Sunday, February 7, 2016
Friday, February 5, 2016
|Big Eared Townsend Fleddermouse.PD-USGov, exact author unknown|
Who would think of putting a dollar value on a bat? Well, it turns out that some researchers have done just that. I am not talking about a baseball bat but about that creature of the night so loathed by some. We tend to associate bats with witches and demons rather than with crops.Is there a reason for putting an economic value on a bat? The answer is: Yes. Bats feed on flying insects at night. Many of those insects are pests that damage our valuable crops. So it turns out that bats are valuable to farmers.
A group of scientists have been trying to estimate the numbers of insects bats eat and the possible impact on agriculture and forestry if bats stopped supplying this pest control. They published their conclusions in the scientific journal, Science. Through a number of complex calculations of pesticide application and crop losses they came up with a range between $3.7 billion and $53 billion a year in the United States alone. It is not possible to be more precise when considering so many variables. Anyway the numbers are impressive.
It is worth mentioning that these maligned creatures have other functions in addition to the pest control discussed in this study. They are pollinators of many night blooming flowers. Cacti, in particular, are dependent on bats for pollination. Many cacti of the West synchronize their blooming time with the migration of some species of bats. Try to imagine what the West would be like without cacti.
|Bat pollinating Agave desmettiana. © Carlos Machado|
Another service, especially in the tropics is seed dispersal. Bats eat the fruits of many trees, such as fig trees and pass the seeds far from the mother trees. It would be impossible to put a monetary value on this function, but it is becoming apparent that bats are essential to reforestation in tropical regions.
Unfortunately, in recent times, bats are encountering serious problems. There is one disease in particular that is decimating the populations of bats in the United States. This fungal disease, called "white nose syndrome", weakens and kills large number of bats, especially during the winter. It is for this reason that the researchers decided to investigate how the loss of bats would affect agriculture. Even lacking more accurate numbers the results are alarming; the losses to crops and forestry could be very serious.
It is only recently that a cure for white nose syndrome has been found. A bacteria attacks the fungus that causes this illness. Infecting bats with this bacteria cures them from the illness. Steps are taken to restore the health of bat populations. It is still a long road to complete success and reports of the illness spreading to other caves and to other regions continue. Cautious optimism is in order.
The web of life is intricate and often we don’t know enough about all the threads that make this tapestry. This is another example of a creature whose value we fail to recognize. It took a threat to the welfare of bats, such as the white nose syndrome for the world to stand up and take notice. We are only now beginning to appreciate the value of the free services provided by these creatures: pollination, seed dispersal and pest control. We have to look at bats with renewed respect. Let us develop a kinder attitude towards our friends, the bats.
|Bat house © Robert Lawton|
White nose syndrome cure
Seed dispersal by bats
Sunday, June 28, 2015
Thursday, June 25, 2015
Pollen is a valuable commodity. The less pollen needed, the more energy is left for other functions. Flowers resort to several strategies to economize on pollen. Some use a method called explosive pollination, others resort to buzz pollination. Both methods are well illustrated by official state flowers.
|Mountain laurel in bloom. © Beatriz Moisset|
Explosive Pollination of Mountain Laurels
Mountain laurel (Kalmia latifolia), Pennsylvania’s and Connecticut's state flower, has a singular way to ensure that its insect visitors carry pollen to other flowers of its species. The unopened blossoms present little knobs which give them a funny look. Their function becomes apparent when the flower opens. They are pockets that hold the anthers trapped. Anthers are the part of the flower that produces male cells, pollen.
|Mountain laurel flower before an insect's visit. © Beatriz Moisset|
|Flower tripped by an insect. © Beatriz Moisset|
In most flowers the anthers are free and exposed to spread their pollen at the slightest touch of a flower visitor. The mountain laurel has a different strategy. The pollen is well protected against rain and wind; but, when a pollinator lands on the flower searching for nectar, the weight acts as a trigger, causing the taut stem of the anther to spring. The anther hits the pollinator gently on the back and gives it a dusting of pollen.
This method allows mountain laurel flowers to produce only a moderate amount of pollen because most of it ends up where it is intended, on the body of a pollinator, rather than being wasted in other ways.
