Friday, May 22, 2015

This Way to the Restaurant.

Nectar guides © Beatriz Moisset
Nectar Guides

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.)

Bull’s Eye

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.

Indian blanket. © Beatriz Moisset 

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.

Coreopsis. The bull's eye is visible only under ultraviolet light. © Beatriz Moisset 
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

Mass Appeal and Pollination

Some of the many visitors to goldenrod.  © Beatriz Moisset

Many flowers are not particularly selective; they welcome all kinds of visitors. They are wide open, easily accessible, thus many insects can reach the nectar and/or pollen regardless of whether their tongues are long or short. Such flowers provide a convenient standing platform to save their visitors the inconvenience of hovering over them. Their structure is simple so the pollinators don’t need to figure out how to open them in order to reach their rewards. Goldenrod is a fine example.
Monarch butterfly on goldenrod. © Beatriz Moisset
 I have spent countless happy hours observing goldenrods and photographing their numerous visitors. The one most common in my area is the Canada goldenrod. Several hundreds of species visit their flowers. Bear in mind that not all flower visitors qualify as pollinators. Some are not efficient at carrying pollen, or sit in one place for a long time and never make it to another plant. Such is the case of ambush bugs, whose only concern is to snare hapless pollinators to make a meal out of them. If you are interested on photographing and identifying pollinators this is a good place to start.

Metallic green bee. © Beatriz Moisset
 This plant blooms in the fall. It often gets blamed for allergies, but the real culprit is another plant that grows close by, sometimes intermingled with goldenrods, ragweed. Its flowers are inconspicuous because its pollen gets carried by the wind, not by officious pollinators. This is how it gets into our nostrils and causes our suffering. The much maligned goldenrods have larger, heavier and stickier grains of pollen that cannot get airborne and that require help from visitors.

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).

Bumble bee on sunflower. © Beatriz Moisset

Coreopsis. © Beatriz Moisset
 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.

Kentucky: Goldenrod
Nebraska: Goldenrod
South Carolina (wildflower): Goldenrod
Delaware (herb): Goldenrod
Kansas: Sunflower
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
 Let us start by getting acquainted with bees. More than 80 species have been seen on goldenrods. Some of them deserve mention. Bumble bees are larger than other bees, plump, dark with yellow or white stripes, and hairy. Metallic green bees are small and gorgeously colored. They may escape notice if one isn’t very observant; but it is easy to become captivated by their shiny aspect. Mason bees and leaf-cutting bees carry pollen on their underbelly, unlike most other bees that carry it on their hind legs. Most of them are dark, nearly black and about the size of honey bees or slightly smaller.

Wasp. © Beatriz Moisset
 Wasps are related to bees and sometimes people confuse them. Most wasps are less hairy than bees and have narrow waists. They raise their young on a diet of insects or spiders, instead of pollen and nectar as bees do. Adult wasps need nectar to fuel their flight. Thus, they are frequent flower visitors and accomplish some pollination.

Syrphid fly. © Beatriz Moisset
Syrphid fly. © Beatriz Moisset

Many types of flies, including mosquitoes and gnats visit flowers to feed on their nectar. Some are good pollinators. The Syrphid flies, also called flower flies, are among the most assiduous flower visitors. Most of them mimic bees or wasps and are frequently mistaken for them. However, they don’t sting and there is no reason to fear them.

Buckeye butterfly on goldenrod. © Beatriz Moisset
Pyrausta moth on sunflower. © Beatriz Moisset
Yellow collared scape moth on goldenrod. © Beatriz Moisset
 Butterflies, skippers and moths have extremely long tongues that they can use like drinking straws when sipping nectar. They favor long necked flowers and carry pollen from one to another.

Polished lady beetle on sunflower. © Beatriz Moisset
Soldier beetle on goldenrod. © Beatriz Moisset
Finally, beetles, although not well specialized for pollination, are also capable of doing so in special circumstances. We already mentioned magnolia pollination by beetles. They also visit other flowers and can do a reasonably good job in some cases.

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.

Monday, March 2, 2015

The Earliest Pollinators: Beetles and Flies

Magnolia © Beatriz Moisset
 By the time the first flowering plants appeared on Earth there weren’t any bees or butterflies. Those superb pollinators would take millions of years to evolve from wasps and moths respectively. So, who would be attracted to flowers? Who would carry pollen?

Other insects, although not adapted to sipping nectar and storing pollen in little baskets, liked to visit flowering plants to eat the pollen. Sometimes, they also devoured the flowers themselves. Beetles and flies were among the earliest pollinators. These two groups of insects visit the flowers of magnolia and water lilies to this day. In general, flowers pollinated by beetles are cup-shaped to allow these insects to stay for some time. They are strongly scented by fruity or rotten smell. The petals may be tough and leathery, helping them to put up with the abuse; many of them are greenish or creamy white.

Tumbling flower beetles on magnolia © Beatriz Moisset
The state flower of Louisiana and of Mississippi is the Magnolia (Magnolia grandiflora) which is an example of some of the oldest flowering plants; it presents all the qualities listed above and it is pollinated by beetles that use the flowers as a singles bar. They stay for hours eating, drinking, mating and making a mess of the place. When they arrive, usually only the female part of the flower is mature enough, so if they carry pollen from other flowers they get cross-pollinated, but by the time the beetles leave, the stamens or male parts have become ripe. The visitors get easily dusted with it and ready to carry it to the next awaiting singles bar. Beetles and flies find a coating of nectar covering the petals that they can slurp as they go along.

Dance fly on Magnolia © Beatriz Moisset

It is worth mentioning here the tulip tree (Liriodendron tulipifera) because it is the state tree of Indiana, Kentucky and Tennessee. The state flowers of Indiana and Tennessee are not native; they are the peony and iris, respectively, so I like to think of the tulip tree blossom as the honorary state flower of these two states. The tulip tree is a relative of magnolias, equally ancient; its flower bears some resemblance to magnolias. It is also pollinated by beetles, although bees and other insects also contribute to its pollination.

Another ancient flower, the California poppy (Eschscholzia californica), California’s state flower is also pollinated by beetles in some instances. These are more numerous than bees in arid areas. Several species of bees, including honey bees also pollinate these flowers.

California poppy © Audrey. Flickr
State flowers that illustrate the earliest pollinators:
Louisiana: Magnolia
Mississippi: Magnolia
California: California Poppy

Once plants came up with this novel solution to their fertilization process, there was no stopping them. Evolution accelerated and an ever growing variety of flowering plants emerged from the older lineages. In turn, more insects evolved to take advantage of this resource. This is how some carnivorous wasps went vegetarian. They became what we now know as bees. Pollen and nectar supplied all their needs.

Also some moths developed a taste for nectar during their adult life. Unlike most moths, they were diurnal and often sported fancy colors. In other words, they evolved into butterflies. Being frequent flower visitors they became pollinators. This is not to say that wasps and moths, the predecessors of bees and butterflies don’t pollinate. In fact some of them are valuable and are highly specialized ones.

The following posts deal with these pollinators and their flowers.  We will start with the ones who invite a wide assortment of guests. They have mass appeal and several state flowers illustrate this nicely.

Pollinators of Official State Flowers 
Mass Appeal and Pollination

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 seeds.

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.

Also see: Pollinators of Official 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.

More on pollinators and state flowers
State Symbols, USA
Dowden, Anne O. State Flowers. 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
© Beatriz Moisset

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© Beatriz Moisset. 2014