Biology Reference
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of all four sources. Only two traits varied, not more than expected due
to chance with so many comparisons. h e distributions of the ranks of
the means (1-5 corresponding to the i ve treatment groups, four single
sources and one combined source) for the 19 traits revealed that the
high-diversity colonies had more intermediate ranks for traits. Genetic
variation made the colonies more average.
4.5 A Pluralistic View of the Evolution of Polyandry
It is unlikely that a single model can explain the evolution of polyandry
in honey bees, much less all the Hymenoptera. Instead, it is likely that
there are multiple explanations. h e potential ef ects of diploid drone
production on mating-behavior evolution have been clearly demon-
strated. But the mechanism of sex determination cannot explain the
high levels of recombination in bees because the production of diploid
males is a consequence of a single gene, and, therefore, recombination
has no ef ect. So, there must be additional benei ts derived from in-
creased genetic variation. h e other hypotheses are more consistent
with high levels of recombination as long as the traits involved are poly-
genic. Selection to avoid parasites and pathogens probably has played a
role but probably is not a gene-for-gene relationship of host and para-
site. It is more likely that broad-based, polygenic resistance is involved;
however, the empirical results are still equivocal. h e generally higher
performance of more genetically diverse colonies has been clearly dem-
onstrated. We know that the general ef ects are in addition to any ef-
fects of polyandry on the consequences of producing diploid males and
are distinct from the ef ects on parasites and pathogens. We still do not
know to what degree there is a need for rare genetic specialists, a need
for a broader distribution of genetically programmed specialists, or a
need for colonies to be near average states for as many traits as possible
in order to avoid failure.