Connecticut: Mountain laurel
Pennsylvania: Mountain laurel
Explosive Pollination of Pea-like Flowers
|Texas Bluebonnet. Wikicommons © Jacopo Werther|
When a pollinator lands on a blossom, its weight triggers a mechanism causing the keel to spread open and the anthers and stigma jump up out of the enclosure. This is called tripping. The insect has to be heavy enough to cause such reaction. Some bumble bees are pros at this task; honey bees, on the other hand, dislike being pounced upon. After a few times, they learn to sneak around and steal the nectar through a small opening at the base of the keel. Only novices perform pollination. Once they learn this trick no more pollen is transferred to the stigmas. Nevertheless managed honey bees are widely used to pollinate alfalfa and clover. Bee hives provide a large labor force that makes up for this deficiency. Some bumble bees, especially the short-tongued species, are also inclined to a little larceny. However, they are generally considered highly competent pollinators of alfalfa and clover.
|Clover, another papilionoid flower. © Beatriz Moisset|
Vermont: Red Clover
Buzz Pollination or the Salt Shaker Technique
Other flowers make the pollinators work for pollen in a different way. Interestingly enough, honey bees never learned how to do the job I will describe, but native bumble bees and numerous species of bees are real pros.
In most flowers
the pollen is made available to pollinators as soon as it is ripe.
The anther splits open. We all have seen the golden dust many flowers
have. If we touch it, it sticks to our fingers. Rhododendrons and
azaleas do something else. They keep the pollen enclosed inside the
anther. It can only come out through a small opening at the tip.
Several other native flowers, like tomato and blueberry have a
|Azalea Andrena bee pollinating azalea. Observe the pores at the tips of the anthers. © Beatriz Moisset|
In order to extract it, the bee has to cling to the anther and give it a good shake. It accomplishes this by vibrating its flight muscles while keeping the wings still; it is like running the car engine in neutral. Pollen comes in clouds and clings to the body of the pollinator. Later, the bee proceeds to package its loot in the little baskets of the hind legs.
|Buzz pollination of azalea. Video. © Beatriz Moisset|
Two states have official flowers that exemplify this method of pollination, Washington has chosen the Coast Rhododendron (Rhododendron macrophyllum) and West Virginia has another species of Rhododendron (Rhododendron maximum). Georgia’s official wildflower, azalea (Rhododendron prunifolium), follows the same system of pollination; its official flower is the rose; but, fortunately, they decided to honor a native plant in addition to a non-native flower.
Georgia (official wildflower): Azalea
Washington: Coast Rhododendron
West Virginia: Rhododendron
Other plants select their pollinator clientele through other methods. Some hide the nectar rather than the pollen. A different set of skills are needed to deal with these flowers as we'll see in the next post.
Thursday, June 18, 2015
Friday, May 22, 2015
Most flowers want to make it easy for the visitor to find its way around. Thus, in addition to attracting pollinators with their colors and aromas, they guide their visitors in the right direction. This serves two purposes; it facilitates the task of the pollinator and enables the flower to have its pollen deposited where it is most needed.
Have you noticed the streaks of color radiating from the center of many blossoms? These are the nectar guides that tell the visitor: this is the way to the food. Violets and lupines are good examples. The variety of violets is amazing. We can count more than a hundred species and hybrids. Most of them are native, although a few have been introduced from Europe. As a footnote, it is worth mentioning that some violet species are the food plant of fritillary butterflies.
|© Beatriz Moisset|
Don’t you find it rather surprising that the humble violet is the state flower of four states? It would be more correct to say violets, plural. Illinois did not attempt to specify which species, even after giving their flower the name of purple violet to distinguish it from yellow violets. New Jersey and Wisconsin chose the Viola sororia and Rhode Island, Viola palmata. Botanists and horticulturists pay attention to these things. However, legislators often ignore such details. This doesn't matter since all violets exemplify the nectar guides vividly.
Illinois: Purple Violet (Viola)
New Jersey: Common Blue Violet (Viola sororia)
Rhode Island: Violet (Viola palmata)
Wisconsin: Common Blue Violet (Viola sororia)
|Texas bluebonnet © Jacopo Werther. Wikicommons|
A slightly different type of nectar guides is present in bluebonnets (Lupinus). This Texas state flower includes all the species of bluebonnet that grow in that state. The guides become visible only when the flower opens and becomes receptive to pollinators. Bluebonnets belong to the pea family, Fabaceae, which is valuable to ecosystems because it enriches the soil by fixing nitrogen.
Texas: Texas Bluebonnet (Lupinus spp.)
