Introgressive hybridisation puts the distinctive population of Apis mellifera mellifera in Ireland at risk: evidence from a multidisciplinary approach

Apis mellifera mellifera a honey bee subspecies at risk of extinction across much of its range has a stronghold in Ireland where it is the native honey bee subspecies and is referred to as the black bee. However, an increase in imports of other subspecies and commercial strains is now a major threat to its genetic integrity. Furthermore, despite assertions by Irelands’ beekeepers that the black bee is a distinct ecotype, little taxonomic work has focused on this population. Here we liaise with beekeepers and assess the managed honey bee cohort for signs of increased introgression. We also investigate morphological variation in A. m. mellifera colonies to establish for the first time a description of this subspecies in Ireland. SNPs and mitochondrial data indicate a further increase in introgression in the population even though much of the population remains A. m. mellifera. The morphology of Irish A. m. mellifera has deviated significantly from European populations and can be characterised as being smaller and hairier, with a broad abdomen, shorter legs and a shorter proboscis. Their fore wings are longer but with a smaller cubital index. These attributes may have evolved as adaptations to the unique environmental and climatic conditions found in Ireland but may also have been influenced by artificial selection and/or genetic drift.