Commodity canola and seed canola visitation and plant data

Insect-mediated pollination of crops is an important service to
agriculture, as increased insect visitation can increase fruit production
by increasing pollen deposition. Unfortunately, pollination is often
treated as a “black box”, and pollination management suffers from key
knowledge gaps that hinder its greater utility, particularly the specific
mechanisms underlying the processes of visitation, pollination, and fruit
production. We present a causal model that links insect visitation to
pollination to three separate components of yield, using field data from
two types of canola (Brassica napus) production systems. Our results
demonstrate that yield in commodity canola fields is primarily determined
by plant size, and we found no relationship between honey bee (Apis
mellifera) visitation and pollen deposition, or pollen deposition and seed
yield. In contrast, yield in seed production canola fields was similarly
controlled by plant size, but there was also a strong relationship between
alfalfa leafcutting bee (Megachile rotundata) visitation and pollen
deposition, as well as pollen deposition and seed yield. Leafcutting bee
visitation in particular strongly increased pollen deposition in seed
canola fields, whereas honey bee visitation did not. This model serves as
a step towards a dynamic model of pollination services and highlights the
relative importance of bee pollination in canola production.