Species-level phylogenetic reconstruction of the African cycad genus Encephalartos (Zamiaceae)
This thesis explores species-level phylogenetic relationships of the African cycad genus Encephalartos, which is one of the eleven genera of cycads. The genus is confined to Africa and comprises approximately 65 species, 38 of which are found naturally in South Africa. The phylogenetic studies on Encephalartos to date still result in many unresolved polytomies so it is not possible to fully understand the relationships between different taxa. In this study, AFLPs were used together with DNA sequencing to reconstruct the phylogenetic relationships of the genus. This study is the first to be presented with aims of resolving the relationships of Encephalartos using AFLPs together with DNA sequences. Total DNA was extracted from accessions sampled from the Kirstenbosch Botanical Garden and the Montgomery Collection, representing the majority of Encephalartos species listed in the most recent world list of cycads. Sequences of the trnL intron, rpoC1, ITS 1, ITS 2, and AFLP profiles from two sets of selective primers were used to reconstruct the phylogenetic relationships within the genus using maximum parsimony methods. As in earlier studies, unresolved polytomies were recovered from the sequencing data. The AFLP trees have some resolution but CI and RI indices were low indicating high levels of homoplasy in the data. The relationships resolved by this study for all the data sets separately and combined were different to those previously suggested for the genus. The biogeography of Encephalartos is also investigated by habitat optimization of the genus to estimate the origin of the genus with respect to its current distribution.
Phylogeny, Evolution (Biology), Zamiaceae, Evolution
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