Monday, February 23, 2015

Pollinators and vitamins

We need the vitamins provided by fruits
It is said that bees and other pollinators are responsible for one third of all our food. Whether this is exactly right I do not know; but a trip to the grocery store confirms that a substantial part of our food comes from plants that have been pollinated by insects rather than by the wind: most vegetables and fruits, drinks such as coffee and tea. We even have to include in this list beef, poultry and dairy products because farm animals feed partly on alfalfa or clover which have been pollinated by insects. Without pollinators we would be reduced to eating grains or cereals, potatoes, sea food and fish and very little else (and undernourished beef and poultry).

Tomato flowers
What is never mentioned but I find perhaps even more important than food quantity is quality. Many of our essential vitamins and antioxidants come to us courtesy of pollinators. Vegetables and fruits are loaded with vitamins such as beta carotene, vitamin C and a few others.

More evidence can be found in Contribution of Pollinator-Mediated Crops to Nutrients in the Human Food Supply. Elisabeth J. Eilers, Claire Kremen, Sarah Smith Greenleaf, Andrea K. Garber, Alexandra-Maria Klein. The researchers found that most of the vitamins A, C and E come from crops pollinated by insects. A large proportion of the minerals calcium, fluoride and iron in our diet are also dependent on animal pollination. Lycopene and some antioxidants, β-cryptoxanthin and β-tocopherol, are entirely dependent on insect pollination.

So, in summary, if it wasn’t for pollinators we wouldn’t be one third hungrier. Instead we would be one hundred per cent dead.

Vegetables are indispensable because of their vitamins

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© Beatriz Moisset. 2012

Sunday, February 15, 2015

Before there were flowers: Wind Pollination

Pine tassels. © Beatriz Moisset

Pine cones. © Beatriz Moisset
Maine’s state flower is rather unusual because it is not a flower in the real sense. It is the white pine’s (Pinus strobus) tassel and cone. These are not flowers but serve the same function: the tassels produce pollen that has to arrive at the small, immature cones to produce seeds. Only then the cones can grow and reach maturity. Maine residents must be mighty proud of their pines and for very good reasons. It is a handsome tree of great value, and the tassels and cones, although not as colorful as most true flowers, are quite handsome. I am delighted at this peculiar choice because it serves to illustrate a significant point of pollination.

Long before there were any animal pollinators, only the wind performed this function. Wind pollinated plants have to produce vast quantities of pollen so that just a few grains can arrive to their destination; the immense majority never even come near the female cones and simply goes to waste. Pines, firs, spruce, and other conifers belong to an ancient lineage that appeared long before pollinators entered the scene. Thus they were and still are pollinated by the wind. Despite its inefficiency, this method works well enough when many plants of the same species grow relatively close to each other. This is why conifer forests are composed of only a small number of species. This is also why corn, another wind pollinated plant, needs at least several rows of plants to produce any corn.

Pollen dispersal by wind. © Beatriz Moisset
Getting back to the pine, both the tassel and the cone are well-adapted to their functions, increasing the chances that wind-carried pollen finds its destination. The tassels are placed higher on the tree. The cones are aerodynamically shaped to create small air whirlpools that direct the pollen grains toward the seeds. For millions of years, the land was dominated by these plants, along with even older ones, the seedless ones that reproduce by spores. The more ancient dinosaurs never saw a flower, nor did they care. The flower revolution was yet to come, and once started it would take the land by storm and spread to distant corners. Nowadays, wind pollinated conifers are more common than flowering plants only in harsh and cold environments near polar regions. Most plants everywhere else produce flowers.

The great advantage of flowers and of animal pollinated plants is that pollinators are more efficient than wind alone in transporting pollen to the intended target, thus even if individual plants are far apart, they still succeed at being pollinated. In fact, forests of tropical regions are made largely of blooming trees with so many different species packed in the same space that a pollinator has to travel some distance between members of the same species. So pollinators contribute to biodiversity, which in turn contributes to a more efficient way of using all available ecological resources.

