Phylogeographic analyses of western Palearctic Scaurus (Coleoptera: Tenebrionidae) reveal undetected taxonomic substructure along the pre-Saharian Atlantic Coast of western Africa

Phylogeography stands as a key tool to explore evolutionary patterns and processes, playing a crucial role in delimiting evolutionary units. Identifying these units is essential for providing robust taxonomic decisions. In this study, we present a comprehensive phylogeographical framework of Scaurus uncinus (Forster, 1771) and Scaurus gigas Waltl, 1835 across the Iberian Peninsula and North-western Africa, where they are widely co-distributed, coexisting in several localities on both sides of Strait of Gibraltar. Our results show that the Strait of Gibraltar did not act as a geographical barrier for these species, revealing shared mitochondrial haplotypes and nuclear alleles between populations on both sides. However, the Souss Valley in Morocco appears to have historically served as a significant geographical barrier within the S. gigas lineage, leading to the divergence of two morphologically distinct sublineages, one to the north ( S. gigas ) and the other to the south ( S. ferreri stat. nov.). In addition, we point out a case of cytonuclear discordance between S. uncinus and S. gigas in the southwest corner of the Iberian Peninsula, suggesting the occurrence of an ancient event of genetic introgression between the two species.