Reconstructing squamate biogeography in Afro-Arabia reveals the influence of a complex and dynamic geologic past

The geographic distribution of biodiversity is central to understanding
evolutionary biology. Paleogeographic and paleoclimatic histories often
help to explain how biogeographic patterns unfold through time. However,
such patterns are also influenced by a variety of other factors, such as
lineage diversification, that may affect the probability of certain types
of biogeographic events. The complex and well-known geologic and climatic
history of Afro-Arabia, together with the extensive research on reptile
systematics in the region, makes Afro-Arabian squamate communities an
ideal system to investigate biogeographic patterns and their drivers. Here
we reconstruct the phylogenetic relationships and the ancestral geographic
distributions of several Afro-Arabian reptile clades (totaling 430
species) to estimate the number of dispersal, vicariance and range
contraction events. We then compare the observed biogeographic history to
a distribution of simulated biogeographic events based on the empirical
phylogeny and the best-fit model. This allows us to identify periods in
the past where the observed biogeographic history was likely shaped by
forces beyond the ones included in the model. We find an increase in
vicariance following the Oligocene, most likely caused by the
fragmentation of the Afro-Arabian plate. In contrast, we did not find
differences between observed and expected dispersal and range contraction
levels. This is consistent with diversification enhanced by environmental
processes and with the establishment of a dispersal corridor connecting
Africa, Arabia and Eurasia since the middle Miocene. Finally, here we show
that our novel approach is useful to pinpoint events in the evolutionary
history of lineages that might reflect external forces not predicted by
the underlying biogeographic model.