Now I can get on with the story of pollinators of state flowers.

Maine: White pine tassel and cone 

Monday, February 9, 2015

Pollinators of Official State Flowers

A tale of pollinators and pollination

as told by the official state flowers


We love flowers for their beauty and for the impact they have on diverse aspects of our lives. That is why we honor them by choosing an official state flower for each state of the union. A look at the list of state flowers reveals an amazing variety of shapes, colors, perfumes and blooming seasons. Some flowers are open and rather flat; others are elongated, trumpet like, with spurs, or intricately shaped. They may be grouped in clusters or stand alone. They come in a rainbow of colors and their scents are equally varied. Some bloom briefly in just one season, others do it for a longer time.

Why do plants have flowers and why is there such a variety? We seldom think about a flower’s function.  Some even feel that they were put here for our enjoyment. The fact is that their whole purpose is to attract pollinators, those love messengers that carry pollen from blossom to blossom ensuring the development of fruits and seeds and thus the future of the plant’s species. The great variety of flowers is a sign of the diversity of their pollinators. Both the flower and the pollinator complement each other to the point that, in some cases, only one kind of pollinator can perform the job for a particular kind of plant. This mutual fine tuning is the result of a long process of co-evolution. Often one can tell the type of pollinator by looking at the structure of the flower. For instance, flat, open flowers can be pollinated by short tongued insects; longer ones require longer tongued visitors. Tubular flowers are often pollinated by hummingbirds or very long-tongued moths. Night-bloomers are pollinated by night-flyers such as hawk moths or bats.

We often think of the honey bee as the ultimate pollinator and we seldom recognize the fact that many other insects, as well as some other creatures perform that job, in fact many plants have absolutely no use for honey bees. It is true that honey bees are incredibly adaptable and that they visit a wide array of flowers through several seasons, we could say that they are “Jacks of all trades” but we must remember the second half of that saying: “and masters of none”. In many instances flowers fare better in the absence of honey bees because some of them have developed a long standing partnership with their respective pollinators. Honey bees could interfere with such specialized pollinators.

Years ago, I was looking at a book on state flowers and was astonished at their variety. It occurred to me that it was possible to teach an entire course on pollination using state flowers as examples. All it takes is one look at the assortment of state flowers to see that there must be a similar diversity of pollinators belonging to several different groups of animals, not just bees, but also flies, butterflies, moths, beetles, and even bats and birds. Maybe some day, the states will recognize the importance of pollinators and decide to honor them also. After all, flowers would not exist without pollinators.

Some flowers accept a variety of pollinators, for instance, black eyed Susan (Maryland’s state flower) and goldenrod (state flower of Kentucky, Nebraska and South Carolina). Others are more selective, such as the flowering dogwood (state flower of North Carolina and Virginia). A few are extremely specialized like the yucca (state flower of New Mexico), which needs a tiny moth. No one else can do the job. Still others require unusual pollinators like the saguaro (state flower of Arizona) whose main pollinators are bats, or columbines (state flower of Colorado) which are pollinated by hummingbirds.

Curiously, thirteen states have chosen official state flowers that are not native and therefore not truly representative of the state. Fortunately seven of them decided to add an official state wildflower, for instance, the state flower of Ohio is the carnation and its wildflower is the white trillium. I will mention a few of them because they contribute something valuable to this tale of pollination. In other cases, I will refer to the state tree if it bears flowers that add something to the pollination story.

One may wonder why some states chose flowers native to the old world rather than those that represent the state flora. It seems that state flowers were chosen more for their beauty, or economic importance. Perhaps part of the explanation is that this is such a nation of immigrants that many people are more familiar with the rose or the carnation than with any local flowers. Economic importance counts too. Thus, it comes as no surprise that Florida chose the orange blossom as a state flower.

