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cating that they correlated with our mapped QTLs. We had coni rmed
them. Consistent with the colony-level pollen-hoarding study, the high
allele for
pln1
resulted in a bias for nectar, not pollen. We also looked at
the ef ects of the QTLs on the sugar concentration of collected nectar.
Bees that inherited the low-strain allele for
pln2
collected nectar with a
signii cantly higher concentration of sugar. h is result was initially very
surprising, but subsequent studies that linked the genetic and pheno-
typic architectures of pollen hoarding with sucrose sensitivity and water
and nectar foraging coni rmed it (Chapter 5).
6.4 Identii cation of
Pln3
We mapped two major quantitative trait loci that explained nearly 60
percent of the total phenotypic variance in our mapping population.
h e mapping population consisted of only 38 colonies derived from the
second generation of our selection program. h is is a very small num-
ber of individuals for a map. Normally you want many more. Merideth
Humphries was appointed to do another map. Kim Fondrk set up the
crosses from the i t h generation of the selection program using the
same design as for the i rst map. h is time the population consisted of
153 colonies headed by super-sister high-strain queens mated to hybrid
drones. Phenotype data were taken 10 to 12 weeks at er introduction of
the queens to the hives. Two years later, the resulting QTL map re-
vealed a new pollen-hoarding QTL that explained about 10 percent of
the total phenotypic variance. We named it
pln3.
Like the
pln1
QTL,
the high allele of
pln3
resulted in less stored pollen. Independent verii -
cation of
pln3
was done as for
pln1
and
pln2.
During two sampling periods, we collected nearly 400 returning
foragers derived from a high-strain backcross and examined them for
marker alleles linked to
pln3.
h e two sampling periods dif ered mark-
edly with respect to the availability of l oral resources, which was re-
l ected in the results. Individuals that inherited the low-strain allele for
pln3
collected larger pollen loads in one sampling period, larger nectar
loads in the other sample period, and nectar loads with lower sugar
concentrations in both periods. Clearly
pln3
was af ecting foraging be-
