Figure 2: Hypothesized and simulated colonization and dispersal routes.

(a) Hypothesized colonization routes of agamid taxa into Africa via the Sinai (CR1) or the Bab al-Mandab (CR2), the 27 km broad strait between the Arabian Peninsula and the African continent²⁶. Subsequent dispersal of arid taxa into Africa has been hypothesised via arid dispersal corridors such as the North African corridor, the Sahel corridor, and the arid corridor from south-western Africa to the Horn of Africa^24,25,26. Extents of the Sahara desert and Congolian forests were derived from Olson et al.¹². (b–e) Simple dispersal spread patterns (DISP1–DISP4) simulated with KISSMig¹¹, illustrating accessibility of the African continent from the origins CR1 and CR2 (black triangles). The scenarios represent DISP1 (no barriers, equally high suitability across Africa), DISP2 (Sahara desert unsuitable), DISP3 (like DISP2, but Congo forests with low suitability) and DISP4 (like DISP3, but arid corridors with high suitability and other cells with intermediate suitability). For further details of simulations see text and Table 1. Colonization was simulated using the statistical programming language R and maps were created using ArcGIS (version 10.2, ESRI, Redlands, CA, USA).