A systematic revision of Zygophyllum (Zygophyllaceae) in the Southern African region

Van Zyl, Loretta (2000-03)

Dissertation (PhD)--University of Stellenbosch, 2000.

Thesis

ENGLISH ABSTRACT: The previous revision of Zygophyllum L. by Van Huyssteen (1937) included all known species of the cosmopolitan genus Zygophyllum. The present study deals with the species of Zygophyllum occurring in the southern African region which includes Angola, Namibia, Botswana and South Africa. The majority of Zygophyllum species occur in the arid and semi-arid, western parts as well as in the interior parts but some species do occur to the south of the area where milder climatic conditions are experienced. Zygophyllum species are typically described as shrubs or shrublets, rarely herbaceous annuals or biennials, with simple, sessile leaves or sessile, bifoliolate or petiolate, bifoliolate leaves of a succulent texture. Macromorphological as well as phytogeographical data were studied in order to delimit the taxa and to determine their relationships as well as their distributions. Various tables summarizing diagnostic characters of taxonomic importance as well as line drawings depicting the salient features of the species are given. The division of the genus Zygophyllum into two subgenera was investigated and this division is corroborated with additional evidence concerning floral, fruit and seed morphology. The absence or presence of an elaiosome on the seeds found in the two subgenera reflects on their different dispersal strategies. The structure of the morphologically different mucilage produced by the seeds of the two subgenera is touched on. The division of the subgenera Agrophyllum (Neck.) End!. and Zygophyllum, each into several sections, was investigated. Two sections, one from each subgenus, were transferred: the monotypic § Morgsana (Huysst.) Van Zyl to subgenus Zygophyllum; and the monotypic § Grandifolia Eng!. to subgenus Agrophyllum. The § Prismatica Van Zyl is newly described and the §Annua Eng!. is reinstated. seventeen new species are described, a few names sunk into synonymy and several name changes made.

AFRIKAANSE OPSOMMING: Die vorige hersiening van Zygophyllum L., deur Van Huyssteen (1937), het alle bekende spesies van die kosmopolitaanse genus Zygophyllum ingesluit. Die huidige studie handel slegs oor die Suider afrikaanse Zygophyllum-spesies wat in Angola, Namibië, Botswana en Suid-Afrika voorkom. Die meerderheid Zygophyllum spesies groei in ariede en semi-ariede dele aan die weskus asook in die binneland van die area maar sommige spesies groei ook in die suide van die gebied met 'n meer gematigde klimaat. Zygophyllum-spesies word beskryf as struike of halfstuike, is selde kruidagtige, een- of tweejariges en het gewoonlik eenvoudige, sittende blare of sittende verdeelde of gesteelde verdeelde, sukkulente blare. Makromorfologiese en geografiese data is bestudeer om die verskillende taxa af te baken, om verwantskappe tussen die onderskeie spesies vas te stel sowel as om die verspreiding vir elke takson aan te gee. Tabelle met die vernaamste taksonomies kenmerke asook lynsketse van die mees belangrike kenmerke van die verskillende species word verskaf. Die verdeling van Zygophyllum in twee subgenera is ondersoek en is, met behulp van bykomende blom-, vrug- en saadmorfologiese inligting, volkome regverdig bevind. Die aan- of afwesigheid van elaiosome op sade dui op verskillende saadverspreidings metodes. Die morfologies-verskillende slymlaag wat deur die saad van die twee subgenera produseer word, is kortliks beskryf. Die verdeling van die subgenera Agrophyllum en Zygophyllum in verskeie seksies is ondersoek. Die monotipiese subseksie Morgsana word na subgenus Zygophyllum en die monotipiese § Grandifolia na subgenus Agrophyllum verskuif. Die § Prismafica word as nuut beskryf en die § Annua word in hergebruik geneem. Sestien nuwe spesies word beskryf, enkele name word in sinonimie geplaas.

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