In a few cases there is some confusion about the choice of state flower. This is not surprising considering that legislators are not botanists. The common name could include only one or several species of similar plants. Which one of several violets is the state symbol? Those states that chose the rose, were they thinking of a native species of rose, or one of the common cultivated varieties? Different sources give slightly different interpretations to these choices. In general, I will follow the scientific nomenclature used by the United States National Arboretum, but I may include other interpretations in some instances if they illustrate an interesting pollination point.

Here is the story of pollination and pollinators as told through the examples of official state flowers. In the next post I will describe the kind of pollination that took place long before there were any insects or other animals to do the job, in fact, long before there were flowers. Then, I will examine the earliest forms of insect pollination. In following posts I will cover an assortment of floral strategies, from the ones that attract hordes of different pollinators to the specialists that prefer to deal with a select number of helpers or even just one. I will include some strategies that include nasty tricks played on pollinators and also an intriguing phenomenon, toxic nectar. It makes one wonder why a flower would want to make its pollinators sick. I haven’t forgotten pollinators of a different kind, non-insect ones, birds and bats. Finally, to wrap up this tale, I will take a look at state flowers and pollinators of economic importance.

State Symbols, USA
Dowden, Anne O. State Flower. 1978
Cooper, Jason, The Rourke Guide to State Symbols. Flowers. 1942

Friday, November 21, 2014

My Metallic Green Bees

My favorite bee, Augochlora,
on cone flower.
© Beatriz Moisset

I often marvel at the exquisitely colored bees that visit my flowers. My favorite ones have a metallic green sheen that makes me think of them as miniature robots. How do they get such an interesting hue? Many other insects, such as wasps, flies, butterflies and beetles, also dress up on shiny armors. Metallic colors range from blue to copper and even red, with green being perhaps the most common. I decided to learn more about these shimmering hues, so different from ordinary colorations.

Another view of my favorite bee, the pure golden-green bee (Augochlora pura)
© Beatriz Moisset
It turns out that biologists have a lot to learn about this subject. The physics is quite complicated and I will not attempt to give more than the simplest explanation here. Most colors we see in nature are produced by pigments. The shiny and iridescent effects we see on certain animals are caused, not by pigments, but by tiny structures in the cuticle (the skin) of insects and thus they are called structural colors. Those microscopic ridges or plates or cross ribs make the light rays bounce off, scattering them in ways that produce special effects. The term iridescence lumps together three different types of chromatic effects: metallic looks, spectral iridescence (rainbow effects) and opal-like effects. Peacock feathers and Morpho butterfly wings are fine examples of iridescence. Some metallic colors observed in insects show a certain degree of iridescence. They change from green to copper or red depending on the angle of the light rays.

Parasitic wasp, Perilampidae.
© Beatriz Moisset
Pigments tend to decay after death, so ordinary tints usually fade away. Museum collections of dead specimens may look rather boring. In contrast, structural colors remain vibrant for a long time because the miniature structures don't change as long as the cuticle is intact. They may even be present in fossils.

Green-bottle blowfly, Lucilia.
© Beatriz Moisset
Let us get back to metallic colors, what function do they serve? Why do so many different insects wear these shimmering hard-looking coats? Some biologists think that structural colors serve functions of camouflage, signaling or disguise. What do these words mean? Can we find examples of these functions?

"Camouflage" enables the insect to blend with its surroundings and escape notice by predators. Let us look at my shiny bee. It blends moderately well with the foliage on which it often rests despite the fact that it is not a perfect imitation. It turns out that, while plants make green pigment in abundance, insects have trouble producing such pigment. The best approximation to the appearance of leaves is a structural color.

"Signaling" refers to sending a sign or a coded message to others. It may be a warning to predators, such as: I am poisonous; you don't want to eat me. It may be a message to other males of the same species: I am stronger, I am brighter; you'd better give up. Or, it may be telling females: I am the best male around.

Dogbane beetle.
© Beatriz Moisset
Finally "disguise" is a little different from camouflage. It is an imitation or mimicry of something else. The purpose is to deceive the observer

I hope you enjoy this gallery of metallic insects. It includes bees, wasps, flies, beetles and a butterfly. You may recognize some of these beauties in your garden or notice other ones.

