I have just had a phone conversation with someone who attended Dr.
Hoffman's talk in California. The info that I got was that there may be a
misunderstanding. It may not be that the African bee in US has capensis
genes, but that that they exhibit similar traits. This ability of workers
to raise queens from worker eggs is not restricted to capensis at all but
has been observed even in European bees, and other insects. Probably the
discovery of this trait is due to the intense scrutiny that the bees have
been subjected to here in the US. Further, it came up in our conversation
that this trait could probably be developed in any line of bees, if that
were desired.

Additional background info:

>Nest Defense Behavior in Colonies from Crosses Between Africanized and
>European Honey Bees
>Gloria DeGrandi-Hoffman, Anita Collins, Joseph H. Martin, Justin 0.
>Schmidt, and Hayward G. Spangler

excerpts:
>The most evident behavioral difference between European honey bees (Apis
>mellifera L.) (EHB) and Africanized honey bees (A. mellifera scutellata)
>(AHB) is colony defensive behavior (Stort, 1975; Collins and Kubasek,
>1982; Collins et al., 1982). Unlike EHB colonies, which often mount low or
>moderate responses to intruders, the response of AHB colonies to
>disturbance is usually extreme. It is not uncommon for hundreds or even
>thousands of worker bees to attack a perceived intruder when an AHB colony
>is disturbed.
>
>Two AHB colonies captured in swarm traps (Schmidt and Thoenes, 1990) in
>Tucson, AZ, in 1994 were used as the AHB parent colonies (hereafter
>referred to as AHB-I and AHB-2). Honey bees in the United States are
>characterized as Africanized based upon morphometric analysis (Rinderer et
>al., 1993). The AHB-I and AHB-2 parent colonies used in this study each
>had a probability of Afficanization of 1.0. [100%] Mitochondrial DNA
>(mtDNA) analyses were conducted to determine the matfiline of the parent
>AHB colonies (Smith, 1988; Sheppard et al., 1991). Workers from AHB-1 and
>AHB-2 exhibited the EcoRl mtDNA haplotype common in most African races,
>including Apis mellifera scutellata (Smith, 1988).
>
>The inheritance of defensive behavior in honey bees has been the subject
>of numerous studies (Collins et al., 1984, 1987, 1988; Guzman- Novoa and
>Page, 1993, 1994). Our findings were similar to these reports in which
>most of the workers responding to colony disturbances were AHB hybrids
>(GuzmanNovoa and Page, 1994). This occurred even when a small number of
>AHB workers drifted to another colony as in the case of EHB-1. The most
>defensive colonies in our study were those with AHB patrilines, yet the
>reciprocal cross created the least defensive colonies. These results
>support the hypothesis that queen genotype has little effect on colony
>defensive behavior (Guzman-Novoa and Page, 1993). Our data also indicate
>that defensive behavior is a genetically dominant trait that might also be
>influenced by a paternal factor (Guzman-Novoa and Page, 1994).

http://gears.tucson.ars.ag.gov/publ/defense.html