Climatic oscillation during the Quaternary resulted in fragmentation of
once more continuous ancient floras and a series of invasions of different
floras into the Pondoland Centre in response to climatic change, with some
elements invading more than once. This implies both a temporally complex
and a floristically complex origin for the extant flora of the Centre. Data
derived from analysis of the melange of extant floristic elements in the
Pondoland Centre is presented in support of this hypothesis. A synfloristic
comparison of Oribi Gorge (OGNR) and Umtamvuna Nature Reserves (UNR)
is the basis for this study.
A comparison of the species lists generated for OGNR and UNR
reveals that 24% of the 1514 angiosperm species are shared. The familial
composition of the reserves is similar, with eight of the ten most diverse
families contributing a similar proportion of species to the respective floras,
with the exception of Acanthaceae. The ten most diverse families comprise a
comparatively small proportion of the respective floras; this is indicative of
high diversity over long geological periods, i.e. of refugia. Analysis at the
generic level revealed similar consistancy between the two gorge floras.
Approximately 4% of the UNR species and 2.3% of OGNR species are
Pondoland Centre endemics. Approximately 40% of the endemic species are
shared by the gorges. Data reveals that both palaeoendemic (predominantly
woody, forest taxa) and neoendemic (predominantly herbaceous or
suffrutescent, grassland taxa) species occur. The Pondoland Centre is thus a
refugium for species trapped on the Msikaba Group sandstones as a result of
climatic oscillation during the Quaternary, and a centre of neoendemism.
OGNR and UNR floras include Cape, Afromontane and tropical
elements (11.3%, 2.8% and 19.1% respectively for OGNR and 16%,3.4%
and 15.3% respectively for UNR). Seventy - two percent of Afromontane
species are shared, indicating a relatively recent invasion(s) and lor the
relative proximity of the gorges to the Afromontane flora. The lower species
overlap in the Cape element (39.2%) of the two gorges implies that the
invasion of the element is ancient, with subsequent extinction of many of the
taxa from OGNR in response to climatic change. It is also possible that this
invasion was initally less successful; fewer species found refuge in OGNR.
The tropical element comprises the largest proportion of the flora in both
gorges and many (ca. 50%) of the species are shared. The degree of species
overlap indicates that the invasive flora was either initially more similar or that it is tess prone to extinction. The level of overlap could also suggest that the
invasion was more recent than that of the Cape taxa. The tropical element is
larger in OGNR and the Cape element is larger in UNR. This is partly due to
the gorges' respective proximities to the tropical and Cape floras. This trend
is echoed in the endemic data.
iv
The conservation status of the endemics and of the Pondoland
vegetation types is established and recommendations for further research are
made. The data support the establishment of a larger UNR, the maintenance
of both Umtamvuna and Oribi Gorge as formal nature reserves and the
establishment of a new reserve (or reserves) within the Pondoland Centre. / Thesis (M.Sc.)-University of Natal, Pietermarizburg, 1998.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10342 |
| Date | January 1998 |
| Creators | Meter, Edna Beatrice. |
| Contributors | Edwards, Trevor J. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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