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Taxonomic revision of the Memecylon natalense species-complex in southern Africa.

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Date

2018

Authors

Mona, Imercia Gracious.

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Abstract

iv ABSTRACT Two Memecylon species (M. natalense and M. bachmannii) were previously recognized in southern Africa, and three species of M. section Buxifolia as occurring in Mozambique (M. natalense, M. torrei and M. insulare). However, a recent nrDNA phylogeny revealed that M. natalense as previously circumscribed is not a monophyletic group and includes some geographically outlying populations warranting recognition as distinct evolutionary lineages. In this dissertation, I present the results of a comprehensive morphological study and revision of the ‘M. natalense species-complex’ including the following taxa: M. natalense sensu stricto (endemic to South Africa in KwaZulu-Natal, Eastern Cape, Mpumalanga and Limpopo), M. incisilobum (southern Mozambique), M. nubigenum (southern Malawi), M. rovumense (southeastern Tanzania), M. aenigmaticum (northern Mozambique), M. sp. nov. 1 (northeastern Kwazulu-Natal, South Africa), M. sp. nov. 2 (Eastern Cape province, South Africa), and M. sp. nov. 3 (Limpopo province, South Africa). Although M. bachmannii (Eastern Cape and KwaZulu-Natal) is morphologically distinct, it was also included in the present study because of recent nrDNA work indicating a close relationship with M. natalense. Species boundaries were investigated using phenetic and cladistic methods based on morphology. Phenetic analysis using the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) revealed that M. bachmannii clustered independently, M. sp. nov. 1 clustered close to M. incisilobum, M. aenigmaticum clustered close to M. rovumense, and M. nubigenum clustered close to a subcluster consisting of M. natalense, M. sp. nov. 2 and M. sp. nov. 3. The morphological cladistic results were congruent with a previous molecular analysis in that M. sect. Buxifolia was monophyletic. Memecylon rovumense + M. aenigmaticum and M. incisilobum + M. sp. nov. 1 appeared in separate clades. Memecylon bachmannii and M. nubigenum were each monophyletic, while M. natalense, M. sp. nov. 2 and M. sp. nov. 3 appeared in an unresolved polytomy. Overall, the cladistic results were in agreement with the UPGMA analysis but were less resolved. Vegetative and fruit morphology have proven to be of great diagnostic value in delimiting the members of the M. natalense species-complex. Four new species have been named and described, while a further three new species are proposed. Dichotomous keys are provided, and the conservation status of each species is assessed according to the criteria of the IUCN. A lectotype should be designated for M. natalense. With these additions, the flora of Mozambique now has seven species of Memecylon (including six species in M. sect. Buxifolia). In South Africa, the number of recognized Memecylon species has increased from two to five.

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Masters Degree. University of KwaZulu-Natal, Durban.

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