For the last several years I have been studying the pollination ecology in Birds Hill Provincial Park focusing specifically on the rare Western Silvery Aster (Symphyotrichum sericeum) plant. I discovered that this species is self-incompatible (meaning it can’t fertilize its own eggs), and visited by a wide range of insect pollinators, including both flies and bees.
I also discovered that although this rare plant competes for pollinators with the much more common Showy Goldenrod (Solidago nemoralis) plant, a negative effect on seed production only occurs when their blooming periods overlap.
My first thought was that reducing the number of Showy Goldenrod plants in the community would result in more insect visitations for the rare plant but then I reconsidered as this did not intuitively seem like the right course of action. I wondered if removing plants would actually end up reducing the local insect population by reducing the quantity of nectar available. Perhaps the plants aren’t really competing at all but rather working together to support their mutual pollinators throughout the year. I also considered that any plant species that completes its flowering before Western Silvery Aster begins blooming would not be competing with it for pollinators at all. In fact, you could argue that the common plants facilitate insect visitation to the rare plant by providing nectar to their shared pollinators. Purple Prairie Clover provides nectar to Western Silvery Aster’s pollinators in July.
I decided to test this hypothesis by recording the insect visitors to other plant species before Western Silvery Aster even begins to flower. So far I have obtained some interesting results. One of the most important insect visitor species, a bumblebee (Bombus bifarius), was observed visiting five species of plants in June and July in addition to Western Silvery Aster. A second species, a bee fly (Anastoechus barbatus), was observed as early as July 12th, pollinating three other plant species. It appears that when plants share pollinators, staggered flowering helps to (a) decrease competition, and (b) sustain pollinating insects throughout their active season.
I think that there is a tendency for western scientists to place too much emphasize on competition when interpreting the results of their research. We need to remember that co-operation, if it results in both species increasing their offspring, is also a beneficial strategy for survival.