Dr Marianne le Roux

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SANBI section: 
Biosystematics Research and Biodiversity Collections
Position: 
e-Flora Co-ordinator
Address: 
Physical: Pretoria National Botanical Garden, 2 Cussonia Avenue, Brummeria, 0184, Pretoria, South Africa
Phone: 
+27(0)12 843 5124
Fax: 
+27(0)12 804 3211

Profile

Marianne le Roux completed her PhD in Botany in 2012 at the University of Johannesburg (UJ). In January 2012 she accepted a Postdoctoral Fellowship at UJ and was appointed as Research Associate in July 2012, where she taught both the third year undergraduate and Honours postgraduate courses in Plant Taxonomy for the Department of Botany and Plant Biotechnology (UJ). She served as secretary for the 6th International Legume Conference held in Johannesburg during January 2013. Marianne was appointed as the e-Flora Co-ordinator in March 2014, based at the National Herbarium in Pretoria.

Current activities

She is responsible for collecting and documenting information of all known plant species, ca. 21 000 taxa, in South Africa which will be published in an online Flora (the e-Flora of South Africa). This is in response to Target 1 of the Global Strategy for Plant Conservation which aims to compile a World Flora Online by 2020.

Her research interests include taxonomy related to the e-Flora of South Africa project as well as the taxonomy and systematics of Pelargonium (Geraniaceae) and the economically important family Fabaceae (legumes), particularly focused on the large cosmopolitan genus Crotalaria.

