Out of North Africa: Evolution and biogeography of Afro-Arabian dwarf tarantulas (Theraphosidae, Ischnocolinae)

 

Out of North Africa: Evolution and biogeography of Afro-Arabian dwarf tarantulas (Theraphosidae, Ischnocolinae)

Abstract

Large-scale vicariant events are expected to create congruent phylogeographic patterns among unrelated taxa. A continental-wide disjunction displayed by unrelated plant taxa across Afro-Arabia (the RAND flora pattern) has been traditionally explained as a consequence of late Miocene aridification of the region and the formation of the Sahara Desert. We implement genomic data (UCE), divergence time estimation and biogeographic analyses to uncover the origins of RAND pattern distribution in dwarf tarantula genus Ischnocolus Ausserer, 1871. The results suggest that the disjunct distribution of Ischnocolus resulted from ecological vicariance driven by the Middle Miocene climate cooling, predating the timing of the aridification of the region. Our results thus bring evidence of phylogeographic discordance of the RAND pattern origins among different taxa. Conserved lifestyle and the preference for humid environments among the early diverging Ischnocolus lineages also suggest that dispersal across Afro-Arabia was likely catalyzed by interspecific competitive exclusion. Subsequent lifestyle switches, that enabled the dwarf tarantulas to successfully colonize dry environments, evolved repeatedly in the group’s evolution. Additionally, we delimit the boundaries of the genus Ischnocolus and assess its position within the tarantula phylogeny. As a consequence, we revalidate the genus Luphocemus Denis, 1960, which is endemic to North Africa.

Korba, J., & Opatova, V. (2026). Out of North Africa: Evolution and biogeography of Afro-Arabian dwarf tarantulas (Theraphosidae, Ischnocolinae). Molecular Phylogenetics and Evolution, 108559. https://doi.org/10.1016/j.ympev.2026.108559