Biology Reference
In-Depth Information
change tasks in response to changes in age and colony need, for exam-
ple, changing the loading biases for pollen and nectar in response to
changes in colony stimuli. Colonies with once-mated queens construct
comb, raise brood, and forage for pollen and nectar; in short, they ap-
pear to perform all the normal functions of colonies, even at er strong
selection for single behavioral traits. It is unlikely that a specii c geno-
type is needed in any colony to ensure that any normal task is per-
formed. However, a primary condition for the maintenance of genetic
variability and for the evolution of polyandry as a consequence of geno-
typic ef ects on task specialization is that individuals vary in their value
as specialists as a consequence of their genotypes. For example, indi-
viduals with genotype A are more likely to perform task T
A
and do it
better than individuals of genotype B, while individuals with genotype
B are more likely to perform T
B
and do it better. h ere also cannot be a
single genotype that does both T
A
and T
B
as well as the individual spe-
cialist genotypes.
Assume that the decision to forage for pollen and nectar is controlled
by two independent genes (loci), say,
P1
and
P2.
Each locus has two al-
leles,
h
(high) and
l
(low), where the
h
allele results in a bias toward
collecting pollen and the
l
allele results in a bias toward nectar. h e loci
and alleles are additive and equal in their ef ects. Also assume that the
action of the two loci is based on the ratio of high,
h,
and low,
l,
“doses”
at both loci. For example, individuals with the genotype
P1
h
P1
h
P2
h
P2
h
have four doses of high alleles and will show a stronger tendency to col-
lect pollen than those with a
P1
l
P1
l
P2
l
P2
l
genotype. Individuals with
P1
h
P1
h
P2
l
P2
l
or
P1
h
P1
l
P2
h
P2
l
genotypes will be equivalent and interme-
diate. In order for this model to work, genotypes are not additive across
individuals. For example, a colony composed of equal numbers of for-
agers with a
P1
l
P1
l
P2
l
P2
l
genotype and foragers with a
P1
h
P1
h
P2
h
P2
h
genotype would be better (closer to the optimum uptake of pollen and
nectar) than a colony that is composed entirely of
P1
h
P1
h
P2
l
P2
l
,
P1
h
P1
l
P2
h
P2
l
,
or
P1
l
P1
l
P2
h
P2
h
genotypes, even though there is the same
dose of high alleles in each of the colonies. h e reason they are dif er-
ent is the increase in ei ciency due to specialization, another assump-
tion of the model. If these assumptions are met, there is no single best
