Browsing by Subject "Succulent Karoo"

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    Assessing Intra-seasonal land surface change and long term trends in the Succulent Karoo biome using coarse resolution satellite data and interpolated rainfall surfaces
    (2005) Roberts, Jonathan Wesley; Hewitson, Bruce
    The Succulent Karoo is a biodiversity hot spot situated along the west coast of southern Africa. While it is predominantly recognized as a west coast vegetation type its borders stretch as far east as Steytlerville in the Little Karoo. The area contains the largest number of endemic succulent species in the world and harbors nearly 10 percent of the total number of succulent species worldwide. Furthermore, spring mass-flowering events draw thousands of tourists to the region, providing welcome input to the local economies. The floral diversity is however under threat from various environmental forces. These forces include inappropriate land use practices resulting in Land Degradation and the ever-present threat of Climate Change. With the pressures that are presently being placed on the biome and the threat of future changes to the climatic regime, it is necessary to develop methodologies to monitor vegetation changes within the biome. These methodologies should be able to discern between climate driven and land use driven changes that may denude the rich biological diversity of the biome. Monitoring regional changes in vegetation necessitates the use of coarse resolution satellite data in conjunction with statistically derived rainfall surfaces. For the purposes of this study intraseasonal land surface change is monitored using the Normalized Difference Vegetation Index derived from the National Oceanic and Atmospheric Administration (NOAA), Advanced Very High Resolution Radiometer (AVHRR). Rainfall surfaces are taken from Hewitson and Crane (2005). Ancillary temperature data taken from NCEP reanalysis is also used. Three analysis methodologies are used to answer questions relating to the relationship between rainfall and vegetation growth. Firstly, a Spatio Temporal Correlation filter (STCf) is used to investigate the spatial and temporal nature of seasonal vegetation changes (Where is seasonal vegetation change homogenous?). Secondly Principal Component Analysis is used to monitor seasonal vegetation change (What is the seasonal nature of NOVI in the Succulent Karoo?) and finally the relationship between precipitation and vegetation growth is classified using a Self Organising Map ( When and where is the relationship between rainfall and vegetation growth strongest?). Results from the three analysis methodologies are combined to determine zones of potential critical change. Within each of these zones drivers of vegetation change are identified and discussed. Most notably, regression analysis conducted on the output of the Self Organising Map indicates that temperature plays a more important role in vegetation growth than precipitation. This result indicates that the biome may be more vulnerable to the impacts of Global Warming than previously anticipated. Results also indicate that future studies of vegetation change using satellite imagery should be cognisant of the potential effects of soil background reflectance. In conclusion this thesis shows that much of the Succulent Karoo biome is under threat from both inappropriate land use and Climate Change, which may potentially lead to degradation of the biodiversity and rangelands that support the local population.
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    Open Access
    Distribution and phylogenetic inference within the flightless spring katydids (Tettigoniidae: Brinckiella Chopard, 1955) in the Greater Cape Floristic Region
    (2022) Guta, Ricardo José; Janion-Scheepers, Charlene; Naskrecki, Piotr
    The genus Brinckiella is an endemic group from the Greater Cape Floristic region (GCFR) with several undescribed species. Some of them are of conservation concern, categorized by IUCN as Endangered (EN) and Vulnerable (VU) due to their restricted distribution caused by livestock overgrazing, agriculture, and urbanization. However, data are still missing to fully assess their distribution pattern and conservation status. Moreover, although the phylogeny of katydids was recently inferred, Brinckiella was not included in that analysis. Thus, its closest relatives and evolutionary history are still unknown. This study aimed to investigate the distribution and phylogenetic inference within the genus Brinckiella, map the distribution of its species, delimit the species through taxonomy and genetics, and elucidate the phylogenetic relationship and divergence time within the genus. Specimens were collected by hand and sweep netting. Phylogenetic inference was done using the COI gene and analysed under Maximum likelihood and Bayesian inference. This study identified 13 morphospecies of Brinckiella, of which five are new, undescribed species. The genus is currently distributed in 27 vegetation types in three biomes, and apart from the Fynbos and Succulent Karoo biomes, the genus also occurs in the Azonal vegetation biome. Fynbos had the highest number of species of Brinckiella, which is likely related to the vast diversity of plant that they are associated with and probably feed on. In the Succulent Karoo the distribution of Brinckiella might be associated with seasonal plants that occur in the spring and at the beginning of summer. The genus may be monophyletic, and it split from the common ancestor shared with Holochlora fruhstorferi Carl, 1914 about 14.2 Mya, and it split again from the common ancestor shared with Isophya major Brunner von Wattenwyl, 1878, Phaneroptera gracilis Burmeister, 1838 and Kuwayamaea chinensis (Brunner von Wattenwyl, 1878) at 10.16 Mya and diverged in the late Miocene around 8.79 Mya, producing two main clades (A and B). Clade A diverged 7.85 Mya and is composed by two closely related species: B. aptera and B. mauerbergerorum, while Clade B diverged 7.24 Mya and gave rise to two lineages (L1 and L2). Brinckiella wilsoni constitutes L1, and L2 split later in the early Pliocene around 4.74 Mya, and is represented by two sister species, B. arboricola and B. sp. n. 5.
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    Notes on the genus Trachyandra (Asphodelaceae: Asphodeloideae) 1: A review of the T. thyrsoidea group (Section Trachyandra) including three new species from the Northern Cape
    (2010) Boatwright, James S; Manning, J C
    Three new species of the genus Trachyandra are described, T. hantamensis Boatwr. & J.C.Manning, T. kamiesbergensis Boatwr. & J.C.Manning and T. sanguinorhiza Boatwr. & J.C.Manning. These species form part of a group of morphologically similar species referred to here as the T. thyrsoidea group and are distinguished by their generally small stature, filiform leaves (except for T. tortilis), and simple or shortly branched racemes of patent flowers with maculate tepals. Many of the species in the group have roots that contain abundant anthraquinones, visible as a red substance below the outer skin of the roots, and which is soluble in alcohol, thus often staining herbarium papers purple. A synopsis of the eight species that comprise the T. thyrsoidea group is presented, with maps of each species and illustrations of those described as new.
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    Variation in seed set amongst populations of a redent pollinated geophyte, Colchicum coloratum
    (2009) Kleizen, C; Midgley, J J; Johnson, S. D.
    Agricultural activities around the rural village of Nieuwoudtville in the Succulent Karoo region of South Africa has lead to the confinement of many plant and animal species to fragmented patches of relatively untransformed habitat. The geophyte Colchicum coloratum subsp. coloratum (Colchicaceae) was studied in five patches of variable size in and around Nieuwoudtville. This species is dependent on rodent visitation for seed production. The influence of variation in population size and plant size on seed set was investigated, as well as whether there is pollen limitation in this species. A pollen-supplementation experiment indicates that there is pollen limitation in C. coloratum, and that much of the natural seed set could be the result of pollinator-mediated selfing. The five populations appeared to have different rodent abundances, however, neither population size nor the abundance of rodents in the area have an effect on seed set. This suggests that the mutualism between C. colchicum and its rodent pollinators is robust, and that habitat fragmentation in Nieuwoudtville has not yet affected the seed production of this geophyte.