leaves have petioles that are about as long as the leaf blades. The rosette leaves are about 20–30 mm long by 5–10 mm wide (length: width ratio c. 2–6: 1), and the leaf blade is broad-ovate to obovate, widest below, at or above the middle, with an apiculate apex. Both surfaces of the leaf are uniformly and sparsely to densely covered in patent to erect hairs. On the upper surface of the leaf, these hairs are always antrorse (forward-facing) whereas on the lower surface, they can be either antrorse or mostly retrorse (backward-facing). Each rosette has several ascending to erect, ebracteate inflorescences that are up to 70 mm long. The cauline leaves are similar to the rosette leaves, but are smaller, elliptic, and subacute to acute, and have hairs similar to the rosette leaves but more appressed. The flowers are about 12 per inflorescence, and each is borne on a short pedicel, without a bract. The calyx is about 5 mm long at flowering and fruiting, lobed to one-half tor more of its length, and densely covered in appressed hairs, as well as some patent hairs, all of which are mostly antrorse. The corolla is white and 7–13  mm in diameter, with a cylindrical tube, and small scales alternating with the petals. The anthers are exserted, surpassing the faucal scales. The nutlets are c. 2.2 mm long by 1.3 mm wide. ^[4]

The pollen of Myosotis saxosa is unknown.

The chromosome number of M. saxosa is 2n = 22. ^[12]

Flowering November–Jan and fruiting November–March. ^[3]

Distribution and habitat

Myosotissaxosa is a forget-me-not originally collected from Titiokura, Hawkes Bay, North Island, New Zealand. ^[4] Some specimens collected in other areas Hawkes Bay, East Cape (Hikurangi) and even on the South Island have been variously identified as M. amabilis or M. saxosa, ^{[13] [3]} and the two species require taxonomic revision. ^[9] Recent efforts to relocate plants at some North Island localities have been unsuccessful. ^[9]

Conservation status

Myosotis saxosa is listed as Threatened – Nationally Critical" with the qualifiers Data Poor (DP), Range Restricted (RR), Sparse (Sp) and Stable (St) on the most recent assessment (2017-2018) under the New Zealand Threatened Classification system for plants. ^[1]

Gallery

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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. Hooker, Joseph Dalton (1853). 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. Vol. 2. London: Reeve Brothers. p. 202.
3. "Myosotis saxosa". New Zealand Plant Conservation Network. Retrieved 28 July 2023.
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. Hooker, Joseph Dalton (1 January 1867). Handbook of the New Zealand flora : a systematic description of the native plants of New Zealand and the Chatham, Kermadec's, Lord Auckland's, and Macquarrie's islands.
6. "Type of Myosotis saxosa Hook.f. on JSTOR". plants.jstor.org. Retrieved 28 July 2023.
7. Cheeseman, T. F. (1906), Manual of the New Zealand flora, J. Mackay, Govt. Printer, pp. 468–469, doi:10.5962/BHL.TITLE.12003, OCLC   4397520, OL   234533M, Wikidata   Q51396409
8. "Flora of New Zealand | Taxon Profile | Myosotis amabilis". www.nzflora.info. Retrieved 4 July 2023.
9. "Searching for rare forget-me-nots with North Island iwi". Te Papa’s Blog. 4 June 2021. Retrieved 4 July 2023.
10. Meudt, Heidi; Prebble, Jessica; Lehnebach, Carlos A. (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.
11. Richard Winkworth; Jürke Grau; Alastair Robertson; Peter Lockhart (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. Wikidata   Q30707919.
12. Dawson, Murray (1 January 2000). "Index of chromosome numbers of indigenous New Zealand spermatophytes". New Zealand Journal of Botany. 38: 47–150.
13. "Myosotis amabilis Cheeseman". www.gbif.org. Retrieved 4 July 2023.

External links

• Myosotis saxosa occurrence data from Australasian Virtual Herbarium