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atures turn on i rst, followed by those with progressively higher
thresholds.
h eoretical models and studies of thermoregulation in colonies
with more or less genetic variation due to dif erent numbers of sub-
families have validated the graded-response hypothesis. Colonies with
multiple subfamilies of workers (more fathers) are better able to main-
tain a constant temperature and respond better to increasing tempera-
tures (are more resilient) than are colonies with a single father because
individuals with increasing response thresholds to temperature respond
and fan as the temperature increases, yielding a gradual response of the
colony as a whole.
3.8.2 Stored Pollen
Colonies show great resilience to disturbance of stored pollen quanti-
ties. When stored pollen is added to a colony, foragers collect less pol-
len until the added surplus is consumed. If stored pollen is removed,
foragers collect more pollen until its level is restored. h is occurs through
individuals increasing their foraging ef ort for pollen by collecting
larger loads and making more frequent trips (individual plasticity) and
through the recruitment of new individuals into pollen foraging (col-
ony plasticity). A low pollen-foraging stimulus results in a higher de-
gree of dif erentiation among subfamilies, where fewer subfamilies col-
lect larger shares of the incoming pollen. A high stimulus results in the
recruitment of new pollen foragers from across a broader representa-
tion of subfamilies (like fanning behavior with high temperatures dis-
cussed in Section 3.8.1); it exceeds the response thresholds of a broader
group of individuals. h ese results are consistent with the response-
threshold model for colony plasticity and resilience.
3.8.3 Undertaking Behavior
Undertaking behavior does not demonstrate the same level of individ-
ual and colony plasticity or resilience. Gene Robinson and I tested the
behavioral plasticity of workers and colony resilience in response to
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