Browsing by Author "Linder, H P"

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    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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    Flora of the Cape Peninsula : endemism, threatened plants and conservation in perspective
    (1995) Trinder-Smith, Terry H; Linder, H P
    An updated and nomenclaturally accurate species list of flora of the Cape Peninsula was established. distribution of each of species was then databased from c. 42 000 herbarium sheets housed in the three main herbaria in South Africa. The composition of flora, taxonomic and biological aspects of endemic and threatened taxa and the conservation status the flora and endemic fauna of the Cape Peninsula were then investigated. A large nomenclatural and taxonomic change was detected with % of having undergone name changes since the last taxonomic survey in 1950. There are more families and genera than previously recorded as a result of many taxonomic revisions. Monocotyledons, though only representing 18% of families, are well represented at the generic %) and specific (29.4%) level with both petaloid and non-petaloid monocotyledons being important. Pteridophytes in contrast represent 10.9 % of families and only of species. Of the 2285 in the flora 90 are endemics and 141 are threatened. The Bykov's level of endemism at 1 for the Peninsula was high in global terms. Endemic and threatened taxa were found not to be a random assemblage taxonomically, with and Proteaceae overrepresented in terms of endemics. The aforementioned families Restionaceae and Orchidaceae were over-represented with respect to threatened taxa. A logistic regression analysis on the biological traits of endemic taxa showed the most likely biological profile of a Peninsula endemic to be a low, non-sprouting shrub with short-distance dispersal mechanisms. The profile of threatened taxa was found to be similar to endemic taxa. Many of these biological characteristics make these taxa vulnerable to extinction and therefore have certain management implications concerning their sustained existence. Furthermore, Peninsula endemics and threatened plants were found to be significantly over-represented in mid- to high altitude, mesic to wet habitats. However, urbanization has reduced certain lowland vegetation types thus causing over-representation of these taxa in these areas. These habitats require urgent protection. An analysis using a Geographic Information System (GIS) showed the present reserve system inadequate in terms of protecting all plant and endemic faunal species on the Peninsula. The inclusion of all publicly owned land into the reserve system improved the conservation status dramatically, with only 13 species remaining unconserved. A third scenario is assessed whereby it is assumed that no public land is available for inclusion into a reserve system. An iterative reserve selection algorithm was then applied to allocate areas outside existing reserves to ensure each species is protected at least once. A total of 51 cells were required. All cells but for one lay in close proximity to existing reserves and could be incorporated at relatively little expense. Finally, based on a minimum cost consideration, it was suggested that all publicly owned land become incorporated into a reserve system and private reserves be created to protect the few unprotected species. It was also stressed that the current management system was inadequate and a new, single, scientifically based management plan needs to be implemented.
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    Phylogeny and character evolution in the Lampranthus-group (Aizoaceae-Ruschioideae)
    (2001) Klak, Cornelia; Hedderson, Terry A; Linder, H P
    The phylogenetic position of the Lampranthus - group (Ruschioideae, Aizoaceae), with particular emphasis on the large genus Lampranthus, was studied using morphological characters and DNA sequence from the trnL - trnF region of the chloroplast genome, the nuclear ribsomal internal transcribed space (ITS) region and the 5S non-transcribed spacer. The phylogenies 59 species in the 29 genera of succulent Aizoaceae, including two species from subfamily Mesembryanthemoideae, are presented.
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    Systematic studies in the genus Melianthus L. (Melianthaceae)
    (1999) Dlamini, Titus; Linder, H P
    The taxonomy and biology of Melianthus is reviewed. The taxonomic ranks of the two subspecies, M. dregeanus ssp. insignis and M. pectinatus ssp. gariepinus, are considered. A phenetic analysis indicates that M. insignis is similar to M. dregeanus but distinct enough to be recognised as a separate species. Though M. pectinatus ssp. gariepinus has not been investigated in detail, the implication of the resolved phylogeny on its status is discussed. The phylogeny of Melianthus and related taxa is reconstructed using cladistic analysis of morphological characters including vegetative morphology, pollen structure, seed-coat structure and the extremely diverse floral morphology. Bersama and Greyia, the probably sister species are used as outgroups for the analysis. The monophyly of MeIianthus is demonstrated, M. major is retrieved as the basal taxon for the study group and the rest of the species are scattered between two major clades. Species distributions are mapped and the pattern indicates that Melianthus has adapted to the Afromontane grasslands in the east of southern Africa as well as the semi-arid parts in the west. In terms of this distribution and the presumed phylogeny, the extent to which the situation in Melianthus supports existing ideas on the evolution of the southern African flora is explored. Ecological preferences for the species are described, then the extent to which they might have driven speciation in the genus is investigated. Evidence from floral ontogeny, indicating that the developmental pathways in Melianthus flowers vary quantitatively, hence the diversity, is also presented. Modifications of the basic Melianthus flower, which may have led to the complex structure in the genus, are considered and floral adaptations to pollinators are investigated. The role of pollinators in the evolution of floral diversity in Melianthus is also investigated. Finally, a key and full descriptions of all the species are provided.
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    Systematics of psilocaulon N.E.BR. (Aizoaceae)
    (1997) Klak, Cornelia; Linder, H P
    On the basis of herbarium, living and pickled material the morphology and systematics of Psilocaulon N. E. Brown sensu Ihlenfeldt & Bittrich is investigated. Thirteen species (including one insufficiently known species) are recognized: P. articulatum, P. bicorne, P. coriarium, P. dimorphum, P. dinteri, P. foliosum, P. gessertianum, P. granulicaule, P. junceum, P. leptarthron, P. parviflorum, P. salicornioides, P. subnodosum. Species of Mesembryanthemum, Prenia, Brownanthus, Aspazom and Aptenia are used as outgroups in a cladistic analysis of Psilocaulon. The monophyly of Psilocaulon is demonstrated. As a result P. rapaceum Jacq. is excluded and transferred to Caulipsolon Klak gen. nov. The position of Psilocaulon and the monotypic genus Caulipsolon within the subfamily Mesembryanthemoideae is discussed. However, relationships of Psilocaulon and Caulipsolon to other genera remain obscure, since no synapomorphies were found to indicate sister relationships. More sampling among outgroups and/or a future molecular study may help to elucidate relationships among the genera of the Mesembryanthemoideae. Geographical distribution patterns for all species and the number of species per half-degree grid square are given. It is discussed how species diversity and geographical distribution in Psilocaulon contrasts with or corroborates existing ideas of centres of diversity and distribution patterns in the Mesembryanthema. Each species is described in detail. A description of the genera Psilocaulon and Caulipsolon is given and a key to the species is provided. Material examined is cited and full synonomy is given.
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    The taxonomy of the subtribe aveninae excluding helictotrichon schult Part 1 & 2
    (1991) Sokutu, Tamsanqa Mthunzi; Linder, H P
    The sub-tribe Aveninae Presl in southern Africa is represented.by nine genera, eight of which are included in this study. Most of these genera have been introduced from elsewhere, in most cases from Europe. A morphological and anatomical account of this subtribe excluding Helictotrichon Schult. is given and keys to genera and species are also provided. Characters that are employed in Flora guropaea to differentiate between genera and species have, with few exceptions been fotinci to be useful.