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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.
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