Biology Reference
In-Depth Information
QTLs
(pln1, pln2, and pln3)
that af ected the weight of nectar and pol-
len collected. Foraging loads of nectar and pollen are linked; they are
not independent. We have collected thousands of foragers at entrances
of hives, taken their loads, and weighed them. h ere is always a nega-
tive correlation (Figure 2.12). Bees with larger loads of pollen collect
smaller loads of nectar, and vice versa. h erefore, these three QTLs are
af ecting the joint loading of pollen and nectar by foragers, as assumed
in the model. Although the underlying genetic basis of observed varia-
tion in foraging for nectar and pollen is surely more complex than our
model, the model does contain the essential elements: (1) there is gene-
tic variation in populations for pollen and nectar collecting; (2) at least
two genes are af ecting foraging behavior; (3) both genes af ect both
pollen and nectar loads; and (4) there is no single optimum genotype.
As a consequence, if the genetic specialists are better at foraging and
this af ects colony i tness, then polyandry should evolve.
4.4.1.3 Behavioral Evidence for the Model
Are ge ne tic specialists bet-
ter? h e model assumes that this is the case and that polyandry is a
mechanism to increase their numbers in a colony. In order to test for
task performance of task specialists with dif erent genotypes, we took
advantage of the behavioral plasticity of honey bee foragers from strains
of bees that were selected for the amount of surplus pollen they store,
the pollen-hoarding strains (see Chapter 5 for complete description).
Workers from the high-pollen-hoarding strain tend to specialize in
pollen foraging, while those from the low-pollen-hoarding strain tend
to be nectar specialists. However, there is a broad overlap in the forag-
ing behavior of high- and low-strain bees. Some high-strain bees show
a bias for nectar, and some low-strain bees bias their foraging toward
pollen. Overall, the average foraging tendencies are dramatically dif er-
ent, but there is still much variation. h erefore, we were able to test in-
dividuals derived from each of these two strains as task specialists for
both tasks.
h e work described here was done by Gui Deng, a doctoral student
in the laboratory of Keith Waddington. Waddington and I have col-
laborated over the years, and he spent two full-year sabbaticals in my
