Taxonomic revision of the southern hemisphere pygmy forget-me-not group (Myosotis; Boraginaceae) based on morphological, population genetic and climate-edaphic niche modelling data Author Prebble, Jessica M. Author Symonds, V. Vaughan Author Tate, Jennifer A. Author Meudt, Heidi M. text Australian Systematic Botany 2022 2022-05-05 35 1 63 94 http://dx.doi.org/10.1071/sb21031 journal article 10.1071/SB21031 1446-5701 10903921 Myosotis antarctica subsp. traillii Kirk, Trans. & Proc. New Zealand Inst. 16: 373 (1884) Myosotis pygmaea var. traillii (Kirk) Cockayne, Veg. New Zealand 69, 72 and index (1921). Type citation : ‘ Sandy places on west coast of Stewart Island’ . Type : NEW ZEALAND , Rakiura / Stewart Island , sand hills , Mason Bay , 13 January 1882 , T. Kirk s.n. ( lecto [designated by L. B. Moore in H. H. Allan (Ed.), Fl. New Zealand 1: 815 (1961) ]: WELT SP002666 !) . Description Rosette plants with multiple prostrate branches up to 20 cm long. Rosette leaves 4–22; petioles 1.0–20.0 mm long; lamina margins and apex sometimes curling under, oblanceolate to obovate, 6.5–22.0 mm long, 3.0–15.0 mm wide (length:width ratio 1.0–2.5:1), bright to dull green to reddish-brown; apex obtuse, with hydathode on abaxial side; trichomes densely distributed, curved, antrorse, appressed to patent, appressed at the margins, distributed evenly (on leaf adaxial surface), and sparsely distributed, or on midrib only, or absent (on abaxial surface), (0.2–)0.4–0.7(–1.2) mm long, deciduous with age. Basal cauline leaves not subtending flowers, 1–5 per branch, lamina similar in size and shape to the rosette leaves, with petioles up to 5.4 mm ; distal cauline leaves subtending flowers up to 33 per branch, lamina 2.0–9.0 mm long, 1.0– 5.5 mm wide, usually sessile. Pedicels up to 0.9 mm long (flowering) or 1.6 mm long (fruiting). Calyx 1.0–3.0 mm long (flowering) increasing to (2.0–) 3.0– 5.5 mm long (fruiting), 1.5–5.5 mm wide at the top at fruiting, lobed to 1/3–2/3 the length of the calyx; with trichomes usually of uniform length but denser along ribs, sometimes of two lengths, longer and antrorse on ribs v. shorter and retrorse in between ribs and near the base (in other instances, the two length classes are not so obvious, and retrorse trichomes are not always present). Corolla (1.0–) 1.5–3.5 mm in diameter, white, cream, faucal scales yellow; corolla lobes 0.5–1.3 mm long (0.2–) 0.4–1.0 mm wide; corolla tube 0.5–1.0 mm wide at faucal scales, 1.2–2.4 mm long from base to faucal scales, narrow cylindric. Stamens 5, included; filaments attached below faucal scales, 0–0.3 mm long; anthers 0.4–0.8 mm long, subsessile; style (0.7–) 1.1–2.1 mm long (flowering) to 1.4–2.7 mm long (fruiting). Nutlets 4, 1.2–1.8 mm long, 0.8–1.2 mm wide. Illustration citations Fig. 8 ; Moore (1961 , p. 808), as M. pygmaea var. pygmaea ; Wilson (1994 , p. 245), as M. pygmaea var. pygmaea [with note ‘= M. antarctica var. traillii ’]; Webb and Simpson (2001 , p. 142), as M. pygmaea var. pygmaea ; Mark (2012 , p. 256), as Myosotis pygmaea . Distribution NEW ZEALAND : North Island : Auckland , Taranaki , Southern North Island ; South Island : Western Nelson , Canterbury , Otago , Southland ; Stewart Island : Rakiura; mostly coastal ( Fig. 8 ). Habitats Coastal turfs, sand dunes, fell fields, river terraces, and rock tors. Elevation from sea level to 250(–1500) m. Phenology Flowering August–April. Fruiting September–April. Peak flowering and fruiting December–January. Notes Identification . Plants of Myosotis antarctica subsp. traillii can be distinguished from M. glauca and M. antarctica subsp. antarctica on the basis of their curved, appressed to patent trichomes. Like M. antarctica subsp. antarctica , this subspecies can be separated from M. brevis because of its generally larger size, for example, corolla diameter of (1.0–) 1.5–4.0 mm, calyx length at flowering of (1.2–) 2.0–3.0(–3.5) mm long and nutlets of (1.0–) 1.2–1.9 mm long and (0.7–) 0.8–1.2 mm wide. Plants of M. antarctica subsp. traillii usually grow coastally ( Fig. 8 ), but 18 specimens collected from inland populations with curved, appressed to patent trichomes have been identified; these are the populations that reach the higher elevations indicated above. Taxonomic history . The name Myosotis antarctica subsp. traillii was first published by Kirk (1884) . The name was not often applied to herbarium specimens (although see CHR 357370 collected by L. Cranwell in 1940), and in the Flora of New Zealand treatment, Moore (1961) considered it to be a synonym of M. pygmaea . However, most of specimens identified as M. pygmaea do not match the type of the species (WELT SP004743!), which has flexuous trichomes (fig. 6 in Prebble et al . 