Thesis (MSc (Botany and Zoology))--Stellenbosch University, 2008. / Sequence data from the Internal Transcribed Spacer (ITS) of the nuclear ribosomal
DNA were used to study the phylogenetic relationships in the genus Ursinia Gaertn.
(Asteraceae, Anthemideae) in the southern African region. Closely related genera, i.e.
Cotula L., Osteospermum L. and Agoseris Raf., were used as outgroups. The study
also included maximum parsimony and principal component analyses.
The taxa within the genus Ursinia had previously been classified into two subgenera,
Ursinia and Sphenogyne R.Br., mainly on the basis of distinct cypsela characters. The
maximum parsimony, principal component and the phylogenetic analyses revealed
two subgenera, corresponding to the existing subgeneric classification. Principal
component analysis shows that the pappus, the number of pappus bristles and the
colour of the cypsela are the most informative characters.
However, the low number of phylogenetically informative characters of the ITS
sequences, the poor resolution in the consensus tree, and low branch support values
indicate that the ITS data contain weak phylogenetic signals. The low bootstrap values
for many nodes suggest that one should be cautious in using the ITS region alone to
make final conclusions about the origin and evolution of taxa. In maximum parsimony
analysis, the RI, CI and bootstrap values are low; principal component analysis values
are also low. Furthermore, there is a lack of resolution in subgenus Sphenogyne. In the
literature, Ursinia is divided into seven series but they were not retrieved as
monophyletic in this study, probably because of short branch lengths in the
phylogeny. Further molecular data are therefore required to be able to support or
reject the present classification. Maximum parsimony, principal component and
molecular analyses show that U. trifida f. calva Prassler and U. trifida (Thunb.)
N.E.Br. f. trifida are not sister taxa, supporting the recognition of these two taxa as
separate species.
The Ursinia taxa from the summer-rainfall region are not monophyletic and are sister
to a clade of Cape species. This supports a hypothesis that Ursinia migrated from the
Cape into the Drakensberg which has been shown for a number of other Cape groups
that have Drakensberg relatives.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1793 |
| Date | 12 1900 |
| Creators | Swelankomo, Nonkululeko |
| Contributors | Mucina, Ladislav, Bellstedt, Dirk U., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | Stellenbosch University |
Page generated in 0.0024 seconds