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Natural hybridization has been frequently reported in Cactaceae, but there are few studies on the impact of hybridization in the evolution and diversification of this family. The majority of the studies that have addressed this subject have been restricted to the subfamily Opuntioideae. Little is known about the role of hybridization on the more diverse subfamily Cactoideae. This paper discusses putative examples of hybrid lineages in subfamily Cactoideae, focussing on examples of lineages for which hybrid or introgressive origin have been confirmed or deduced from morphological and molecular studies. These examples suggest that natural hybridization may have played an important role in the evolution and diversification of taxa in Cactaceae, and further studies of hybrid lineages may provide us with important insights on the evolution of this family.
The shrubby members of the Mesembryanthema are still poorly known and further field work and study of herbarium material has led to the recognition of eight new species. Seven of these species are placed in the Ruschioideae: Phiambolia longifolia Klak, Phiambolia similis Klak, Ruschiella cedrimontana Klak, Ruschia albida Klak, Ruschia magnifica Klak, Leipoldtia gigantea Klak and Hammeria cedarbergensis Klak. In addition, one species of Mesembryanthemoideae, Mesembryanthemum bulletrapense Klak, is described here. Five of these species are found in the Cedarberg area, whereas L. gigantea and M.bulletrapense occur in Namaqualand. Furthermore, two new names and one new combination in Mesembryanthemum are published, which replace recently published homonyms.
In alpha-taxonomic terms the Eastern Cape Province of South Africa, which includes the entire Albany Centre of Endemism, is one of the richest succulent plant regions in the world. The mild climate of the region is also suitable for the cultivation of a number of exotic succulents, several of which have escaped into the natural flora, subsequently becoming naturalised. The five species of Agave L. recorded for the Eastern Cape are here described and illustrated as part of compiling a Flora for the region. The species are Agave angustifolia Haw. var. angustifolia, A. americana L. var. americana, A. sisalana Perrine, A. vivipara L. var. vivipara and A. wercklei F.A.C.Weber ex Wercklé. A key is provided to assist with the identification of the five species.
Starting from fresh studies on D. abyssinicum and D. schimperi in Ethiopia, the members of the genus Delosperma in north east Africa and south west Arabia are re-investigated, resulting in the recognition of seven distinct groups, one of which is described as a new species: D. sawdahense H.E.K.Hartmann spec. nov. from Saudi Arabia. Another group of populations from Eritrea cannot be assessed at present, due to lack of material. A key to the six named taxa is given, and some suggestions for further studies into the origin and evolution of the group are presented.
The author elaborates on the treatment of the genus Maihueniopsis Spegazzini in The New Cactus Lexicon, discusses the identity of M. minuta (Backeberg) Ritter and publishes the northern form of M. glomerata (Haworth) Kiesling as a new subspecies: M. glomerata subsp. hypogaea (Werdermann) G. Charles. An unidentified species from the Sierra Famatina, Prov. La Rioja, Argentina is illustrated and discussed. Photographs of documented plants in habitat and cultivation, together with distribution maps are provided.
The present study focusses on morphological flower characters considered crucial in the supposed transition from HorridocactusBackeberg to Neoporteria Br. & R. sensu Backeberg. Additionally, physiological characters such as photonastic/ scotonastic perianth segment movement and photoperiodism were documented and found to be informative at species level. Differing dimensions of flowers and their critical relationships to other characters, as well as different flowering periods, separate the southern from the northern taxa. In combination with results from a study based on anatomical data in Eriosyce sensu lato published previously by Nyffeler & Eggli (1997), these findings provide strong support for a separation of Eriosycesubgibbosa ssp. clavata (Söhrens ex Schumann) Kattermann from E. subgibbosa (Haworth) Kattermann, and the necessary nomenclatural change is provided. Additionally, several synapomorphies and phytogeography suggest that E. subgibbosa ssp. wagenknechtii (Ritter) Kattermann, ssp. vallenarensis (Ritter) Kattermann and E. subgibbosa ssp. subgibbosa var. litoralis (Ritter) Kattermann (= the former N. wagenknechtii Ritter, N. vallenarensis Ritter and N. litoralis Ritter) seem to be more closely related to the northern species E. villosa (Monville) Kattermann than to the southern E. subgibbosa. When bioclimatic and phytogeographical data were mapped onto the tentative phylogenetic tree resulting from the analysis of the floral characters, these taxonomic conclusions received even stronger support. Eriosyce subgenus Neoporteria was originally published invalidly (Hoffmann & Walter, 2004), a situation which is rectified here by its formal publication. E. clavata ssp. nigrihorrida (Backeberg) H. E. Walter is also presented as a new combination. The position of two closely related taxa of subgenus Neoporteria, E. taltalensis (Hutchison) Kattermann and E. chilensis (Hildmann ex Schumann) Kattermann, is discussed, but their position remains unresolved. The role in evolution played by pollinators, particularly hummingbirds, is discussed.
In the course of studies in the genus Drosanthemum, a population with 15 different designs of petal colouring was found, starting an extensive investigation in search of character sets allowing a species circumscription beyond flower colours. Results allow the recognition of D. speciosum, the type species of D. subg. Speciosa, and its neotypification, as well as the identification of D. pulchrum and D. edwardsiae, all three forming a group of almost smooth-leaved plants.
In November 2007, a group of about 40 international experts on the genus Aloe L. met in South Africa for a workshop to seek consensus on achievable, key objectives for the Aloes of the World Project (AWP). This was the first event of its kind where Aloe alone was approached on this scale. The Aloes of the World Project aims ultimately to compile as much information as is possible to facilitate internet-based scholarly research on the genus. The process and subsequent outcomes of the Pretoria workshop are discussed. Delegates acknowledged that an interim compromise may be achieved initially, where a minimum of essential elements are hosted on the Aluka (African Plants Initiative) website, with later upgrading of the information base in line with ongoing development of Aluka.