Two new species of forget-me-nots ( Myosotis, Boraginaceae) from New Zealand

Abstract Two new species of forget-me-nots, Myosotis chaffeyorum C.A.Lehnebach sp. nov. and Myosotis mooreana C.A.Lehnebach sp. nov. are described and illustrated. These species are endemic to New Zealand and restricted to the mountains of north-west Nelson (South Island). Both species are uncommon and Myosotis mooreana is known from the type locality only. Their conservation status is rated as “Nationally Critical”. A table listing differences between these two new species and other similar species and an identification key are provided.


Introduction
Th e genus Myosotis L. is found in the Northern and Southern Hemisphere. Phylogenetic analyses of nuclear and chloroplast sequences suggest Myosotis originated in the Northern Hemisphere (Winkworth et al. 2002) and is nested within the tribe Cynoglosseae along with Trigonotis Steven (Weigend et al. 2010). In the Southern Hemisphere, New Zealand is the centre of diversity for the genus Myosotis, and 39 species have been listed for the country (Breitwieser et al. 2012). Th ese species occupy a great diversity of habitats ranging from coastal cliff faces and sand dunes to stream banks in forests, tussock grasslands, tarns, limestone and marble outcrops, and scree-slopes on the mountains of the Southern Alps. Th is ecological diversifi cation is matched by an equally remarkable diversifi cation of habit (cushion, single rosette, creeping/trailing stems), plant size (less than a centimetre to up to 40 cm height), and vegetative (leaf shape, indumentum type) and reproductive characters (white, yellow, brown-bronze, blue fl owers and automatic selfi ng and out-crossing species).
Despite the many phenotypic diff erences exhibited by New Zealand Myosotis, identifi cation at the species level can be challenging, especially when dealing with rare or under-collected species or poorly press-dried specimens in which fl ower and leaf characters have become distorted. Th e former situation, in particular, is commonly encountered by students of this genus, as many species have a highly restricted distribution with small-size populations (Brandon 2001). In fact, some of the currently recognised species are known only from a single locality (e.g. M. alboserica Hook.f., M. laeta Cheeseman) or, in more extreme cases, the type collection is the only collection ever made (e.g. M. laingii Cheeseman).
Currently, a revision of the genus Myosotis in New Zealand is underway and species limits for a number of widespread and critically endangered species are under assessment. Also, phylogenetic affi nities within New Zealand species are being studied using DNA sequences of both nuclear and chloroplast markers and AFLP fi ngerprinting data (Meudt et al. in preparation). Towards this end, a number of collecting trips to sub-alpine and alpine areas of the North and South Island of New Zealand have taken place between 2009 and 2012. An expedition to Kahurangi National Park in north-west Nelson (South Island, 41°11'26"S, 172°44'52"E), one of the diversity hotspots for Myosotis in the country, uncovered the existence of two morphologically and ecologically distinct entities, which are illustrated and described here as new species. An identifi cation key and a table summarising morphological diff erences between these two new species and other morphologically similar species are included.

