4) There have been parallelisms in the evolution of mating systems and shifts from facultative autogamy toward allogamy as well as vice-versa.
To test the hypothesis that predominant allogamy evolved independently several times, I searched for the shortest tree under the constraint that all species with anther-stigma distances greater than 6 mm form a single clade.
Several lineages independently evolved virtually obligate allogamy, whereas others, including those invading disturbed habitats, evolved relatively autogamous mating systems.
Therefore, we can assume that different proportions of bee species result in variations of pollen carryover and allogamy rates.
Due to the low number of hybrid seeds produced, the variability of allogamy rates among bumblebee runs was estimated after grouping the flowers; by five or 10 according to visitation order.