Molecular characterisation of honey bees, Apis mellifera subspecies in East Africa

Abstract

Honey bee, Apis mellifera subspecies from East African populations were evaluated for phylogenetic relationships using mitochondrial markers. Apis mellifera scutellata, A. m. litorea and A. m. monticola were found to have a close genetic relationship and are largely indistinguishable. However, based on elevation three groups were documented; lowland, mid-altitude and highland bees. Apis mellifera populations from Kenya, Uganda, Tanzania and Madagascar out-group were also genotyped at 8 microsatellite loci. The average mean number of alleles and the average mean observed heterozygosity were high at 8.201±2.5035 and 0.781±0.00346 respectively, for all populations. Mean genetic diversity per locus and population was high at 0.783 for all populations indicating a high capacity for adaptation to harsh conditions such as drought, diseases and pests. A low overall mean population differentiation value of 0.056±0.04 signified moderate levels of structuring and genetic differentiation among populations. The probability values for genetic assignment of individual to populations were less than 0.5 indicating that the populations are not isolated and there is substantial hybridization. Results of clustering, admixture, genetic diversity attributed to variance and phylogenetics showed that the dynamics of the honey bee subspecies in East Africa is associated with a relatively stable population demographic structure, especially in unfragmented habitats, natural forests and mountainous regions. In these areas, the results suggest a lively demographic historical pattern of their existence characterized by recent evolutionary expansions and no bottlenecks. Association studies showed that on average colonies stored more nectar (69%) than pollen (31%). There is positive correlation between sting and pln (0.184458) suggesting that defensive colonies forage for nectar more than the less defensive ones. Candidate gene search identified three genes each associated with foraging (GB46589, GB44258, GB44259) and stinging behavior (GB48999, GB49000, GB55730). The knowledge of genetic relationship, admixture analysis and candidate gene identification amongst African honey bee subpecies is crucial for harnessing their economic important traits for selective breeding, conservation and productivity efforts.