Some flowers use a different way to guide the pollinator to the desired place. It is called bull's eye. The color of the flower's center contrasts with the rest of the blossom. Several state flowers illustrate variations of this theme. Maryland's black-eyed Susan and Oklahoma's Indian blanket are fine examples. So are Florida's tickseed and Kansas' sunflower.
|Sunflower © Beatriz Moisset|
Pollination researchers played a trick on visitors to these flowers to test the hypothesis that the bull's eye helped them find their way. They methodically pulled out all the petals of flowers of this type and glued them back in after reversing their position so that the darker part was in the outside. True enough, bees would land on the blossom, walk to the edge and stick their tongues out in search of nectar. They must have been mighty puzzled and annoyed at finding none.
Some flowers, such as coreopsis, apparently lack this contrast. They appear uniformly yellow to our eyes. But bees see certain colors that escape us. They can see in the range of ultraviolet light, the so-called black light. The flowers, in turn, have a pattern that becomes visible only under this particular kind of light waves. The flower that appears uniformly yellow to us is seen by a bee as having a black center surrounded by a light halo.
Maryland, Florida and Kansas have state flowers with bull's eyes, black-eyed Susan, tickseed, and sunflower, respectively. Oklahoma is rather unusual in having not one but three types of flower symbols: the mistletoe as its floral emblem, the Oklahoma rose as its state flower and the Indian blanket, as its state wildflower. The latter has a conspicuous bull's eye.
Maryland: Black-eyed Susan (Rudbeckia hirta)
Florida (Wildflower): Tickseed (Coreopsis)
Kansas: Sunflower (Helianthus annuus)
Oklahoma (Wildflower): Indian Blanket (Gaillardia pulchella)
This article is about one of the many ways in which flowers increase the efficiency of the pollination process. In the next post we'll see examples of another strategy, frugality.
Black-eyedSusan under ultraviolet light
Dowden, Anne O. State Flowers. 1978
Cooper, Jason, The Rourke Guide to State Symbols. Flowers. 1942
Wednesday, March 18, 2015
|Some of the many visitors to goldenrod. © Beatriz Moisset
|Monarch butterfly on goldenrod. © Beatriz Moisset|
|Metallic green bee. © Beatriz Moisset|
Two states, Kentucky and Nebraska, have the goldenrod as their state flower. It is not clear which species of goldenrod Kentucky picked, but it is likely the Canada goldenrod (Solidago altissima). Nebraska’s choice is clearer, the giant goldenrod (Solidago gigantea). South Carolina, not satisfied with a state flower, also has a state wildflower. It is the Canada goldenrod. It is worth mentioning that Delaware has a state herb, the anise-scented or sweet goldenrod (Solidago odora).
Two other state flowers also have mass appeal. Like goldenrod, they are members of the daisy or aster family, easy to access by different kinds of visitors. They are Kansas’ sunflower (Helianthus annuus) and Maryland’s Black-eyed Susan (Rudbeckia hirta). It is worth mentioning here that two states, Florida and Mississippi, chose the tickseed (Coreopsis spp.) as a state wildflower in addition to their official state flowers, the orange blossom and the magnolia, respectively.
|Bumble bee on sunflower. © Beatriz Moisset|
|Coreopsis. © Beatriz Moisset|
South Carolina (wildflower): Goldenrod
Delaware (herb): Goldenrod
Maryland: Black-eyed Susan
Florida (wildflower): Coreopsis
Mississippi (wildflower): Coreopsis
The indiscriminate pollination strategy represented by all these flowers has advantages and also disadvantages. They suffer no shortage of pollinators. If one species is doing poorly one year, as it often happens in the insect world, there are plenty more to fill in the deficiency. However, sometimes too much of a good thing can be bad. Some of these non-specialized pollinators may be visiting a variety of flowers instead of being faithful to just one species so they end up carrying the wrong kind of pollen in such cases.
Blossoms with such mass appeal give me the opportunity to introduce the reader to the main groups of pollinators. They are all well represented on these mass appeal flowers.
|Andrenidae bee © Beatriz Moisset|
|Bumble bee. © Beatriz Moisset|
|Wasp. © Beatriz Moisset|
|Syrphid fly. © Beatriz Moisset|
|Syrphid fly. © Beatriz Moisset|
|Yellow collared scape moth on goldenrod. © Beatriz Moisset|
|Soldier beetle on goldenrod. © Beatriz Moisset|
In the following chapters we’ll see flowers that have chosen a different strategy. They are pickier or more selective. Some attract a handful of visitors; a few go to the extreme of having relationships with only one species of pollinators.
Canada goldenrod visitors in IL. http://eol.org/data_objects/31873000