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    Taxonomic revision of the southern hemisphere pygmy forget-me-not group (Myosotis; Boraginaceae) based on morphological, population genetic and climate-edaphic niche modelling data
    (CSIRO Publishing, 2022-05-05) Prebble JM; Symonds VV; Tate JA; Meudt HM; Wilson P
    A taxonomic revision of the southern hemisphere pygmy forget-me-not group (Myosotis L.; Boraginaceae) is presented here. Climate-edaphic niches are modelled and compared for five species in the pygmy group, namely, M. antarctica Hook.f., M. brevis de Lange & Barkla, M. drucei (L.B.Moore) de Lange & Barkla, M. pygmaea Colenso and M. glauca (G.Simpson & J.S.Thomson) de Lange & Barkla, and one unnamed putative taxon, M. "Volcanic Plateau". In this case, niche-modelling data mostly do not aid species delimitation, but morphological and genetic data provide evidence for recognising the following three species within the group: M. brevis and M. glauca (both endemic to New Zealand), and an enlarged M. antarctica (native to New Zealand, Campbell Island and Chile). Myosotis antarctica is here circumscribed to include M. antarctica sens. strict., M. drucei and M. pygmaea. The following two allopatric subspecies of M. antarctica are recognised on the basis of minor morphological differences: subsp. antarctica (formerly M. antarctica from Campbell Island and Chile, M. drucei and M. "Volcanic Plateau") and subsp. traillii Kirk (formerly known by New Zealand botanists as M. pygmaea Colenso, an illegitimate name). For all three species, which are considered Threatened or At Risk, most of their genetic variation is partitioned between rather than within populations, meaning that conserving as many populations as possible should be the priority to minimise risk of extinction.
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    Species delimitation and the population genetics of rare plants : a case study using the New Zealand native pygmy forget-me-not group (Myosotis; Boraginaceae) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Manawatū, New Zealand
    (Massey University, 2016) Prebble, Jessica Mary
    Myosotis L., the forget-me-nots, is a genus of about 100 species distributed in the Northern and Southern Hemispheres. There are two centres of diversity, Eurasia and New Zealand. The New Zealand species are a priority for taxonomic revision, as they comprise many threatened species and taxonomically indeterminate entities. This thesis includes a taxonomic revision of the native New Zealand Myosotis pygmaea subgroup, followed by an exploration of the genetic effects of rarity, and implications for conservation management. Species delimitation follows the general lineage model, in which multiple lines of evidence are analysed to identify evolutionary lineages. The morphological data collected from herbarium specimens and live plants grown in a common garden were used to delineate the M. pygmaea group and identify several groups within it that nearly matched the current taxonomy. High levels of plasticity were also uncovered. Microsatellite loci were developed as polymorphic markers for the M. pygmaea group for species delimitation and conservation genetics. Over 500 individuals were genotyped, mostly focusing on the M. pygmaea group but including several outgroup species for comparison. Several genetic clusters were identified showing morphological or geographic patterns. Considering both the genetic and morphological data, as well as novel ecological niche modelling, there is evidence for three main lineages within the M. pygmaea group which are formally recognised as M. antarctica, M. brevis and M. glauca. M. antarctica is further subdivided into two subspecies based on allopatry and morphology, namely subsp. antarctica and subsp. traillii (formerly M. drucei + M. antarctica and M. pygmaea, respectively). Using this new taxonomic framework to explore genetic variation relative to rarity shows very little difference among species. This is most likely due to the confounding effect of high levels of self-fertilization and low dispersal, which means that the majority of genetic variation within these species is partitioned between, rather than within populations. The implication for conservation is that each population is equally important in terms of their contribution to the genetic diversity of each species. This thesis represents a major increase in our knowledge of the evolution, systematics, taxonomy, rarity and conservation of New Zealand native forget-me-nots.
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    Evolution of the New Zealand alpine flora : origins, diversification and dispersal : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Plant Biology and Biotechnology at Massey University, Palmerston North, New Zealand
    (Massey University, 2000) Winkworth, Richard Charles
    This thesis describes molecular systematic studies that test hypotheses concerning the age and origins of the New Zealand alpine flora. Analyses of nuclear and chloroplast DNA markers for two plant groups that have radiated extensively in the alpine zone of New Zealand - the genus Myosotis (Boraginaceae) and the Australasian apioid Umbelliferae - are reported. The molecular results suggest that the diversification of these groups in New Zealand has occurred since the late Tertiary. This finding corroborates recent molecular systematic studies on other New Zealand plant groups. Taken together, these studies suggest that New Zealand's modern floristic diversity was greatly influenced by dramatic global climate change during the late Tertiary and Quaternary. These results are also consistent with those reported for plant groups overseas. In these, recent diversification has occurred with Quaternary climatic fluctuations (Comes & Kadereit, 1998) and colonisation of insular environments (Crawford & Stuessy, 1997) The molecular analyses also suggest that since the late Tertiary, Myosotis and the Australasian Apioideae have been involved in transoceanic dispersal events both to and from New Zealand. However, while most other molecular studies have provided evidence for the importance of circum-polar westerly winds, the present data suggests that, for Myosotis and with less confidence the apioid genera, some dispersal events have been in a westerly direction. Since this finding was made, late Tertiary and Quaternary westward dispersal has also been inferred for other New Zealand alpine plants. These observations suggest that passive eastward wind dispersal can not explain the distributions of all southern Pacific plant groups. The present study, as well as other recent studies, has highlighted the need to develop molecular tools and analytical approaches for describing the potentially complex evolutionary relationships between taxa that have originated since the late Tertiary. Here, the amplified fragment length polymorphism (AFLP) method was investigated as a means of identifying fast evolving genome regions in New Zealand Myosotis. Preliminary analyses suggest that this is a useful approach for locating highly variable molecular markers. However, like other rapidly evolving regions (e.g. Buckler et al., 1997) some of the derived markers were multiple copy and polymorphic at different loci within a single genome. This feature of fast evolving genome regions is problematical since bifurcating evolutionary analysis models will poorly represent such complex data. For this reason split-decomposition was investigated as an alternative method for data representation. This approach was found to have both advantages and limitations for studying late Tertiary or Quaternary radiations.