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Continental scale patterns of biodiversity: can higher taxa accurately predict African plant distributions?

journal contribution
posted on 2023-06-07, 17:09 authored by Beverly La Ferla, James Taplin, David OckwellDavid Ockwell, Jon C Lovett
The distribution maps of a total of 3563 species, which represent 8.9% of the known African angiosperm. flora, were entered into cells representing a one-degree latitude-longitude grid of Sub-Saharan Africa. The computer programme WORLDMAP was used to explore continental scale patterns of biodiversity. The maps were used to assess the use of higher taxa as a surrogate measure for predicting patterns of species richness. Genera were found to predict species richness distributions most closely, with higher taxa (families, orders, subclasses) exhibiting progressively worse correlations. However in two areas, the Cape Region of South Africa and coastal Cameroon, there was a higher species to genus ratio than in other areas of Africa. In the Cape Region this meant that generic richness failed to predict species richness. Hotspots, defined as the 5% of grid cells with the highest scores for richness and range-size rarity, were identified for species and higher taxa. Whilst a high percentage of species richness hotspots were predicted by higher taxa, there were important exceptions like the Cape Region. Species range-size rarity hotspots were not well predicted by higher taxa. Hotspots of higher taxa (families and orders) do not therefore accurately predict the location of species hotspots. Higher taxa appear to provide a powerful and accurate tool that can be used to predict large scale patterns of species biodiversity in Sub-Saharan Africa. However care must be taken when using taxa higher than genera, especially if selecting areas of highest conservation priority. The special case of the Cape Region indicates the danger of extending predictive generalizations as the ecological mechanisms that promote and retain species may not be the same in all places.


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  • Published


Botanical Journal of the Linnean Society







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  • Geography Publications


The paper assesses the classificatory tools to hand from computer maps to establish the extent of plant biodiversity for sustainability. If the aim is to gauge biodiversity at the species level, then higher taxa (especially families and orders) become increasingly misleading as a guide to hotspots across Africa. The issue is relevant to selecting priority areas for e.g. climate change policy implementation, and has been widely cited in this field. Dr Ockwell was responsible for updating the continent-wide species database, re-running all the statistical analysis and re-writing and submitting the paper on that basis.

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