Biology Reference
In-Depth Information
4.4.1 Ge ne tic Specialists
h e genetic-specialist hypothesis proposes that polyandry evolved as a
mechanism to get a broader distribution of worker genotypes in colo-
nies and thus broader distributions of response thresholds. As a conse-
quence, individuals are self-sorted into performing those tasks for
which they have the lowest response thresholds. Individuals with lower
thresholds will be more likely to perform the tasks repeatedly as spe-
cialists and will become more ei cient. Increased ei ciency is believed
to be the reason division of labor and task specialization evolved in so-
cial insects.
h e genetic-specialist hypothesis assumes that there is genetic varia-
tion for performing tasks, that there is a mechanism (deterministic or
stochastic) for maintaining genetic variation for task performance, that
genetic specialists are more ei cient, and that colonies with more gene-
tic specialists survive and reproduce more than those with fewer spe-
cialists. It is clear from many studies that the genotype of an individual
biases her behavior toward dif erentially performing some tasks.
Within-colony genetic variation has been demonstrated for foraging
for pollen, nectar, and water, dancing on a swarm, guarding the entrance
of the nest, stinging behavior, undertaking, provisioning queen versus
worker cells, the age of onset of foraging, precocious foraging (initiating
foraging behavior very early in life in the absence of older bees), fanning,
worker egg-laying behavior, eating worker-laid eggs, grooming, and
engaging in food exchange. h ere is also some experimental evidence
that polyandry can lead to faster rates of colony growth, better sur-
vival, and production of more males (a component of reproduction)
than colonies with single-mated queens. However, we still lack a suf-
i cient model to explain the maintenance of genetic variation for task
performance and a clear demonstration of increased ei ciency in ge-
ne tic specialists.
4.4.1.1 A Model for the Maintenance of Variation and the Evolution of
Polyandry
Clearly, genotypic variability and polyandry are not neces-
sary for division of labor within colonies because single individuals
