The apparent contradictions and differences of opinion in this string of comments and other related ones may come from trying to generalize and from conflating different types of traits, geographies, time scales, even economies.  "Desirable" outcomes in shifting gene frequencies obviously depend on the genetic basis of a trait, the intensity with which it is being artificially introduced, its survival (and general colony vigor) advantage if not being artificially promoted, the relative sizes of the mating populations with and without the desirable trait at a given time, and probably most importantly whether there is an economic demand for the trait.

It is easy to understand how the high defensiveness in African derived bees spread through the tropics that had low densities of gentler European bees, or they were in pockets, adding the possibility that heightened defense protected colonies from a slew of tropical predators.

Also easy to understand why if you buy a few "resistant" queens, introduce them into an area with high numbers of susceptible genes the "desirable" genes dissipate.  It is also unrealistic to expect that any "survivor" program can succeed in a similar situation of being an island surrounded by an ocean of treated susceptible bees.

One brush does not paint all scenarios.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html