Autogamy and allogamy have originated independently several times.
(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.
A comparable shift from allogamy
to autogamy was achieved in Vitis (grape): Wild species and some primitive cultivars (dioecious) are cross-pollinators, whereas more modern cultivars (hermaphrodite) are self-pollinating (Olmo, 1995).
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.
Variation of allogamy rate among worker runs according to visitation order.
This low allogamy tendency is confirmed by the 17.5% allogamy rate resulting from the visit of 10 flowers of the D-23 line by B.