Biology Reference
In-Depth Information
combs. He looked at the other colonies with piles of chewed wax in
front and observed the same phenomenon. All the colonies displaying
this behavior had sister queens who had been mated to drones derived
from their mothers. He put new combs in, and they chewed them as
well. h ey even chewed through cells that contained larvae and pupae
and cast them out of the hive. Inbreeding, such as mating these queens
to drones from their own colony, increases homozygosity at individual
gene loci. Traits that are recessive and normally rarely seen, such as the
genes for hygienic behavior, become homozygous, and the traits are ex-
pressed. Harry Laidlaw told me that he also had an inbred line at one
time with the same behavior. He never saw the trait except when he in-
bred. h e same is true in our experience.
4.4.3 Other Evidence for the Genetic-Specialist Hypothesis
Several studies have attempted to do direct tests comparing colonies
with multiply inseminated queens with those with queens that are sin-
gly inseminated. Most of the studies have controlled the sources of
queens and drones used for insemination so that the single- and multiple-
insemination groups have been balanced with respect to genotypes
(Figure 4.6). For example, drones are taken from several lines, or queen
sources, and are used for single insemination of sister queens. h en other
sister queens are inseminated with sperm derived from equal contribu-
tions of drones from combined pairs of sources or all sources pooled.
Colonies headed by queens that were singly inseminated with sperm
from males from dif erent lines or queen sources are compared. Ob-
served trait dif erences among drone sources suggest genetic variation
for the traits. h en the queens with pooled sperm from multiple sources
(the more genetically diverse groups) are compared with the averages
for the individual sources from which the drones were combined for
insemination. Deviation from the expected average values of the indi-
vidual sources suggests an ef ect of genetic variation, a consequence of
the interactions of the genotypes. Experiments of this type have failed
to give clear demonstrations of ef ects of genetic diversity on colony
traits. h e reasons for failure could be the limited number of drone