Selected publications: 
  • Oberholzeria (Fabaceae subfam. Faboideae), a New Monotypic Legume Genus from Namibia
    Oberholzeria etendekaensis, a succulent biennial or short-lived perennial shrublet is described as a new species, and a new monotypic genus. Discovered in 2012, it is a rare species known only from a single locality in the Kaokoveld Centre of Plant Endemism, northwestern Namibia. Phylogenetic analyses of molecular sequence data from the plastid matK gene resolves Oberholzeria as the sister group to the Genisteae clade while data from the nuclear rDNA ITS region showed that it is sister to a clade comprising both the Crotalarieae and Genisteae clades. Morphological characters diagnostic of the new genus include: 1) succulent stems with woody remains; 2) pinnately trifoliolate, fleshy leaves; 3) monadelphous stamens in a sheath that is fused above; 4) dimorphic anthers with five long, basifixed anthers alternating with five short, dorsifixed anthers, and 5) pendent, membranous, oneseeded, laterally flattened, slightly inflated but indehiscent fruits.
    Journal articles
    Swanepoel W., Le Roux M.M., Wojciechowski M.F., Van Wyk A.E.
    Published 2015 by Public Library of Science
    © Free of all copyright
    application/pdf icon application/pdf 1.5 MB
  • A new long-tubed subspecies of Pelargonium dipetalum (section Hoarea) (Geraniaceae) from the Albertinia-Swellendam area in Western Cape Province, South Africa
    Field studies confirmed that unusually long-tubed populations of Pelargonium dipetalum from between Swellendam and Albertinia, Western Cape Province, South Africa, are a distinct ecotype adapted to pollination by the long-proboscid fly, Prosoeca longipennis. The geographical and morphological isolation of these populations suggests that they are reproductively isolated from short-tubed populations, which are pollinated by bees. Objectives: To determine and describe the floral variation in P. dipetalum, with a view to recognising the long-tubed populations at some taxonomic level. Method: All available collections were measured and compared. Results: Populations of P. dipetalum were segregated into a short-tubed form with hypanthium 3 mm – 24 mm long and mostly pink petals that occurs from Betty’s Bay to Knysna, and a long-tubed form with the hypanthium 34 mm – 54 mm long and consistently white petals that is restricted to a small area east of Swellendam between Suurbraak and Albertinia. We described the long-tubed form as the new subspecies P. dipetalum subsp. stenosiphon. Conclusion: The new subspecies increases our understanding of the diversity in P. dipetalum and represents a new taxon of conservation concern.
    Journal articles
    Le Roux M.M., Manning J.C.
    Published 2014 by AOSIS OpenJournals
    © Le Roux M.M., Manning J.C.
    application/pdf icon application/pdf 10.32 MB
  • Creating an Online World Flora by 2020: a perspective from South Africa
    At the 10th Conference of the Parties of the Convention on Biodiversity (CBD), which was held in Nagoya, Japan, in October 2010, an updated Global Strategy for Plant Conservation (GSPC) was adopted as part of the plan of work of the CBD. Target 1 of the GSPC aims to produce an online Flora for all the plants of the world by 2020. Governments that have ratified the CBD will have to report over the next several years on progress towards achieving this challenging target. Floras are still widely regarded as a means of providing descriptive information and identification tools for the plants that occur in a specified region. Historically, Floras have included identification keys; scientific names with authorship for all taxa known to occur in the area; synonymy; descriptions; distributions within the region in question; specimen citations; habitat; literature references; and illustrations. Of these, nomenclature, descriptions, identification tools, illustrations and distributions are critical components. The approach being taken by South Africa, a biodiversity-rich country, in working towards achieving Target 1 of the GSPC by 2020 is presented and discussed, outlining a methodology that may be of practical use to other countries. We hope this will urge other countries to consider how they might meet this challenging conservation target.
    Journal articles
    Victor J.E., Smith G.F., Turland N.J., Le Roux M.M., Paton A., Figueiredo E., Crouch N.R., Van Wyk A.E., Filer D., Van Wyk E.
    Published 2014 by SpringerLink
    © SpringerLink
  • Phylogenetic Relationships of Tribe Crotalarieae (Fabaceae) Inferred from DNA Sequences and Morphology
