Systematic significance of bulb morphology of the Southern African members of Oxalis L. (Oxalidaceae)

Gebregziabher, Awot Kiflu (2004-12)

Thesis (MSc)--Stellenbosch University, 2004.

Thesis

ENGLISH ABSTRACT: The systematics of the southern African members of the genus Oxalis L. (Oxalidaceae) is in a state of flux. The bulbs of these species contain potential taxonomically important characters and therefore require detailed study (Salter, 1944). A pilot study assessed the homology of bulbs among southern African Oxalis species (Gebregziabher, 2001), and found that they are all homologous structures. This pilot study also emphasized the range of potentially informative characters from different bulb parts. The aim of the present study was to assess the taxonomic significance of bulb morphology in selected southern African Oxalis species. As far as possible, efforts were made to represent both the taxonomic (Salter, 1944) and palynological diversity (Dreyer, 1996) present in the genus. Detailed bulb morphological studies of 30 species of southern African Oxalis species revealed 41 potentially informative characters. Different bulb-types were identified based on these characters. Bulb-type affinities of taxa included in this study, as well as bulb descriptions from the pilot study (Gebregziabher, 2001), were discussed. Comparison with the current taxonomic classification (Salter, 1944), palynological classification (Dreyer, 1996) and a preliminary phylogeny based on the non-coding plastid trnL-trnF DNA region (Oberlander, 2003), were also made. Bulb morphology conflicted with the current taxonomic classification (Salter, 1944), but showed greater congruence with both the palynological groupings and the trnL-trnF based phylogeny. Based on this study, bulb morphology is found to be taxonomically significant. Further studies on the bulb morphology and anatomy of southern African Oxalis species are merited. Key words: bulb morphology, Oxalis, informative characters, basal plates, fleshy leaves, tunics

AFRIKAANSE OPSOMMING: Die sistematiek van die suider Afrikaanse lede van Oxalis L. (Oxalidaceae) is labiel. Die bolle van hierdie spesies sluit potensieel taksonomies belangrike kenmerke in, en behoort daarom in detail bestudeer te word (Salter, 1944). In Loodsstudie het die homologie van die bolle van die suider Afrikaanse Oxalis spesies ge-evalueer (Gebregziabher, 2001), en gevind dat hulle homoloë strukture is. Resultate van hierdie loodsstudie het ook die reeks van potensieel informatiewe kenmerke van verskillende boldele beklemtoon. Die doel van hierdie studie was om die taksonomiese belang van boImorfologie in geselekteerde suider Afrikaanse Oxalis spesies te ondersoek. Pogings is aangewend om, sover moontlik, beide die taksonomiese (Salter, 1944) en die palinologiese (Dreyer, 1996) diversiteit van die genus in die studie in te sluit. Gedetailleerde bol-morfologiese studies van 30 suider Afrikaanse Oxalis spesies het 41 potensieel informatiewe kenmerke uitgewys. Gebaseer op hierdie kenmerke, is verskillende bol-tipes geïdentifiseer. Verwantskappe tussen die bol-tipes van die spesies ingesluit in hierdie studie, sowel as beskrywings van bolle volgens die loodsstudie (Gebregziabher, 2001), word bespreek. Vergelykings met die huidige taksonomiese klassifikasie (Salter, 1944), palinologiese klassifikasie (Dreyer, 1996) en In voorlopige filogenie gebaseer op die niekoderende plastied trnL-F DNA-streek (Oberlander, 2003) is ook getref. BoImorfologie weerspreek die huidige taksonomiese klassifikasie (Salter, 1944), maar toon groter ooreenstemming met beide die palinologiese groeperings en die trnL-F gebaseerde filogenie. Hierdie studie het bevind dat bolmorfologie van taksonomiese waarde is. Verdere studies op die bolmorfologie en -anatomie van die suider Afrikaanse Oxalis spesies word aanbeveel.

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