Underestimated regional species diversity in the Cape Floristic Region revealed by phylogenetic analysis of the Erica abietina/E. viscaria clade (Ericaceae)

Abstract

As one of the largest genera of flowering plants, the richness of species in Erica (Ericaceae) is all the more remarkable because > 80% of the > 800 species are endemic to the smallest floral kingdom, the Cape Floristic Region (CFR) of South Africa. In the CFR, pockets of narrowly endemic taxa appear in close juxtaposition with their widespread and variable relatives. The taxonomic challenges of Cape Erica are epitomized by the complex Cape 'abietina/viscaria clade', currently comprising at least 25 species. We reassess species boundaries and patterns of regional endemism in this clade using a phylogenetic tree inferred from multiple nuclear ribosomal and plastid DNA sequences. We show that the seven currently recognized subspecies of E. abietina represent at least three independent, morphologically distinct lineages with non-overlapping geographical distributions. We resurrect the name E. grandiflora to include E. abietina subsp. aurantiaca and subsp. perfoliosa and we provide a new name for E. abietina subsp. petraea (E. situshiemalis). This means that E. abietina is now an additional endemic species for the Cape Peninsula, including the natural World Heritage Site, Table Mountain National Park.