Browsing by Subject "Plant Systematics"

Now showing 1 - 5 of 5
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    Contributions to the systematics of the genus Schizochilus
    (1971) MacRobert, M; MacRobert, M; E.A.C.L.E Schelpe.; Schelpe, E A C L E
    The genus Schizochilus, first described by Sonder in 1847 as an extra-tropical Southern African orchid, is based upon material collected by Ecklon and Zeyher in moist places in the Winterberg mountains. The main characters of the flower are a spurred, fleshy three-cleft lip; and free, erect sepals and petals, all three sepals being equal and the petals much smaller than the sepals. The type species, S. zeyheri Sond., is described as having a small number (2-3) of linear-oblong basal leaves and a spike of 16-20 small flowers. Sepals and petals are both noted as white, the sepals about 0,5 cm in length (2.5 lines) and marked with 3 rosy veins, the petals lanceolate and half the length of the sepals. The spur is "not much shorter than the labellum" and the ovary, "almost twice the length of the spur". The lip itself, obovate in outline, is covered with very small crystalline papillae, the lateral lobes being "somewhat shorter than title broader, obtuse intermediate lobe". There appears to be no mention of the basal tubercles or calli on the lip.
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    The evolution of the Afrotemperate-endemic genus Macowania (Asteraceae) in the Drakensberg region of South Africa
    (2010) Bentley, Joanne; Verboom, George Anthony; Bergh, Nicola G
    The cosmopolitan Asteraceae tribe Gnaphalieae, or paper daisies or everlastings, form a significant component of both the dry and cool temperate floras of southern Africa. Within this tribe exists a small Afrotemperate genus, Macowania, endemic to the grassland biome of South Africa and occurring almost exclusively within the Drakensberg region, apart from two disjunct species in North Africa. The age, relationships and geographic origin of Macowania is investigated in order to provide insight into the factors affecting speciation, especially uplift events, on this small Afrotemperate genus. A well-supported phylogenetic hypothesis based on both nuclear and chloroplast genes suggests that Macowania is sister to a clade corresponding to the Relhania clade s.s., and that these are in turn sister to a clade containing the genera Athrixia and Pentatrichia. Macowania is monophyletic only with the inclusion of the enigmatic monotypic genus Arrowsmithia, resulting in the future synonymy of Macowania with Arrowsmithia. The anomalous species M. pinifolia, previously part of the genus Athrixia, is placed in a polytomy with the Relhania s.s. clade and the remaining species of Macowania and Arrowsmithia. DNA sequence data could not be obtained for several Macowania species, including the taxa from North Africa. The placement of these species within Macowania is confirmed by means of a parsimony analysis of morphological characters against a molecular backbone constraint tree. One species, M. tenuifolia, is well-supported in two different placements within Macowania by chloroplast and nuclear DNA sequence data. The best position of this species is inferred by incongruence decomposition analysis and morphological affinities. Bayesian relaxed clock methods and ancestral area reconstruction using maximum likelihood and squared change parsimony estimate the age and ancestral area of the genus, and determine the timing and route of colonisation of the Drakensberg. Diversification within Macowania is consistent in timing with the uplift events during the Miocene and Pliocene that resulted in significant vertical movement in eastern South Africa, suggesting that colonisation of the high-elevation Drakensberg grassland by Macowania was promoted by uplift. The topographic heterogeneity and increased river action resulting from the uplift may also have promoted evolution into new habitats and potentially mediated the movement of the ancestor of Macowania into the Drakensberg region via riparian habitats.
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    Morphological study of Schizaea Pectinata (L.) Sw. (Schizaeaceae)
    (2000) Mwafongo, Elizabeth; Roux, J P
    Morphometrics was used to study variation in Schizeae pectinata as previous study showed that material originating from the summer rainfall area of South Africa differ in several aspects from that originating from the winter rainfall area. The plant has a simple structure and consequently spore, stoma and sporangia sizes, as well as the number per lamina was studied to determine if the species can be subdivided into two groups, e summer and e winter rainfall group, as was previously hypothesised. Univariate and bivariate methods were used to display the extent of variation within the species. Univariate analysis reflect variability of spore and stomata size, and the number of pinna pairs per lamina. Statistical analyses showed that interpopulation variation for these characters are often highly significant. Phonetic methods were used in the analyses of the data set and shows continuous variation in this species. This continuous variation in Schizaea pectinata could be linked to a phenotypic response to environmental differences between the two regions.
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    Phylogeography and population genetics of two forest endemic mosses in the Cape Floristic Region
    (2002) McGrath, Kate; Hedderson, Terry A
    Different histories for forests in Southern Africa have been hypothesized from vegetation biogeography and pollen analysis. However, the history of forests is still controversial. Phylogeography uses gene genealogies to infer history of distributions. Two forest endemic moss species were sampled: Leptodon smithii; and Neckera valentiniana. Two gene regions were used, trnLF (chloroplast genome) and ITS1 (nuclear genome). Neckera valentiniana showed no variation from the populations sampled. Results from Leptodon smithii based on the trn and ITS region suggest that forests once were widespread, but then became fragmented. Dispersal corridors still exist between Southern Cape populations and Western Cape populations.
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    The structure of the perennial growth of Disa uniflora Berg. (Orchidaceae)
    (1990) Thomas, Janet Clare; Linder, H Peter
    The perennation of orchids is poorly understood, in particular that of the Orchidoidae. The understanding of perennation in the Orchidoidae is important because the root-stem tuberoid is used as the one character defining the Orchidoidae as a monophyletic group. The root-stem tuberoid has never been examined for variation before. This project focuses on perennial growth in the Diseae in order to study the structure and function of the root stem tuberoid in relation to other organs and to contribute to the understanding of Orchidoid phylogeny.