Maternal diversity patterns of Ibero-Atlantic populations reveal further complexity of Iberian honeybees

Dissecting complex diversity patterns typically exhibited by organisms of hybrid zones is among the greatest challenges in evolutionary biology. This has been a long-standing goal of numerous Iberian honeybee studies. Herein, we further contribute to this goal by a fine-scale maternal survey of the Portuguese honeybee populations. In addition to confirm a predicted African ancestry of Portuguese populations and negligible levels of C-lineage introgression, our fine-scale survey revealed unparalleled levels of African maternal diversity and a remarkable north-south cline formed by African haplotypes of distinct ancestry. This survey further highlights the distinctiveness of A pis mellifera iberiensis by showing the existence of highly contrasting diversity patterns between the Atlantic and Mediterranean populations. Our findings further support an ancient natural invasion of the Iberian Peninsula possibly by Apis mellifera intermissa and also by Apis mellifera sahariensis. Protecting this African legacy is of unquestionable importance, especially with Iberia becoming warmer and dryer.