Pollinators

Above is a bee of the genus Andrena (looks like Andrena dunningi) visiting an ornamental flower in Oak Park, IL.

Pollinators

The vast majority of terrestrial biomes rely on animal pollinators. Angiosperms dominate most terrestrial plant assemblages, and 70-90% of angiosperm species rely on animal pollinators. Although some agricultural species, such as wine grapes and peas, self-fertilize, most domesticated angiosperms benefit from pollination and some require it to set seed. For instance, apples must be pollinated by insects (bees and flies, generally) to set seed and develop fruit, same with cocoa (small rainforest bees and midges), coffee, almonds, and other crops too numerous to mention.

Recently, because of a decline in the abundance of feral and domestic honeybees (Apis mellifera, an exotic species imported to the US from Europe) in the United States and in Europe, a great deal of attention has focused on native pollinators. It is very sad that we have only started caring about these creatures now, because a great deal of the damage has been done, and it will take years for populations of native pollinators to recover, even if we were to act immediately. Native pollinator assemblages have been hit hard by pesticide use, habitat destruction, and changes in farming practices, but still provide many of the pollination services we associate with honeybees, for free, every year. If a figure were set on these services, it would amount to 6-8 billion dollars a year, for the US alone, perhaps more. Native pollinators include, roughly in order of importance, bees, moths and butterflies, flies, hummingbirds, beetles, thrips, and bats. Different ecosystems have different pollinators. Some pollinator-plant relationships are tightly coevolved (an obligate mutualism, or at least an oligolectic pollinator that can only visit one plant), or loosely associated (a facultative mutualism, usually because the pollinator is polylectic, and can visit multiple plants). Most ecosystems have both types, and fortunately, there is often a great deal of redundancy.Above is the halictid bee, Agapostemon virescens, pollinating an ornamental flower in Oak Park, IL.

Bees

There are about 20,000 species of been in the world, including approximately 3500 that inhabit the United States (Goulet and Huber, 1993). The bee fauna of North America encompasses a large number of ecological generalists, as well as many species whose ecologies are specialized to some degree. For example, bees can be polylectic; feeding from, or gathering pollen from a variety of flowers, or be oligolectic; specializing on a limited number of flowers, most likely close relatives. Some bees gather nectar from a wide variety of flowers, but gather pollen from a much narrower subset of the available flora (for an excellent discussion, see Cane and Sipes, 2006). Bees can be univoltine; having one generation a year, or multivoltine; having several. Likewise, bee species differ in their vagility, some being more prone to migrate than others. Some are habitat specialists as well, requiring a particular plant assemblage to be present at a particular time of the year with a particular type of soil for nesting. Nest site requirements vary among bee species. Different taxa of bees may utilize twigs, beetle burrows, sandy soil, packed sand, grassy tussocks, abandoned rodent burrows, the abandoned burrows of other bees, or other nesting substrates. This is an important aspect of bee ecology that is often neglected by agriculturalists. A typical almond orchard is often so systematically flat and homogeneous that ground nesting bees lack opportunities to nest, and even the piles of broken brush and beetle-infested trees that provide nest sites for leafcutter bees, such as orchard bees of the genus Osmia, are absent because orchard managers groom away these features of the landscape. In England, a shift from traditional modes of agriculture to the more Ameicanized, "efficient" modes of agriculture, has been hard on the local Bumblebee species, with many declining severely, because tussocks of grass and rodent burrows have been removed, plowed, and variously "cleaned up" to make room for useful farmland.

