Abstract:
AIM : Although existing bioregional classification schemes often consider the
compositional affinities within regional biotas, they do not typically incorporate
phylogenetic information explicitly. Because phylogeny captures information
on the evolutionary history of taxa, it provides a powerful tool for
delineating biogeographical boundaries and for establishing relationships
among them. Here, we present the first vegetation delineation of the woody
flora of southern Africa based upon evolutionary relationships.
LOCATION : Southern Africa.
METHODS : We used a published time-calibrated phylogenetic tree for 1400
woody plant species along with their geographical distributions and a metric of
phylogenetic beta diversity to generate a phylogenetic delineation of the woody
vegetation of southern Africa. We then explored environmental correlates of
phylogenetic turnover between them, and the evolutionary distinctiveness of
the taxa within them.
RESULTS : We identified 15 phylogenetically distinct biogeographical units, here
referred to as phyloregions. The largest phyloregion broadly overlaps with
Savanna vegetation, while the phyloregion overlapping with the south-western
portion of the Fynbos biome is the most evolutionarily distinct. Potential evapotranspiration
and mean annual temperature differ significantly among phyloregions
and correlate with patterns of phylogenetic beta diversity between
them. Our phylogeny-based delimitation of southern Africa’s woody vegetation
broadly matches currently recognized phytogeographical classifications, but also
highlights parts of the Namib Karoo and Greater Limpopo Transfrontier Park
as distinct, but previously under-recognized biogeographical units.
MAIN CONCLUSIONS : Our analysis provides new insights into the structure and
phylogenetic relationships among the woody flora of southern Africa. We show
that evolutionary affinities differentiate phyloregions closely resembling existing
vegetation classifications, yet also identify ‘cryptic’ phyloregions that are as evolutionarily
distinct as some of the recognized African vegetation types.
