Commodity canola insect visitation

AbstractThese data were used in a simulation study to examine how honey bees distribute themselves across foraging landscapes. The ideal-free distribution and central-place foraging are important ecological models that can explain the distribution of foraging organisms in their environment. However, this model ignores distance-based foraging costs from a central place (hive, nest), while central-place foraging ignores competition. Different foraging currencies and cooperation between foragers also create different optimal distributions of foragers, but are limited to a simple two-patch model. We present a hybrid model of the ideal-free distribution that uses realistic competitive effects while accounting for distance-based foraging, and test it using honey bees (Apis mellifera L.) foraging in canola fields (Brassica napus L.). Our simulations show that foragers maximizing efficiency (energy profits/losses) prioritize distance to their aggregation more than those maximizing net-rate (energy profits/time), and that social foragers move to more distant patches to maximize group benefits, meaning that social foragers do not approach an ideal-free distribution. Simulated efficiency-maximizers had a hump-shaped relationship of trip times with distance, spending shorter amounts of time in both nearby and far-away patches. Canola fields were far more attractive to simulated foragers than semi-natural areas, suggesting limited foraging on semi-natural lands during the bloom period of canola. Finally, we found that the observed distribution of honey bees in canola fields most closely resembled the optimal distribution of solitary efficiency-maximizers. Our model has both theoretical and practical uses, as it allows us to model central-place forager distributions in complex landscapes as well as providing information on appropriate hive stocking rates for agricultural pollination.
MethodsVisitation, pollen, and nectar data were collected from commodity canola fields in Alberta, Canada during the summers of 2014 and 2015. Observers watched 1m2 plots of for approximately ten minutes and recorded the number of visits to within the plot. They then sampled stigmas from five random flowers, and collected nectar from an additional five random flowers per plot, and counted the density of plant stems per m2. Stigmas were mounted on slides and Brassica pollen was counted, and the volume of nectar was measured along with the nectar concentration. During 2015, the numbers of individual visitors was also counted along with the number of visits, soil water measurements were taken. Additionally, honey bee visitation behaviour was recorded on the flowers: honey bees were recorded as either top-foraging (landing on the top of the flower for foraging) or side-foraging (landing on the side of the flower and drinking nectar from between the petals), and nectar-foraging or pollen-foraging (pollen visible on corbiculae).
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