African Honey Bees
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African honey bees are those subspecies of the Western honey bee, Apis mellifera, that occur naturally on the African continent and some of the nearby islands. Forms of the same species also occur naturally in Europe. It should be noted that these boundaries are no longer entirely diagnostic, as European forms have been introduced into all inhabitable continents for purposes of apiculture , while one African form is now widespread in the New World tropics. This complication aside, A. mellifera has radiated into four major lineages: African (A, the subject of this entry), west European (M), southeast European (C), and Eastern (O) [1, 10]. Lineage A also has some natural presence outside the African continent; these lineages are not strictly restricted to particular geographic regions as one can see from the influence of the A lineage within the Mediterranean region (see Box 1 in 8).
Apis mellifera scutellata (savannah bee) become famous after Warrick E. Kerr shipped 142 queens from South Africa to Brazil in 1956 with a view to creating a hybrid of subspecies from Europe and Africa better adapted to the climatic conditions in South America. The following year a few swarms escaped and became established in the wild, giving rise to the Africanized honey bee. They flourished and spread out from their area of introduction, reaching the southern USA 33 years later . Instead of blending with already existing populations of European bees, as had been expected, these feral bees maintained their original phenotype and genotype, so that they are not so much Africanized as African, even after decades in the New World . These bees were more defensive and able to outcompete any other subspecies of European origin that they encountered in Brazil.
The greater defensiveness in African honey bee subspecies is mostly in the ancestral state, in contrast to the lower defensiveness of European subspecies the derived state. There is reason to believe that European honey bees, through selective breeding over the centuries, have more docile and therefore easier to manage. Moreover, in order to survive the European winter, the bees require sufficient honey stores, which selects for greater attention to foraging and brood care during the summer at a possible cost to defensive readiness. In contrast, African subspecies have to deal with patchier and more seasonal resources, which allows them be more defensive and to be ready to leave the nest site for a new one at a distance. Such absconding, or nonreproductive swarming, is more expressed in African than in European subspecies .
When African honey bees first began to spread in the New World, it was feared that they would outcompete native bees as a whole, possibly leading to major ecological repercussions and a serious decline in populations of native bees. As it happened, this did not take place, and their ecological impact was much more benign than expected [9365体育网站]. The climatic conditions seem to prevent a further expansion of the African bees into northern states of the USA, and it seems that they will remain restricted to the warmer conditions in the southern states.
The Cape honey bee, A. m. capensis, is famous for her mode of thelytokous worker reproduction. Furthermore, workers of this subspecies have the ability to produce a queen-like pheromonal signal, can activate their ovaries faster than most other subspecies, and have a high reproductive potential . This high reproductive potential became evident after A.m. capensis colonies were transported into the native range of A. m. scutellata, giving rise to a clonal parasitic lineage of the capensis workers .
The higher genetic variability within the African honey bees than in the European subspecies seems to allow for relatively quick evolutionary adaptation . Indeed, morphometric, genetic, and pheromonal data suggest that there is significant local adaptation linked to the particular biomes in which they occur . The genetic data for the subspecies of Madagascar show two distinct clusters linked to elevation and vegetational zones , which is also reflected in the pheromonal data. Similar relationships between pheromonal clusters and vegetational zones were found in A. m. adansonii from Nigeria  and for the Cape honey bee within the Cape floristic region . Moreover, morphometric data of A. m. scutellata show that it is not homogenous across its broad distribution but rather subdivides into distinct morphoclusters. This indicates that A. m. scutellata has adapted to local conditions to form distinct local populations. The greatest of variance mostly occurs at transitional edges of major climatic and vegetational zones and sometimes with more localized discontinuities in temperature .
The high level of local adaptation is most likely a result of the large wild population of honey bees, compared to colonies forming part of any kind of beekeeping activity . Furthermore, the lack of any major breeding programs allows local populations to adapt to local conditions. Such local adaptation results in stable hybrid zones like the one between A. m. capensis and A. m. scutellata in Southern Africa and between A. m. adansonii and A. m. jemenitica in West Africa, among several hybrid zones . Within the native range of the species, Africa seems to be dominated by wild populations, while honey bees in Europe are dominated by bees kept by beekeepers, with very few wild colonies contributing to the genepool in Sweden, France, and the Mediterranean. Wild populations of European honey form a significant part of the gene pool only in the introduced ranges of North America and Australia .
Despite substantial similarities among subspecies of the Western honey bee, especially with respect to ecosystem services, African subspecies seem to be more defensive , workers are more able to reproduce even in queenright colonies [4, 13], and African subspecies seem markedly less susceptible to diseases and parasites .
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