In searching for more recent info about honey bee ancestry and mtDNA, I
found a very interesting article. I don't know if most people can access it,
so I have quoted it a bit. It is certainly worthwhile to read the whole
thing. I know I learned a lot!

Excerpts, quoted for the purpose of review:

THE AFRICAN HONEY BEE: Factors Contributing to a Successful Biological Invasion

By Stanley Scott Schneider, Gloria DeGrandi-Hoffman, and Deborah Roan Smith

The African honey bee subspecies Apis mellifera scutellata has colonized
much of the Americas in less than 50 years and has largely replaced European
bees throughout its range in the New World. The African bee therefore
provides an excellent opportunity to examine the factors that influence
invasion success.

One of the more remarkable aspects of the African bee is its ability to
displace European honey bee subspecies in the New World. Initially, it was
assumed that African and European bees would interbreed, giving rise to the
"Africanized honey bee" of Latin America. However, although substantial
hybridization occurs when African bees invade areas with European
populations, over time European characteristics tend to be lost.

Indeed, throughout much of its range in the New World, the invading honey
bee population has remained essentially African in its nesting biology,
swarming and absconding behavior, foraging and diet selection, and
mitochondrial DNA (mtDNA) characteristics.

Study of geographic variation in the mtDNA of honey bees has revealed four
geographic lineages of mtDNA mitotypes, or unique sequences, within A.
mellifera: west European, east European, African, and Middle Eastern.

The different subspecies of honey bees interbreed to produce viable, fertile
offspring. The introduction of A. m. scutellata into Brazil therefore
initiated the beginning of a grand, unplanned experiment on the relative
fitness of European, African, and African/European hybrid honey bees in the
wild, in apiaries, and under a variety of climatic conditions.

[It is] possible to infer ancestry of African populations in the New World,
and the gradual expansion of the African population from Brazil to the
United States has provided a time series of older to younger feral African
populations.

[The] studies have shown that (a) there is a high frequency of African mtDNA
in feral African populations, in some cases to the near exclusion of
European mtDNA; (b) feral African populations may show evidence of paternal
gene flow from European sources, but the frequency of European alleles
gradually decreases in long-established feral African populations; and (c)
the European alleles that persist over time are predominantly of west
European rather than east European origin.

[The] hybrid-swarm concept was seriously challenged when mtDNA polymorphisms
revealed that over 97% of feral colonies from Brazil, Venezuela, Honduras,
and Mexico possessed African mtDNA haplotypes; east European mitotypes were
virtually absent. Because honey bee mtDNA is maternally inherited without
recombination, this indicated that feral African colonies were matrilineal
descendants of African bees, most likely A. m. scutellata.

Although European queens in managed colonies were mating with African
drones, European-matriline  (Africanized) swarms escaping from apiaries were
clearly not a major component of the feral African populations in the
regions sampled.

African populations in Brazil have been in contact with European honey bees
since the 1950s and thus have had more time than any other African
population in the Americas to accumulate European mtDNA. However, 35 years
after the introduction of African bees into Brazil, 100% of 126 hived feral
swarms carried mtDNA characteristic of A. m. scutellata

Thus, even in areas where hybridization and introgression of European genes
have been particularly likely, European mitotypes have dropped to low
frequencies, especially in the feral population.

A major puzzle in the African bee invasion is the differential persistence
of west versus east European alleles in the feral population and the extent
to which this phenomenon will continue as the African bee colonizes North
America. The greater persistence of west European alleles may be related to
the question of hybrid inferiority.

West European alleles may be more compatible than east European alleles with
a mostly African genome or may confer some advantage in particular habitats.
Alternatively, the west European markers that persist in the New World may
represent neutral alleles that introgressed early in the invasion process in
Brazil and may have only minor effects on the behavior and biology of the
African population.

Nest usurpation is a form of social reproductive parasitism in which small
African swarms invade European colonies, replace the resident queens, and
cause the complete and instantaneous loss of European matrilines. Annual
usurpation rates have been reported at 5% in Venezuela and 0%–40% in
different regions of Mexico. In southern Arizona, annual usurpation rates
can reach 10%–25%. Nest usurpation has therefore been speculated to play an
important but regionally variable role in the spread of African bees in
Latin America and may contribute to the loss of European matrilines in the
United States.

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