Bees are very vagile, and have probably always been prone to what evolutionary biologists call "metapopulation dynamics". A population goes extinct one year, bringing all of its various parasites and hangers-on with it, only to be recolonized by migrants from other populations the next year. Every stretch of habitat is probably being colonized by migrants from outside populations of some species, even as other species go extinct from within. Some of this may be due to the weather, some of it might be pure, random chance. A a mud riverbank that formerly hosted hundreds of bee nests slides into a stream and carries a population of bees with it, a Bombus queen arrives and builds a nest under an overturned flower pot. This temporal variability has always made bees difficult to monitor (Williams et al., 2001). The good news from this is that, if you build it, they will come. An area that has the appropriate resources for bees to survive and prosper will inevitably accumulate species, the same way Mc Arthur and Wilson predicted that oceanic islands, such as Krakatoa, accumulate species from the mainland. The bad news is that an isolated patch of nice-looking wetland or praire will inevitably loose much of its original pollinators over time, with subsequent replacement by an assemblage of pollinators dictated by dispersal, chance, and whatever biotic changes have occurred in the region.

Lepidoptera

To the left is a moth, probably Haematopis gratiara, the chickweed geometer.

Unlike bees, Lepidoptera lay eggs on a host plant (usually, some are decomposers, parasites, or social cleptoparasites), and the larva needs a host plant to grow. Once grown to adulthood, adults rely on nectar for energy. Unlike bees, moths and butterflies do not gather pollen for their own needs-it sticks to them.

Butterflies are wonderful, and they get great press. Probably, every species of butterfly in the world is known, is in a museum somewhere with a pin through it, and has enough enthusiasts that when it begins to decline in numbers, people take notice and start to save it. In the Bay Area, for instance, the endemic San Bruno elfin has enough enthusiasts that the decline of this odd little lycaenid, and its subsequent reappearance, all made news and had the potential to affect public policy. Butterflies, in essence, are just glorified moths, however, and moths don't always get the same press.

Flies

Many groups of flies, including the syrphidae and the bombiliidae are important pollinators. These species feed on both nectar and pollen as adults, and lay their eggs on host plants (syrphidae), or in the nests of their host victims, usually bees, (bombyliidae). Flies almost never get the credit they deserve as pollinators, which is unfortunate, because they are probably more important than anyone guesses. In early spring especially, flies are ubiquitous on flowers.

Others

Beetles, thrips (insect order thysanoptera), hummingbirds (and ecological analogs, such as the unrelated honeycreepers), and bats are also important pollinators.

There are probably three things that people can do to encourage pollinator conservation. One is to buy organic produce whenever it is possible, and to buy produce that was grown via sustainable agricultural practices. The countryside was formerly teeming with habitats for pollinators that simply no longer exist because massive, industrial agriculture and the widespread use of pesticides have simplified the ecosystems to the point that pollinators can no longer find an ecological niche to exist. A second thing is to create friendly situations in their gardens, farms, and parks for pollinators to use as habitats, and habitat corridors, to allow dispersal, and the third, of course, is to support local conservation efforts. Barbara Kremen's work in California has demonstrated that conserved areas serve as source populations of bees, that disperse into agricultural habitats and provide services to humans. Besides beauty, conserved areas provide economic benefits that go beyond the original intentions of the conservationists, and are ultimately important for our survival.

Passage below quoted from: Pollinators Need our Help and Chocolate's Sweet Little Secret (North American Pollinator Protection Campaign)

"The work of pollinators ensures full harvests and seed production from many agricultural crops and provides for healthy plants grown in backyards, community gardens, and other urban areas.

Worldwide, of the estimated 1,330 crop plants grown for food, beverages, fibers, condiments, spices, and medicines, approximately 1,000 (75 percent) are pollinated by animals. It has been calculated that one out of every three mouthfuls of food we eat, and beverages we drink, is delivered to us by pollinators.

More than half the world's diet of fats and oils comes from oilseed crops. Many of these, including cotton, oil palm, canola, and sunflowers, are pollinated by animals.

In the U.S., pollination by insects produces $40 billion worth of products annually.

Pollinators are essential components of the habitats and ecosystems that many wild animals rely on for food and shelter.

Approximately 25 percent of birds include fruit or seeds as a major part of their diet.

Plants provide egg laying and nesting sites for many insects, such as butterflies.

Berries and other fruit form a significant part of the late-summer diet of animals, such as grizzly bears, which fatten themselves in preparation for winter hibernation."

The photos in this post are by Marcus Thomasson, my original field assistant, thank you Marcus....