Browsing by Author "Muasya, A M"

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    Aspalathus abbottii (Fabaceae: Crotalarieae) a new species from KwaZulu-Natal South Africa
    (2011) Stirton, C H; Muasya, A M
    A new species Aspalathus abbottii C.H. Stirt. & Muasya, is described. The species is known only from Oribi Flats, KwaZulu-Natal, where it grows in grassland vegetation. The new species is characterised by its rigid spreading habit, densely and shortly villous branches, glabrous bracts and bracteoles, and 1(2) bright yellow flowers borne on short lateral shoots. It is most similar to other grassland species, A. frankenioides DC. and A. gerrardii H. Bol., all from the summer rainfall area of South Africa but differs in its rigid spreading habit, few bright yellow flowers per flowering branchlet, glabrous bracts and bracteoles, villous yellowish-green seasonal shoots, and its pale brown to tan over-seasonal branches with a blackish lattice of peeled bark.
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    Open Access
    Biology and resource acquisition of mistletoes, and the defense responses of host plants
    (2022-02-21) Muche, Meseret; Muasya, A M; Tsegay, Berhanu A
    Background Mistletoes are the most successful group of obligatory hemi-parasitic flowering plants that attach to the host via haustorium for obtaining water and minerals. This review aims to assess the current knowledge on mistletoes host plant recognition, haustorium formation, water/minerals acquisition, and host plants’ defense signaling and responses against mistletoe attack. Results Some mistletoes are host-specific while others are generalists occurring on a wide range of vascular plants. The host nitrogen (N) content, parasite–host chemical interactions, compatibility, and dispersal agents are the main determinant factors for host specificity. Mistletoes take up substantial amounts of water and minerals passively via apoplastic routes, and most are xylem feeders, but could shift to phloem-feeding during the physiological stress of the host plants. Current evidence highlighted that cell wall loosening and modification are critical during the development of the haustorium in the host tissue. This is made possible by the application of physical pressures by the developing haustorium and cell wall degradation using enzymes (xyloglucan endotransglycosylases, glucanase, expansins, etc.) produced by the mistletoe. Host plants defend against mistletoe infection mechanically by producing spines, lignin, suberin, etc., which discourages dispersers, and chemically defend by killing the infector or inhibiting the establishment of the haustorium using their secondary metabolites such as terpenes, phenolics, and N-containing compounds. Although the host plants' response to mistletoe attack resembles the response to other biotic stresses, unlike short-term stressors, the effect of mistletoe attack is long-term and depends on the parasite load. Infection by mistletoe leads to water and nutrient stress of the host plant and deteriorates its healthy establishment and survival. Conclusion Mistletoes are heterogeneous group in the order Santalales which have versatile mechanisms for pollination, seed dispersal and nutrient acquisition from host plants. Infection by mistletoes triggers host plant responses, varying from mechanical to chemical mechanisms which are analogous to herbivory defences, and negatively impacts host plant growth and reproduction.
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    Open Access
    Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora
    (BioMed Central, 2011-02-08) Warren, Ben H; Bakker, Freek T; Bellstedt, Dirk U; Bytebier, Benny; Claßen-Bockhoff, Regine; Dreyer, Léanne L; Edwards, Dawn; Forest, Félix; Galley, Chloé; Hardy, Christopher R; Linder, H P; Muasya, A M; Mummenhoff, Klaus; Oberlander, Kenneth C; Quint, Marcus; Richardson, James E; Savolainen, Vincent; Schrire, Brian D; van der Niet, Timotheüs; Verboom, G A; Yesson, Christopher; Hawkins, Julie A
    Background: The best documented survival responses of organisms to past climate change on short (glacialinterglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa’s biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results: Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions: Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora’s extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record.
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    Isolepis namaquana (Cypereae, Cyperaceae), a new endemic species from the winter rainfall area of South Africa
    (Elsevier, 2011) Muasya, A M; Viljoen, J; Stirton, C H
    A new species, Isolepis namaquana Muasya & J.Viljoen, is described and illustrated. It is known from two localities in Namaqualand: near Kamieskroon and at the foot of the Matsikammaberge, where it grows in ephemeral wetlands. The tufted annual species is diagnosed by floral and fruit characters including glume size, bifid stigma and colliculate nutlet surface ornamentation.