Table 1 Predictor variables to explain spatial variation in species richness of agamid lizards across Africa.

Simulated dispersal (accessibility)

 DISP1

Simulated dispersal into a homogeneous environment (all grid cells with suitability s = 1), i.e. accessibility (simulated number of first occurrences) from colonization areas at Sinai and Bab al-Mandab (compare Fig. 2)

Locations of colonization areas from Wagner²⁶, simulation of accessibility with KISSMig¹¹

 DISP2

Simulated dispersal (i.e. accessibility) as in DISP1, but Sahara desert masked as unsuitable (s = 0)

Extent of Sahara desert biome from Olson et al.¹², origin of colonization from Wagner²⁶, simulation with KISSMig¹¹

 DISP3

Simulated dispersal (i.e. accessibility) as in DISP2, but Congo forests with low suitability (s = 0.2)

Extent of Sahara desert and Congo rainforest from Olson et al.¹², origin of colonization from Wagner²⁶, simulation with KISSMig¹¹

 DISP4

Simulated dispersal (i.e. accessibility) as in DISP3, but arid corridors with high suitability (s = 1) and other cells with intermediate suitability (s = 0.5), except Sahara desert (s = 0) and Congo forests (s = 0.2)

Extent of Sahara desert and Congo rainforest from Olson et al.¹², arid corridors and origin of colonization from Wagner²⁶, simulation with KISSMig¹¹

Current climate

 TEMP

Annual mean temperature (°C × 10)

Worldclim dataset⁶¹

 TEMP MAX

Maximum temperature of the warmest month (°C × 10)

Worldclim dataset⁶¹

 TEMP MIN

Minimum temperature of the coldest month (°C × 10)

Worldclim dataset⁶¹

 PREC

Annual precipitation (mm yr⁻¹)

Worldclim dataset⁶¹

 PREC DRY

Precipitation of driest month (mm)

Worldclim dataset⁶¹

 PREC SEAS

Precipitation seasonality: coefficient of variation of monthly values (mm)

Worldclim dataset⁶¹

Paleoclimate

 LGM TEMP

Anomaly in annual mean temperature between Last Glacial Maximum (c. 21,000 years ago) and present (°C × 10)

Calculated in ArcGIS as the difference between current annual mean temperature⁶¹ and annual mean temperature during the Last Glacial Maximum, the latter as a mean of the CCSM3 and MIROC3.2 models from the PIMP 2 project⁶⁵, downloaded from Worldclim

 LGM PREC

Anomaly in annual precipitation between Last Glacial Maximum (c. 21,000 years ago) and present (mm yr⁻¹)

Calculated in ArcGIS as the difference between current annual precipitation⁶¹ and annual precipitation during the Last Glacial Maximum, the latter as a mean of the CCSM3 and MIROC3.2 models from the PIMP 2 project⁶⁵, downloaded from Worldclim

 PLIO TEMP

Anomaly in annual mean temperature between late Pliocene (c. 3 mya) and present (°C × 10)

Calculated in ArcGIS as the difference between current annual mean temperature⁶¹ and annual mean temperature during the late Pliocene⁶⁶, the latter resampled in ArcGIS with a bilinear interpolation to the resolution of the current data

 PLIO PREC

Anomaly in annual precipitation between between late Pliocene (c. 3 mya) and present (mm yr⁻¹)

Calculated in ArcGIS as the difference between current annual precipitation⁶¹ annual precipitation during the late Pliocene⁶⁶, the latter resampled in ArcGIS with a bilinear interpolation to the resolution of the current data

 MIO TEMP

Anomaly in annual mean temperature between late Miocene (11.61–7.25 mya) and present (°C × 10)

Calculated in ArcGIS as the difference between current annual mean temperature⁶¹ and annual mean temperature during the late Miocene³⁹, the latter resampled in ArcGIS with a bilinear interpolation to the resolution of the current data

 MIO PREC

Anomaly in annual precipitation between late Miocene (11.61–7.25 mya) and present (mm yr⁻¹)

Calculated in ArcGIS as the difference between current annual precipitation⁶¹ and annual precipitation during the late Miocene³⁹, the latter resampled in ArcGIS with a bilinear interpolation to the resolution of the current data

Topographic heterogeneity

 TOPO

Topographic heterogeneity: range in elevation (m)

SRTM data⁶⁷ downloaded from Worldclim and processed in ArcGIS