    Tribe Crotalarieae is a large and diverse group of papilionoid legumes that largely occur in Africa. A systematic study of generic relationships within the tribe was undertaken using nucleotide sequences from the internal transcribed spacer (ITS) of nuclear ribosomal DNA, the plastid gene rbcL and morphological data. The Crotalarieae are supported strongly as monophyletic and sister to the tribe Genisteae. Lebeckia, Lotononis and Wiborgia are all paraphyletic in the molecular analyses and morphological data support the division of Lebeckia into three more natural genera (one of which includes the monotypic North African Spartidium). Four major lineages were identified within the tribe based on sequence data: the "Cape" group, comprising Aspalathus, Lebeckia, Rafnia, Spartidium and Wiborgia; the Lotononis group, comprising Lotononis pro parte, Pearsonia, Robynsiophyton, and Rothia; a group comprising Lotononis section Leptis, L. section Listia, and allies; and the Crotalaria group, comprising Bolusia, Crotalaria and Lotononis hirsuta (Lotononis section Euchlora). Morphological analysis yields a similar topology, except that Lotononis is monophyletic if L. hirsuta were excluded. When the molecular and morphological data sets are combined, the same major clades are retrieved as in the molecular analysis, with the notable exception that Lotononis and Lebeckia senso stricto are supported as monophyletic. The results from this study have important implications for the classification of the tribe Crotalarieae and present an important step towards a natural and phylogenetic generic classification for the tribe.
    (Source: Systematic Botany, 2008, 33 (4))
    Journal articles
    Boatwright J.S., Le Roux M.M., Wink M., Morozova T., Van Wyk B-E.
    Published 2008 by American Society of Plant Taxonomists
    © American Society of Plant Taxonomists
  • A taxonomic revision of Amphitrichae, a new section of Crotalaria (Fabaceae)
    Crotalaria sect. Amphitrichae is described as new to give formal recognition to a strongly supported clade revealed by a recent molecular systematic study. The five known species are restricted to the arid western parts of southern Africa (C. colorata, C. excisa, C. humilis, C. meyeriana, and C. pearsonii). Species of the section are morphologically distinct in having (1) hairs distributed all around the distal part of thestyle; (2) ridge callosities on the standard petal blade and claw; (3) a rounded keel; (4) a twisted keel beak; and (5) a rounded style. A cladistic analysis of 18 morphological characters resulted in a well-resolved cladogram that recovers relationships within the section. The study revealed that two new species should be recognised, described here as C. giessii and C. kolbergii. A taxonomic revision of the section ispresented, with descriptions, diagnostic characters, distribution maps, and illustrations of all seven recognised species.
    Journal articles
    Le Roux M.M., Van Wyk, B-E.
    Published 2015 by American Society of Plant Taxonomists
    © American Society of Plant Taxonomists
  • A global infrageneric classification system for the genus Crotalaria (Leguminosae) based on molecular and morphological evidence
    Crotalaria is a large genus of 702 species with its centre of diversity in tropical Africa and Madagascar and secondary radiations in other parts of the world. The current infrageneric classification system is based on morphological and morphometric studies of the African taxa only and is here re-evaluated using a phylogenetic approach. DNA sequences derived from the nuclear ITS and the plastid matK, psbA-trnH and rbcLa markers were analyzed using parsimony and model-based (Bayesian) approaches. The resultant molecular phylogeny allowed for a new interpretation of diagnostically important morphological characters, including specialisations of the calyx, keel, standard petal and style, which are variously convergent in several unrelated infrageneric groups. Of particular interest is the congruence between the new phylogeny and the distribution of standard petal callosity types. A sectional classification system for the entire genus is proposed for the first time. The new system that is formalised here comprises eleven sections: Amphitrichae, Calycinae, Crotalaria, Geniculatae, Glaucae, Grandiflorae, Hedriocarpae, Incanae, Schizostigma, Borealigeniculatae and Stipulosae. Sectional limits of the Geniculatae, Calycinae and Crotalaria are modified. The subsections Stipulosae, Glaucaeand Incanae are raised to sectional level, while some groups previously recognized as subsections are abandoned due to non-monophyly (subsections Chrysocalycinae, Hedriocarpae, Macrostachyae and Tetralobocalyx). Two new sections are recognized, Amphitrichae and Borealigeniculatae.
    Journal articles
    Le Roux M.M., Boatwright J.S., Van Wyk B-E.
    Published 2013 by International Association for Plant Taxonomy
    © International Association for Plant Taxonomy
  • The systematic value of flower structure in Crotalaria and related genera of the tribe Crotalarieae (Fabaceae)
    Flowers in the tribe Crotalarieae of the family Fabaceae are generally adapted to bee pollination mechanisms. Molecular systematics have recently provided a major step towards a profound insight into generic relationships, thereby creating the opportunity to re-evaluate the taxonomic and functional significance of flower structure in the tribe, with emphasis on the large genus Crotalaria. A representative sample of flowers from 211 species was dissected to record morphological character states. These data were supplemented from the literature to allow for generalizations for the tribe as a whole. Six structural–functional flower types were identified: (1) pump; (2) gullet; (3) hugging; (4) saddle; (5) tunnel and (6) brush (saddle and tunnel types described here for the first time). Crotalaria uniquely has the brush type, characterized by a rostrate keel, highly dimorphic anthers, stylar trichomes and elaborate callosities on the standard petal. Remarkably, Crotalaria and Bolusia are the only genera of the tribe Crotalarieae with callosities present in all of the species. In other genera, callosities are generally absent or infrequent. Trends towards specialization of pollination syndromes are apparent as assemblages of apomorphic states that co-occur in what we refer to here as “specialized flowers”; individual characters are labile or non-homologous (e.g. callosities) and diagnostically less valuable. Unique combinations of flower characters are often useful to support current generic concepts in Crotalarieae.
