Neither the plant nor the pollinator behaves altruistically. That is, neither plant nor pollinator says to itself, “Self, I’m going to help that poor plant (or pollinator) get the things it needs.”

Instead, those plants that have more of what the pollinator needs are more likely to get pollinated. And once they are pollinated, they pass those same genetic traits to the next generation. Likewise, the pollinators that are best equipped to gather nectar or pollen are most likely to survive and pass their genes to the next generation. As time goes on, the plants and the pollinators become more and more suited for each other.

In her article “Mighty Mutualisms: the Nature of Plant-pollinator Interactions” Carol Landry estimates that plant-pollinator mutualisms involve about 170,000 plant species and 200,000 animal species.

Mother nature can be an extremist sometimes. An extreme form of mutualism, called an obligate mutualism, occurs when the interdependence between a plant and a pollinator is so specific that no other organism can take its place. In other words, one specific pollinator is required to pollinate one specific plant and that pollinator needs that specific plant as well. This is also the most precarious kind of mutualism because if one partner becomes extinct, the other goes as well.

A good example of an obligate mutualism is the yucca plant and the yucca moth. The yucca plant is absolutely dependent on the yucca moth to pollinate its seeds. The yucca moth larvae cannot survive without yucca seeds to eat. The system works because the larvae eat only some—not all—of the seeds.

Plant-pollinator mutualisms are believed to be at least partly responsible for the large diversity of flowering plant species that showed up 90-130 million years ago. A good example of what may seem to be “unnecessary” diversification occurs within the fig family. Approximately 750 species of fig tree are pollinated by approximately 750 species of fig wasps. Most of the wasps pollinate only one or two species of fig, so the mutualisms are very specific. How does this happen?

Think of it this way. Say you have a mountain called Big Rock Mountain. To the east you have a population of flowers called Awesome Red Daisies that are pollinated by bees called Stinging Mothers.

Awesome Red Daisies have 6 really important genes: a, b, c, d, e, and f. All these genes are pretty common except for c. There are only a few c genes in the population—it is a gene that makes the flower yellow.

Stinging Mothers have 8 really important genes: 1, 2, 3, 4, 5, 6, 7, 8. All are pretty common except 2. Gene 2 gives the bees a long tongue. As a rule Stinging Mothers have short tongues, although a few have long tongues.

Life is fine on the east side of Big Rock Mountain until one day a tremendous storm (the biggest storm in un-recorded history) blows some Awesome Red Daisy seeds and a few of the Stinging Mothers to the west side of the mountain.

Oddly enough, most of the seeds that landed in the west were the type that carried the gene for yellow flowers. So when the flowers bloomed in the spring, many were yellow. This was okay with the Stinging Mothers since they could see red or yellow. But the problem was this: the flowers were longer than the ones in the east. It just so happened that there was a genetic trait linked to yellow color that caused the flowers to be long and deep.

As a result of the oddly-shaped flowers, only those bees that had a long tongue were able to collect nectar. All the other Stinging Mothers died from starvation so their genes did not get passed to the next generation. But oddly enough, the gene for long tongue was associated with stinglessness.

After many generations, all the Awesome Red Daisies on the west side of Big Rock Mountain were yellow and all the Stinging Mothers had long tongues and couldn’t sting. After many more generations the flowers and bees on the west side of Big Rock Mountain were so different from those on the east side that they could no longer interbreed. They had become separate species: Awesome Yellow Daisies and Stingless Mothers.

So there you have it. The same type of accidental and random occurrences in nature can cause one species of fig and its pollinator to become 750 species of figs and their pollinators. The changes happen slowly over millions of years, but they have given us the vast biodiversity we are now trying so hard to destroy.

Rusty

Creating biodiversity. New species evolve on west side of the mountain.

The interesting thing about Texas bluebonnets is the bright white spot on the banner (upright portion) of each floret. Bees are extremely attracted to these bright spots and can collect a large quantity of high-quality pollen from the florets. As the florets age, however, the white spots turn a purplish-red and the bees are much less attracted to them as a result. At the same time that the spot changes color, the pollen becomes less abundant, less fertile, and less sticky.

This confluence of events just happens to be good for the bees and good for the plant. It is good for the bees because they can efficiently collect lots of nutritious pollen without having to expend energy checking the purple-spotted florets. In addition, the pollen is so sticky the bees can carry large loads of it back to their hives or nests.

It is good for the plant because it means that the bluebonnets–which are dependent on insect pollinators–are pollinated with fresh, fertile pollen rather than with older, drier, and less fertile pollen. This, in turn, assures that a large crop of high quality seeds will be produced from the flowers. It is definitely a win-win situation–what we call a plant-pollinator mutualism.

In a paper published in The Southwestern Naturalist [1], Schaal and Leverich found that bees can collect up to 150 times more pollen from a white spotted floret than a purple-spotted one. Other research has revealed that nearly all pollinator visits (about 96%) were to the florets with white spots.

