Nativists who favor “native pollinators” often believe that these insects – bees, butterflies, moths and similar insects – rely on native plants. The plants and insects co-evolved, goes the argument; and so to protect one, you must plant the other.
We came upon a recent article in the journal Nature that notes such specific interdependent relationships are rare. There’s a good reason: it would make both plant and insect vulnerable to changes in the weather or other environmental factors.
Instead, plants are pollinated by a variety of insects (and even birds); and these same pollinators use a number of different species of plants.
Including non-native ones.
WHAT’S BEST FOR BEES
In the article, “The Pollinator Crisis: What’s Best for Bees” author Sharon Levy starts by describing numerous bees, native and non-native, buzzing around a patch of red flowers.
“All these insects are drawn to a clump of red vetch (Vicia villosa), an invasive weed. Just down the road is a patch of native lupins, laden with purple blossoms. But the lupins bloom in silence: no bees attend them.”
The article (which was reprinted in the Scientific American) is based on the work of a number of researchers, including Alexandra Harmon-Threatt (who just finished her doctorate at UC Berkeley) and Rachel Winfree of Rutgers. (In case you want more information, the article cites published research on plants and pollinators from a number of scientists.)
A BUMBLE BEE’S POINT OF VIEW
Harmon-Threatt looked at it from a bumble-bee’s viewpoint. She studied three species of bumble-bees, and analyzed the pollen they’d collected. Instead of favoring particular plants, she found that they looked for quality and quantity of pollen.
“What matters to most bee species is the abundance and quality of pollen — and if an introduced plant, such as the red vetch, offers more protein-rich food than the natives around it, the bees will collect its pollen.“
A pollination expert quoted in the article agrees. “Until the past five or ten years, people thought that exclusive pollination relationships were more common,” Rachel Winfree of Rutgers says. Instead, they found that bees collect pollen from plants in proportion to how common the flowering plants are in the landscape. “I don’t see why bees would know or care whether a plant was native or exotic,” Winfree says, according to the article.
WEEDS, BLOOMING WEEDS!
So what do pollinators want? In a word, weeds.
We’ve seen this for ourselves in San Francisco. The early-blooming oxalis and ivy and the winter-flowering eucalyptus provide food for pollinators of all sorts and the wildlife that depends on them. As we described in our article Interwoven and Integrated: Native and Non-native Species in Life’s web, the so-called “invasive species” that the Sutro Stewards and the Significant Natural Resource Areas Program are trying to destroy are in fact rich and valuable habitat in our ecosystem.