Prior to beekeeping, *A mellifera* subspeciated into a number of races in Africa and
Europe, but there was no sharp genetic transition between each race--their
genetics overlapped between races. Yet they still developed into
morphologically, behaviorally, and genetically-identifiable races.
That isn't how Arias & Sheppard describe it:
Traditionally, intraspecific taxonomy of the honeybee, Apis mellifera, has been based on morphology. The subspecies are also described as ‘‘geographic races’’ because their distributions correspond to *distinct geographic areas* ranging across tropical, subtropical, and temperate climates in Africa, the Middle East, and Europe. According to Ruttner (1992), 25 subspecies of A.mellifera can be recognized based on morphometric measurements, biogeography, and behavior.
*The high number of subspecies may result from a number of mechanisms that isolated populations and permitted and accumulation of genetic differences. In Europe such isolation probably accompanied refugia formation during Pleistocene glaciation (Ruttner, 1992).*
In Africa it is likely that climatic changes including desertification and vegetation shifts, factors considered quite important in explaining a number of African faunal distributions (Potts and Behrensmeyer, 1992), were responsible for subspecies diversification. The extant ‘‘relic’’ distributions of the subspecies A. m. sahariensis and A.m. monticola in *Saharan oases and isolated mountain forests,* respectively, appear to support this hypothesis.
The extent of genetic variability may be the result of a great number of individuals in an ice age refugium or the existence of multiple small refugia where populations accumulated genetic changes during this time and then later coalesced into what is now considered A. m. mellifera . Subsequently, these honey bees colonized northern Europe.
notes: Here we have the concepts of refugia and isolation as the primary driver of speciation. It is entirely plausible that were it not for honey bee transhumance, the African population could have further evolved into a separate species from A. mellifera (European) and A. cerana (Asian), given time and isolation.
¶
In the same article they discuss the Italian/Carniolan issue:
Meixner et al. (1993) described introgression of morphological and mitochondrial markers between A. m. ligustica and A. m. carnica populations in northeastern Italy, Slovenia, and Austria. Therefore, Italy seems to be a region where substantial evidence of subspecific introgression occurs. Although this may occur naturally, we can not ignore the role of humans and extensive apiculture in this region on the introduction and selection of particular lineages.
Molecular Phylogenetics of Honey Bee Subspecies (Apis mellifera L.) Inferred from Mitochondrial DNA Sequence
M. C. ARIAS AND W. S. SHEPPARD. USDA-ARS, Bee Research Laboratory, Building 476, BARC-E, Beltsville, Maryland 20705
MOLECULAR PHYLOGENETICS AND EVOLUTION Vol. 5, No. 3, June, pp. 557–566, 1996
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