Now that you’ve absorbed this cool little tidbit of pollination ecology, you can go back to wondering why on earth Texas has five state flowers. Hmm.

Rusty

[1] Schaal, Barbara A. and Wesley J. Leverich. 1980. Pollination and Banner Markings in Lupinus texensis (Leguminosae). The Southwestern Naturalist 25(2): 280-282.

Texas bluebonnet. Older florets at bottom have already turned dark. Flickr photo by alamosbasement.

Now, many—perhaps most—of the world’s flowering plants are dependent on animal pollinators (mostly bees) and the bees are entirely dependent on the plants. For all practical purposes they are a unit—one cannot survive without the other. Yet many, many people who study one side of the equation totally ignore the other side.

So what is beekeeping really about? What is the heart of it? The answer, of course, is flowers. Beekeeping is all about flowers.

I can’t stress this enough. Beekeepers get so immersed in hive designs and foundation types we forget about how the bees will fill them. We get so distracted with minutia like cell size, frame types, and queen rearing methods that we are blind to what the highway department is spraying on the roadways. We get so competitive with each other we forget that beekeeping is not about us, it’s about “them.” And what does this nebulous “them” have on its mind? Flowers.

Bee life is consumed with one goal: to find, harvest, and store enough food for the next generations. This food comes from one source—flowers—and all colony activity is based on the availability of flowering plants. What we do—treat for diseases, prevent swarming, check for solid brood patterns, and block moisture buildup—is nothing more than an annoyance to the bees that have one thing on their collective mind: flowers.

Whether your passion is gardening or beekeeping, your skill will grow with your knowledge of the other side of this fascinating co-dependency. You don’t need to make a systematic study of it, just appreciate, observe, and respect it. Learn to identify a new flower—or a new bee. Figure out who pollinates what. Watch what is happening overhead as well as underfoot. It will pay off in ways you can’t imagine.

Rusty

It's all about the flowers. Photo by the author.

Honey bees have special body parts where they pack pollen to be carried back to the hive. The parts—one on each hind leg—are called corbiculae or “pollen baskets.” The corbiculae are covered with hairs which help to hold the pollen in place, but very sticky pollen can form large clumps—something that makes provisioning even easier.

The pollen from many wind pollinated plants, such as grass, is much drier and not nearly so sticky. This pollen has to be carried in smaller clumps and so the bees have to make more trips to collect an equal amount, which wastes both time and energy.

It is interesting to note that the pollen in the corbiculae is not the pollen that is transferred to other flowers. The pollen that does that job is the pollen that sticks to the body of the bee and rubs off when she visits the next flower. But pollenkitt facilitates this transfer as well: the pollen sticks to the bee until she rubs up against another flower, and then the pollen sticks there instead.

Plants that are insect pollinated not only have sticky pollen, they have lots of pollen. This provides the win-win relationship that defines plant-pollinator mutualisms. In this case, the plant has to expend lots of energy to produce excess pollen with sticky coatings to attract the bees. In turn the plant gets pollinated. The bees benefit from lots of pollen that is easy to carry home. In addition, pollenkitt contains lipids, proteins, and phenolic compounds which are important to honey bee health.

Researchers have suggested many other reasons for pollenkitt and, in truth, it probably has multiple functions. It may keep the pollen from blowing away or drying out, or it may protect the pollen from ultra-violet radiation and certain pathogens.

Rusty

Nevertheless, the bees don’t have any contracts or business deals with the plants. The foraging bees have a mission, and that mission is to go get something the colony needs and bring it back. The things the hive needs are pollen, nectar, water, and propolis, and there are feedback mechanisms and other communication systems that tell the foragers which of these they need to collect.

So given the mission to go forth and collect pollen, that’s what the forager does. She doesn’t give a rip about what the plant wants. Once she finds a satisfactory source of pollen, she collects it and brings it home. If the pollen comes from a wind-pollinated plant such as corn or alder, it makes no difference to the bee.

Plants that need cross pollination have evolved ways of attracting pollinators, including brightly colored petals, pleasing aromas, or plentiful nectar. (Technically speaking, the plants that had some of these characteristics were able to survive and reproduce more successfully than those which didn’t, so those genes increased in frequency in the gene pool.) In any case, the plants benefited from the insects and the insects benefited from the plants.

Plants that don’t need to attract pollinators usually don’t have showy flowers, nectar, or fragrance. They still need pollen in order to reproduce, but the wind takes care of moving it around. Some of these plants actually produce pollen that is toxic to bees, or that is not pleasing to them. Because producing pollen is energy-expensive for the plants, if they don’t need to share it with insects, it is best if it’s not attractive to them.

When you’re thinking about honey bees, the whole thing is made more complicated by the fact that honey bees are not native to North America, so the plants that are native here did not co-evolve with them. Honey bees are polylectic which just means they forage on many different species of plants. And for the most part, the wind-pollinated plants that produce “tasty” pollen just have to put up with them.

Rusty