Augochloropsis, a relative of Augochlora. © Beatriz Moisset

Parasitic wasp, Torymus. © Beatriz Moisset
Cuckoo wasp. Chrisididae. © Beatriz Moisset
Longlegged fly, Dolichopodidae. © Beatriz Moisset
Syrphid fly, Copestylum. © Beatriz Moisset
Tiger beetle. Cicindelidae. © Beatriz Moisset
Buprestid beetle. © Beatriz Moisset
Mating dogbane beetles. © Beatriz Moisset
Red spotted purple butterfly. © Beatriz Moisset

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© Beatriz Moisset. 2014 

Tuesday, November 18, 2014

Crab spiders hiding in goldenrod

Crab spider (Mecaphesa) on goldenrod. © Beatriz Moisset
Crab spiders are good at hiding among the flowers. Even after I annoyed this one quite a bit, it still remained somewhat hidden.

The same spider coming out of hiding. © 2007 Beatriz Moisset
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© Beatriz Moisset. 2014

Monday, November 3, 2014

Sticky Pollen

Arrowwood (Viburnum dentatum) in bloom. © Beatriz Moisset
 Some kinds of pollen are stickier than others. I marvel at that of arrowwood, Viburnum dentatum. These flowers attract numerous insects. The pollen coating can be impressive. It is hard to identify some of the bees when their features are hidden by abundant white dust.

Can you tell which kind of bee? © Beatriz Moisset
Probably the same bee. Hard to tell. © Beatriz Moisset
A closeup of another bee. © Beatriz Moisset
And one more. Take a look at those anthers. © Beatriz Moisset
Flower longhorn beetle taking a break. © Beatriz Moisset
Even the lady beetle larva gets coated with pollen. © Beatriz Moisset

Monday, October 20, 2014

Blowflies are Pollinators Too

Mating Lucilia flies. © Beatriz Moisset

A bright metallic green insect lands on one of the flowers in your garden. It has large red eyes. Aside from the interesting colors, it looks like a plump house fly. You can't decide whether you like it or not. Its scientific name is Lucilia, its common one is greenbottle blowfly. It is unusual for a scientific name to be prettier than the common name. You dislike the common name even more when you find out its meaning. According to the Free Dictionary a blowfly is "any of several flies of the family Calliphoridae that deposit their eggs in carcasses or carrion or in open sores and wounds." Carrion? Open sores? Definitely not pretty.

Lucilia on common milkweed. © Beatriz Moisset

So, it is agreed, Lucilia is an ugly fly despite its startling colors. But, does it have some redeeming features? Fortunately, it does. Its habits are put to full advantage in forensics. By examining the Lucilia's maggots found in a corpse it is possible to determine the time of death. Another use is in medicine. This may cause you some revulsion, but it isn't as bad as it seems. Open wounds that don't heal and begin to accumulate dead tissue can be cleaned up by blowfly larvae. Let me clarify that only maggots raised in perfectly sterile conditions are used for this purpose. The larvae feed only on the dead cells and leave the healthy tissue untouched. This method is superior to that of the most expert scalpel held by a surgeon.

© Beatriz Moisset

But this is a blog about pollinators, so let us get into this subject. Blowflies, Lucilia in particular, are good pollinators of certain flowers. You see them frequently visiting a variety of blooms in your garden. They are more efficient than bees in pollinating onions and cabbages. I wonder why they show such preference for plants so notorious for their strong odor. Perhaps there is a connection between these plants' fragrance and that of smelly dead things fowever I haven't found any references so far. Most pollinators don't fair well in greenhouses. Lucilia, on the other hand, is easy to raise and to maintain in these conditions, so this is the preferred pollinator of the mentioned plants.

Two Lucilia flies pollinating Allium. © Beatriz Moisset

In summary, blowflies aren't that bad at all. In fact, they are so beneficial that we may begin to see their beauty. Let us welcome them in our gardens.
Lucilia on mountain mint. © Beatriz Moisset

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Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014