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Slide 2 of 17
The model presented in the previous slide show already assumes an exponential
decline in bud opening as seed set increases. This assumption was based on the
results of our monitoring studies in commercial seed fields.
Letís add one more assumption to the model, based on a common ecological
principle: that percent mortality of the bee larvae increases as population size increases. This
happens because diseases and parasites are attracted to and build up more
rapidly in large populations than small populations.
In this case Iíve assumed that survivorship ranges from 80% in small bee
populations (similar to values found in healthy populations of Canadian
alfalfa leafcutting bees) to 30% in large bee populations. These are
representative values, and may not be accurate for all fields. However, the
general pattern should hold over different ranges of survivorship, as long as
survivorship decreases as bee populations increase.