Methods
Specimens were press-dried in the fi eld as soon as they were collected. Flowers, when available, were collected and preserved in 70% ethanol for later examination. Some samples were kept fresh and later photographed under a dissecting microscope. To test whether phenotypic diff erences observed in the fi eld were due to phenotypic plasticity, some samples were cultivated for two seasons, under common garden conditions. Vegetative and reproductive characters were observed and measured from fresh and press-dried material. Th ese records were later compared with descriptions in Moore (1961Moore ( , 1988, Moore and Simpson (1973) Moore (1961Moore ( , 1988, Moore and Simpson (1973) and representative voucher specimens (Appendix 1).  Fig. 1).
Distribution. Endemic to New Zealand, only found in north-west Nelson (South Island). Detailed geographic coordinates are not shown to protect this species from illegal collection but are available from the author on request.
Conservation status. Currently the existence of only fi ve populations of this species can be confi rmed. Two of them are within Kahurangi National Park where they occupy an approximate area of 6 m 2 and 1 m 2 . Th e number of individuals at each site is low, ca 20 and 3, respectively. Th ree other populations are found outside the park, two of them in smaller protected areas which are regularly monitored by the Department of Conservation. At all these sites the species occupies a similar habitat and a small area (Shannel Courtney, personal communication). Considering this information and following the New Zealand Th reat Classifi cation System (Townsend et al. 2008), M. chaff eyorum should be considered as "Nationally Critical".
Ecology. Th is is a perennial, self-pollinating species. It is habitat-specifi c and restricted to dry loose fi ne soil under shelters formed by limestone overhangs.
Discussion. Th e earliest known collection of M. chaff eyorum dates from 1967 (CHR 269160). Its distinctiveness from other species of Myosotis, however, was only noticed ca 10 years later when Anthony (Tony) Druce collected it while surveying the fl ora associated with Palaeogene calcareous rocks in north-west Nelson (Druce, unpublished). Druce noticed the overall similarity of this species to M. matthewsii and M. spathulata but also diff erences between them, which he wrote on the labels of the herbarium sheets of these collections (see Fig. 1). Th ese notes read "cf. M. matthewsii, but the fl owers are smaller" and "cf. M. spathulata, but stem not creeping".
Myosotis matthewsii and M. spathulata are the only forget-me-nots in New Zealand with orbicular rosette leaves with which M. chaff eyorum could be confused. Th e small fl ower with stamens within the corolla tube, the absence of roots at the nodes of the decumbent fl owering stem and the strigose indumentum of the leaf lamina, petiole and stems of M. chaff eyorum are key diagnostic characters to distinguish it from M. matthewsii or M. spathulata. In the absence of fl owers, M. matthewsii can be distinguished from M. chaff eyorum by the presence of arcuate and erect hairs on the upper surface of the rosette leaves, larger leaves and a longer pedicel at fruiting (see Table 1). As for M. spathulata, if no stems are present, it can be readily distinguished from M. chaff eyorum by the hispid indumentum on the leaf petiole and larger leaf lamina (see Table 1). Diagnosis. Similar to M. forsteri and M. brockiei, but diff ers from M. forsteri by its obovate rosette leaves; larger leaves at base of the cyme and smaller calyx at fruiting. It diff ers from M. brockiei by its smaller fl owers (3.8 -4.8 mm vs 9 -10 mm); stamens included within the corolla tube; fruiting calyx with shorter pedicel (2.5 -2.9 mm vs 3.6 -4.3 mm); and hispid indumentum on leaves and petiole.
Etymology. Th is species is named in honour of Lucy Beatrice Moore, New Zealand botanist (http://www.teara.govt.nz/en/biographies/5m55/1) who described several species of endemic Myosotis and revised this genus for the Flora of New Zealand (Allan 1961).
Distribution. Endemic to New Zealand. Known from a single location in Kahurangi National Park, north-west Nelson (South Island). Detailed geographic coordinates are not shown to protect this species from illegal collection but are available from the author on request. It is likely M. mooreana also occurs at two other sites within the Park (Shannel Courtney, personal communication) but this cannot be confi rmed at this stage.
Conservation status. Considering the small population size for this species (six individuals only), low number of mature individuals observed in the population and the small area of occupancy (less than 1m 2 ), and following the New Zealand Th reat Classifi cation System (Townsend et al. 2008), M. mooreana should be rated as "Nationally Critical".
Ecology. Th is is a perennial, fertile, self-pollinating species. It grows among the twigs and leaf-litter accumulated among large boulders under red beech (Nothofagus fusca) forest.
Discussion. Th ere are only two species of forget-me-nots in New Zealand that can be mistaken with M. mooreana; i.e. M. brockiei and M. forsteri. Th ese two are the only species growing in a similar habitat, under forest or scrub in north-west Nelson and throughout New Zealand, respectively. Th e main diff erences between M. mooreana and M. brockiei are the large fl owers with stamens fully exserted beyond the corolla tube in the latter species. Flowers in M. mooreana are only ca 5 mm across and stamens are always included within the corolla tube. In contrast, M. brockiei bears fl owers ca 1 cm across and anthers with long fi laments (ca 4 mm). When not fertile, indumentum and leaf shape are useful characters to distinguish between these two species. Myosotis mooreana bears oblanceolate rosette leaves and wide cauline leaves covered by a combination of arcuate, erect, antrorse and retrose hairs. Myosotis brockiei, in contrast, has narrowly elliptic leaves with a distinct tomentose almost greyish indumentum. Leaf shape is the most useful character to diff erentiate M. mooreana from M. forsteri. Th e latter species possess orbicular to broadly elliptic leaves with a well-defi ned petiole. Th e fl owers of both species are very similar in size (see Table 1) but the calyx of M. forsteri at fruiting is almost twice the size of the fruiting calyx of M. mooreana.