Pollinator networks and plant communities
Different landscapes support different pollinator networks. Pollinators thrive in landscapes that are flower-rich and capable of feeding them. Likewise, no plant community can survive for long without the right
mix of pollinators. Plants that reproduce each year by seed (annuals) are most vulnerable, and benefit from favoring specialized pollinator species that nest nearby. Perennials can grow and spread asexually for years without producing viable seeds, so they respond slowly to a loss or change of pollinators.
Perennials nevertheless often use energy store in roots, bulbs and corms to produce colorful, fragrant pollen rich flowers that attract diverse pollinator species from a large area (up to a kilometer or two) and can stimulate intense competition among early arrivals when the pollen begins to ripen.
In competition for pollen, size is a factor. When a bumblebee descends on a flower other insects flee. Some bee species are aggressive and will tussle with competitors, behavior that some flies mimic. Other bees and flies timidly wait, resting near high-value flowers until they can sneak a sip of nectar and a lick of pollen. Or they must be content with smaller, less pollen-rich flowers that require more effort to harvest. The more pollen a bee collects before autumn, the more eggs it can provision in its nest; for a hover-fly, the more generations it can produce.
Bombus melanopygus, Lopez Island
Specialized pollinators must time their emergence each year to the timing (phenology) of their host plant. This can be a challenging task in a changing climate. Generalist pollinators must try not to emerge before the flowering season begins. They must also avoid emerging too long
after the first spring blooms, because they will lose harvesting time. In the Salish Sea, flowers are not only beginning to bloom earlier, but they finish much earlier—by the end of June in some years, leaving 2-3 months of summer weather with little for bees or hover-flies to eat. Shorter growing seasons increase competition for pollen. Earlier and shorter seasons tend to coincide with windy and relatively cool spring weather, which favors strong, cold-tolerant fliers.