    (Source: Flora, 2012, 207(6))
    Journal articles
    Le Roux M.M., Van Wyk B-E.
    Published 2012 by Elsevier
    © Elsevier GmbH
  • The systematic significance of morphological and anatomical variation in fruits of Crotalaria and related genera of tribe Crotalarieae (Fabaceae)
    The phylogenetic and taxonomic significance of morphological and anatomical trends in fruits of tribe Crotalarieae has been evaluated, with emphasis on the genus Crotalaria and its seemingly distinctive, inflated and balloon-shaped pods. In addition to the normal explosive dehiscence as a means of dispersal, several genera (including Crotalaria) show independent evolution of modifications apparently adapted for dispersal by wind, water and gravity. Transverse sections were made of mature pods of 142 species from the 12 currently recognized genera of Crotalarieae. The taxa differ in the orientation of the fibres (related to dehiscence or non-dehiscence), the overall thickness of the fruit wall, the relative proportions of the pericarp layers, the degree of lignification and the presence or absence of trichomes. Three basic pericarp types can be distinguished: type I, with one, two or three zones of various numbers of cell layers of fibres (almost all genera); type II, with a single cell layer of fibres (only in Rothia, Robynsiophyton, Lebeckia and Lotononis sections Listia and Leobordea); and type III, with one zone of several cell layers of gelatinous fibres and multicellular trichomes associated with the endocarp (only in some species of Calobota and Wiborgiella). Considerable variation was encountered in the tribe, but Crotalaria appears to be rather uniform, with type I predominating.
    (Source: Botanical Journal of the Linnean Society, 2011, 165(1))
    Journal articles
    Le Roux M.M., Van Wyk B-E., Boatwright J.S., Tilney P.M.
    Published 2011 by John Wiley & Sons, Inc.
    © The Linnean Society of London
  • A revision of Lebeckia sect. Lebeckia: The L. pauciflora and L. wrightii groups (Fabaceae, Crotalarieae)
    All 14 species of the type section of the genus Lebeckia Thunb. are endemic to the Cape Floristic Region and are easily recognized by their phyllodinous, acicular (needle-shaped) leaves. Ten of the 14 species, comprising the L. sepiaria and L. plukenetiana groups, have already been revised. The last two groups are formally treated in this paper: 1. the L. pauciflora group (two virgate perennials with terete to semi-terete, stipitate fruits) and 2. the L. wrightii group (two trailing fireweeds with flat, sessile fruits). One of these, L. uniflora B-E.van Wyk and M.M.le Roux sp. nov., is here described as new. The new species was previously confused with L. wrightii (Harv.) Bolus but differs in the single-flowered inflorescences, larger flowers and black seeds. The nomenclature, typification, morphological and diagnostic characters are presented as well as distribution maps. A comprehensive key to all 14 species of section Lebeckia is provided.
    (Source: South African Journal of Botany, 2009, 75(1) )
    Journal articles
    Le Roux M.M., Van Wyk B-E.
    Published 2009 by Elsevier
    © SAAB
  • A revision of Lebeckia sect. Lebeckia: The L. plukenetiana group (Fabaceae, Crotalarieae)
    Lebeckia Thunb. section Lebeckia includes 14 species, all with phyllodinous, acicular leaves, that are endemic to the Cape Floristic Region. As part of a taxonomic study of the genus Lebeckia, the L. plukenetiana group of section Lebeckia has been revised. The species of this group have stipitate, flat fruit and a prostrate habit. A study of vegetative and reproductive morphology showed that six species can be recognised, two of which are here described as new: 1. L. brevipes M.M. le Roux and B.-E. Van Wyk sp. nov. (previously misidentified as L. longipes Bolus and L. pauciflora Eckl. and Zeyh.) which is easily recognised by the short stipe, elliptic, flat fruit, wing petals that are as long as the keel petal and an orbicular standard petal; 2. L. zeyheri M.M. le Roux and B.-E. Van Wyk sp. nov. (previously known as L. plukenetiana E. Mey. var. brachycarpa Harv.) which has subsessile, short fruit, wing petals that are as long as the keel petal and an orbicular standard petal. The correct nomenclature and typification of the species are presented, together with descriptions, diagnostic characters and distribution maps.
    (Source: South African Journal of Botany, 2008, 74(4))
    Journal articles
    Le Roux M.M., Van Wyk B-E.
    Published 2008 by Elsevier
    © SAAB
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