Cape plants reveal how and when landscapes and climates evolved along the South African coast

What is it about?

The evolutionary history and relationships of plants across the Cape Mountains can tell us about how and when landscapes changed in the past, and further reveal major shifts in ancient climates

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Why is it important?

Geoecodynamics exploits the historical signals in the DNA of genomes of species to reconstruct the tempo and mode of evolutionary events in landscapes over geological timescales. This methodology is inherently ecological, as it exploits fidelity of species for landscape patches as determined by the niches of respective species. This study mined the genomic record of 12 "Cape Clades" - comprising a total of 553 species. Each of these clades is a genus (such as Protea) that stands out in its richness of endemic species, which are confined to respective habitat patches in the landscape. Collective analyses of all 12 clades recovered and striking patterns in associations of species with discrete habitat categories, as mapped by abiotic variables: namely gradients in climate, altitude, and the different geological units. Molecular clocks of the phylogenies (calibrated gene trees) enabled dates to be confidently assigned to the evolutionary shifts revealed in speciation events and occupation of new niches. The interesting congruence obtained in this study for so many independently evolving species of the Cape flora reinforces confidence in the consilience of the collective results, which reconstruct paleoenvironmental evolution across the Cape Floristic Region over the past 23+ million years. Augmenting research methods in the earth sciences, the geoecodynamic methodology deepens our understanding of the origins of a biodiversity hotspot, with new insights into the evolution of Cape climates and landscapes.