2018 ). The names M. pygmaea Colenso and M. antarctica subsp. traillii were published in two different papers in the same volume but different issues of the same journal, and Moore (1961 , p. 815) noted the apparent similarities in the descriptions of these two taxa but did not discuss the differences in the trichomes between the two type specimens themselves. Thus, the epithet ‘pygmaea’ is unable to be used for this subspecies, because the type specimen for the name falls within the circumscription of the other subspecies, M. antarctica subsp. antarctica . In any case, M. pygmaea Colenso is an illegitimate name (see Discussion). The original description of M. antarctica subsp. traillii mentions the trichomes are ‘appressed’, which matches those plants generally identified as M. pygmaea in recent years. Furthermore, in nMDS analyses of morphological characters, the type of M. antarctica subsp. traillii clusters with all other specimens identified as ‘ M. pygmaea ’ apart from the type specimen of M. pygmaea (fig. 6 in Prebble et al . 2018 ). Fig. 8. Myosotis antarctica subsp. traillii photographs and distribution map. ( a ) Habit. ( b , d ) Rosette leaf tips: ( b ) adaxial and ( d ) abaxial sides. ( c ) Flower. ( e ) Nutlets. ( f ) Map of georeferenced herbarium specimens observed by J. M. Prebble (35). Whie scale bars: 2 mm; black scale bars: 1 mm. Photo credits: a , e by J. M. Prebble ( a : WELT SP100487, Tiwai Point, Southland, South Island; e : WELT SP104518, cultivated ex Mason Bay, Stewart Island). b, c © Te Papa by H. M. Meudt ( b : WELT SP090544, Manihi Rd, Taranaki, North Island; c : WELT SP090629, Hukanui, Gisborne, North Island; d : WELT SP090631, Waipuna, Gisborne, North Island). Additional characters identified by Moore (1961) as characteristic of Myosotis pygmaea var. pygmaea v . M. pygmaea var. drucei (e.g. protruding nutlets) were found to not vary significantly between these taxa (here called M. antarctica subsp. traillii and M. antarctica subsp. antarctica respectively). Given that there is only a single morphological character that distinguishes these two subspecies, the possibilities of not recognising them as distinct or recognising them at the rank of variety were considered. However, given that the morphological differentiation seen here is correlated with allopatry (i.e. inland v. coastal on the North and South Islands), it was decided that it was appropriate to recognise these taxa at subspecies rank (e.g. Hamilton and Reichard 1992 ; Meudt 2006 ; Stuessy 2009 ). Patterns in the data . All specimens of Myosotis antarctica subsp. traillii are united morphologically ( Prebble et al . 2018 ) but not genetically ( Prebble et al . 2019 ). In the nMDS analyses of morphological characters measured on herbarium specimens, all samples of M. antarctica subsp. traillii group together (fig. 6 in Prebble et al . 2018 , identified as M. pygmaea , excluding the M. pygmaea type specimen). Qualitative morphological characters found in both the herbarium and growth-room datasets distinguish M. antarctica subsp. antarctica from M. glauca and M. antarctica subsp. traillii , i.e. trichomes that are curved and appressed to patent on the leaf blade and leaf margins. In the Structure analyses of microsatellite data, not all populations of Myosotis antarctica subsp. traillii form a cluster (fig. 3 in Prebble et al . 2019 , as M. pygmaea ), and neither do these populations group together in the NeighbourNet network (fig. 5 in Prebble et al . 