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Keywords:

  • Birds;
  • Cape Floristic Province;
  • endemics;
  • Fynbos;
  • Heinrich events;
  • hosing experiments;
  • last glacial stage;
  • South Atlantic;
  • species distribution models;
  • Succulent Karoo

Abstract

Aim

To explore the magnitude and spatial patterns of last glacial stage orbitally forced climatic changes and suborbital climatic fluctuations in southern Africa, and to evaluate their potential roles in determining present biodiversity patterns.

Location

Africa south of 15° S.

Methods

Palaeoclimate scenarios for southern Africa were derived for 17 time slices using outputs from HadCM3 atmosphere–ocean general circulation model experiments, including five designed to mimic Heinrich events. Species distribution models for birds of Karoo (45) or Fynbos (31) were used to simulate species' potential past distributions. Species-richness patterns were assessed for each time slice, and minimum species richness for regional endemics of each biome determined for each grid cell. Areas of greatest ‘stability’ for endemics of each biome were identified using grid cells with greatest minimum richness.

Results

Simulated suborbital climatic fluctuations were of greater magnitude than orbitally forced changes and had anomalies of opposite sign in many areas. The principal local drivers of suborbital fluctuations were marked contrasts in South Atlantic circulation and temperature between experiments mimicking Heinrich events and those with only slow forcings. These contrasts in ocean circulation and temperature were consistent with marine sediment core evidence of changes in the South Atlantic coincident with Heinrich events in the North Atlantic. Whereas orbitally forced last glacial climates generally resulted in range expansions and increased species richness in many grid cells compared with the present, the contrasting conditions of Heinrich events resulted in much reduced ranges and species richness, especially for Karoo species. Very few grid cells remained suitable for larger numbers of endemic species of either biome under all palaeoclimate scenarios examined, but this minority of ‘stable’ grid cells correspond to present diversity centres.

Main conclusions

Suborbital climatic fluctuations during the last glacial stage were probably of considerable magnitude in southern Africa. This may account for apparent inconsistencies between regional palaeoclimate records, as well as being key to determining present biodiversity patterns.