A biogeographic analysis of the seaweed flora of the west coast of southern Africa, from Lüderitz to Cape Agulhas

Bachelor Thesis


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University of Cape Town

A biogeographic analysis of the seaweed flora of the area from Lüderitz to Cape Agulhas was undertaken. Biogeographic patterns were reviewed across 15 geographic regions. A TWINSPAN analysis showed a clear division of the area into two separate species communities. These two communities are the Benguela province, and the western overlap region between the Benguela and Agulhas provinces. The western overlap region was found to be the most diverse. Diversity was shown to decrease with a decrease in latitude. Patterns in endemism among the brown seaweeds follow this trend. In contrast to this, red and green endemics increase with a decrease in latitude. Shore distribution patterns were reviewed, and demonstrated an increase in diversity with a progression down the shore. Among the red seaweeds, this increase, with greater depth was considerable. Species distribution patterns in both shore and shore pool zones were found to follow the same pattern, except for a drop in species in the subtidal fringe pools, which this study concluded was a meaningless concept. These results have been reviewed in relation to present conservation areas along this shore, and future recommendations were made for location of sites for the conservation of seaweed. These were the formation of reserves between Lüderitz and Port Nolloth, between Yzerfontein and Melkbosstrand, and from Scarborough to Cape Hangklip. In some of these areas existing reserves need to make policy adjustments while in others reserves need to be established for the conservation of both diversity and uniqueness of seaweed species.