2019 , as M. pygmaea ). There is geographic structuring present in the genetic data, whereby populations that grow closer together are often more closely related, although this pattern is not universal. Five populations from Western Nelson in the South Island and coastal Taranaki in the North Island are united genetically (WELT SP100460, WELT SP100462, WELT SP090542, WELT SP090544 and WELT SP090540); these land areas would have been connected during the last glacial maxima ( Lewis et al . 1994 ); so, this can be interpreted as a geographic pattern. No morphological characters were found to unite these five populations. Pollen morphology . Pollen of Myosotis antarctica subsp. traillii has the M. australis morphology type , the most common pollen type for bracteate-prostrate species of Myosotis ( Meudt 2016 ) and the ebracteate-erect species sampled so far ( Meudt et al . 2020 ). Representative specimens were recovered in Cluster 1 in an nMDS analyses (see fig. 2 in Meudt 2016 ), along with other specimens with pollen of the M. australis morphology type . Chromosome number . A count from one individual (identified as Myosotis pygmaea ) has been undertaken, i.e. n = 22, AK 303514 ( Murray and de Lange 2013 ). Recommended conservation status Myosotis antarctica subsp. traillii is listed as At Risk – Declining B(1) with the qualifier Sparse in de Lange et al . (2018 , as M. pygmaea ). Taking into account evidence of census size and small area of occupation, we recommend the conservation status of M. antarctica subsp. traillii be amended to Threatened – Nationally Vulnerable with the qualifier Sparse (see Table 6 for more details). Threats . It has been recognised that Myosotis antarctica subsp. traillii is declining ( de Lange et al . 2018 , as M. pygmaea ). As is the case with M. brevis (see above), the North Island populations are most at risk, as none of them inhabits DOCmanaged land, and the same pressures of cliff-edge erosion and farmland proximity were seen at coastal Taranaki populations (i.e. WELT SP090540, WELT SP090542, and WELT SP090544). Two populations previously collected from the Wairarapa and Taranaki coasts (e.g. CHR 245912 and WELT SP095607) were not relocated when searching for them in 2011. The most genetically distinct M. antarctica subsp. traillii populations that could be considered a priority for conservation are from the North Island Hawke’s Bay region (WELT SP090629, WELT SP090631 and WELT SP090634), where they grow on rock outcrops on privately owned farmland. Representative specimens ( 94 specimens examined) NEW ZEALAND . North Island: Taranaki : Arawhata Rd end, 5 Oct. 2011 , H. M. Meudt HMM310 , J. M. Prebble , C. Ogle , E. King , K. Eaton , G. La Cock , B. Clarkson , M. Parsons & B. Hartley (WELT SP090542); Manihi Rd end, 6 Oct. 2011 , H. M. Meudt HMM312 , J. M. Prebble , E. King , K. Eaton , B. Clarkson , & B. Hartley (WELT SP090544); Opunake water treatment ponds, 5 Oct. 2011 , H. M. Meudt HMM309 , J. M. Prebble , C. Ogle , E. King , K. Eaton , G. La Cock , B. Clarkson , M. Parsons & B. Hartley (WELT SP090540); Puketapu Rd end, Nov. 1971 , A. P. Druce s.n. ( CHR 245912). Southern North Island: Te Waka Range, Jan. 1972 , A. P. Druce s.n. ( CHR 246383); Waipuna Station, 13 Dec. 2011 , H. M. Meudt HMM333 , J. M. Prebble , M. Thorsen and P. Carswell (WELT SP090631). South Island: Western Nelson , Cape Farewell, Whararkiki Beach, Nov. 1971 , A. P. Druce s.n. ( CHR 245193); Gordon’s Knob, 5 Feb. 1910 , D. Petrie s.n. (WELT SP002650A); Hoary Head, 21 Jan. 2013 , J. M. Prebble JMP13007 (WELT SP100472); north of Heaphy River, Nov. 1977 , A. P. Druce s.n. ( CHR 313155); near Sandhill Ck river mouth, 26 Jan. 2013 , J. M. Prebble JMP13022 (WELT SP100460); ridge track to Mt Arthur, 22 Jan. 2013 , J. M. Prebble JMP13009 (WELT SP100477); south of Paturau River mouth, 26 Jan. 2013 , J. M. Prebble JMP13020 (WELT SP100462). Otago : Chrystall’s Beach, 27 Dec. 2004 , M. Thorsen s.n. (WELT SP089920); Eyre Creek, headwaters of Little Jungle Creek, 6 Jan. 1987 , A. F. Mark s.n. ( OTA 044898). Southland , Oraka Point, 17 Jan. 2000 , B. D. Rance s.n. ( CHR 541256); Omaui, Three Sisters Dune, 8 Jan. 1995 , P. J. de Lange s.n. ( AK 231694); Tiwai Point, 25 Feb. 2013 , J. M. Prebble JMP13031 & K. Pilkington (WELT SP100487). Stewart Island : Rakiura: Mason Bay, 13 Jan. 1882 , T. Kirk s.n. ( AK 7443).