Introgression in native populations of Apis mellifera mellifera L: implications for conservation

Abstract

Hybridisation and introgression can have negative impacts on regional biodiversity through the potential erosion of locally adapted lineages. The honey bee (Apis mellifera L.) occurs in twenty-seven subspecies across Europe, is an extremely economically important insect, yet threatened by multifarious impacts. Transhumance of the most commercially appealing varieties threatens native honey bee diversity by introgression and subsequent loss of locally adapted traits, or even by complete removal of some subspecies from parts of the range. Here levels of admixture and introgression are examined in UK honey bees suspected to be from hives of the dark European honey bee (Apis mellifera mellifera). Microsatellite DNA and STRUCTURE analyses reveal that the studied populations are generally admixed, and discriminant analysis of principal components shows them to be intermediate between A. m. mellifera and A. m. carnica populations. However, examining mitochondrial haplotype data (COI-COII intergenic spacer region) and nuclear DNA reveal that some hives are relatively pure (from four to fifteen hives, depending on the Q-value threshold). Genetic diversity is relatively high in comparison with other European populations. Implications for conservation and management are discussed.

Investigation of free-living honey bee colonies in Ireland

“…An additional factor creating risk for the continued survival of native subspecies is the replacement of native with imported honey bee strains by beekeepers. The presence of non-native breeding stock and hybrid strains such as A. m. carnica and A. m. ligustica (C-lineage) and cross-lineage commercial hybrids such as 'Buckfast' has resulted in large-scale introgression between these and native bees reducing the population of pure A. m. mellifera and altering its genetic integrity, leading to the strong possibility that genes for locally adapted traits may have been removed from the population (De la Rua et al, 2009;Ellis et al, 2018;Jensen et al, 2005;Parejo et al, 2018;Pinto et al, 2014;Randi, 2008;Soland-Reckeweg, 2006). In the midst of efforts to address such issues mentioned above in the managed honey bee cohort there has been insufficient investigation into the status of wild honey bees leaving considerable uncertainty about their current state (e.g., abundance, distribution, longevity) and conservation need (Moritz et al, 2005;Nieto et al, 2014).…”

When One’s Not Enough: Colony Pool-Seq Outperforms Individual-Based Methods for Assessing Introgression in Apis mellifera mellifera

“…Because there is no standard method in use for colony pooling in honey bee introgression studies, it is important to consider the information that different sampling strategies convey. For example, some studies have used multiple sampling of drones [ 20 , 32 , 33 ]. Sampling drones is effectively a maternity test (drones develop from unfertilized eggs), and does not carry information about patrilines present within the colony.…”

“…Introgression levels vary throughout Europe, and a few remaining areas where introgression remains low have been described, for example, in Ireland [ 27 ], the Inner Hebrides (Scotland) [ 20 , 28 ], the Netherlands [ 28 ], and Norway [ 20 , 28 ]. As a result, numerous studies have focused on assessing introgression of the C lineage into A. m. mellifera [ 18 , 20 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

Motivations underpinning honeybee management practices: A Q methodology study with UK beekeepers

“…Black bee farmers, who also agree with this statement but cannot afford to lose colonies, treat breeder colonies only if perceived Varroa load is particularly high, treating their productive colonies (those used to generate an income through honey) prophylactically. Breeder colonies are used to select and breed Amm queens, which are upheld as native to the UK (Carreck 2015 ), with claimed superior Varroa resistance/tolerance (Pinto et al 2014 ; Ellis et al 2018 ; Hassett et al 2018 ). Interestingly, some participants within the conventional hobbyists, and all within the new-conventional hobbyists also tended to agree with the statement in interview, but it does not tend to influence practice due to the prioritisation of other motivations (responsibility to prevent disease spread, and desire for strong, healthy bees); providing depth and nuance to the documented ‘treatment adherent’–‘treatment sceptic’ divide (Thoms et al 2018 ).…”