Why Are Some Plants Overcompensating?

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Gardeners are all too familiar with herbivory. Countless times I have been awaiting a bloom to burst only to have the buds nipped off the night before they opened. While this can be devastating for many plant species (not to mention my sanity), for certain plant species, an encounter with a hungry herbivore may actually lead to an increase in reproductive fitness.

Overcompensation theory is the idea that, under certain conditions, plants can respond to herbivore damage by producing more shoots, flowers, and seeds. It goes without saying that when this idea was originally proposed in the late 80's, it was met with its fair share of skepticism. Why would a plant capable of producing more shoots and flowers wait to be damaged to do so? The answer may lie in in the realm of biological trade-offs.

Overcompensation may evolve in lineages that tend to grow in habitats where there is a "predictable" amount of herbivory in any given growing season, perhaps a region where large herbivores migrate through annually. Plants in these habitats may conserve dormant growing tips and valuable resources to be used once herbivory has occurred. Perhaps this also serves as a cue to upregulate antiherbivory compounds in new tissues. The trade-off is that the plants incur a cost in the form of fewer flowers and thus reduced reproduction when herbivory is low or absent.

Scarlet gilia ( Ipomopsis aggregata )

Scarlet gilia (Ipomopsis aggregata)

It could also be that plants are exhibiting two different strategies - one to deal with competition and one to deal with herbivory. If herbivory is low, plants may become more competitive, thus favoring rapid vertical growth of one or a couple shoots. When herbivory is high, rapid vertical growth becomes disadventageous and overcompensatory branching and flowering can provide the higher fitness benefits.

These possibilities are not mutually exclusive. In fact, since the late 80's, experts now believe that overcompensation is not an "either/or" phenomenon but rather a spectrum of possibilities that are dictated by the conditions in which the plants are growing. Certainly overcompensation exists but which conditions favor it and which do not?

Research on scarlet gilia (Ipomopsis aggregata), a biennial native to western North America, suggests that overcompensation comes into play only when environmental conditions are most favorable. Soil nutrients seem to play a role in how well a plant can bounce back following herbivore damage. When resources are high, the results can be quite astounding. Early work on this species showed that under proper conditions, plants that were browsed by upwards of 95% produced 2.4 times as much seed as uneaten control plants. What's more, the resulting seedlings were twice as likely to survive than their uneaten counterparts.

Things change for scarlet gilia growing in poor conditions. Low resource availability appears to place limits on how much any given plant may respond to browsing. Also, herbivory can really hamper flowering time. Because scarlet gilia is pollen limited, anything that can cause a disruption in pollinator visits can have serious consequences for seed set. In at least one study, browsed plants flowered later and received fewer pollinator visits as a result.

More recent work has been able to add more nuance to the overcompensation story. For instance, experiments done on two subspecies of field gentian (Gentianella campestris), add further support to the idea that overcompensation is a matter of trade-offs. They showed that, whereas competition with neighboring plants alone could not explain the benefits of overcompensation, browsing certainly can.

Field gentian ( Gentianella campestris )

Field gentian (Gentianella campestris)

Plants growing in environments where herbivory was higher overcompensated by producing more branching, more flowers, and thus more seed, all despite soil nutrients. It appears that herbivory is the strongest predictor of overcompensation for this gentian. What's more, when these data were fed into population models, only the plants that responded to herbivory by overcompensation were predicted to show any sort of population growth in the long term.

Despite all of the interest overcompensation has recieved in the botanical literature, we are only just beginning to understand the biological mechanisms that make it possible. For starters, we know that when a dominant shoot or stem gets damaged or removed, it causes a reduction in the amount of the plant hormone auxin being produced. When auxin is removed, tiny auxiliary buds at the base of the plant are able to break dormancy and begin growing.

Removal of the dominant shoot or stem can also have major impact on the number of chromosomes present in regrowing tissues. Work on Arabidopsis thaliana revealed that when the apical meristem (main growing tip of a vertical stem) was removed, the plant underwent a process called "endoreduplication" in which the cells of the growing tissues actually duplicate their entire genome without undergoing mitosis.

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Endoreduplication is a complex process with lots of biological significance but in plants it is often associated with stress responses. By duplicating the genomes of these new cells, the plants may be able to adjust more rapidly to their environment. This often manifests in changes to leaf size and shape and an uptick in plant defenses. Thus, plants may be able to fine tune the development of new tissues to overcompensate for browsing. Certainly far more work is needed to understand these mechanisms and their functions in more detail.

Overcompensation is not universal. Nonetheless, it is expected to occur in certain plants, especially those with short life cycles, and under certain environmental conditions, mainly when herbivore pressure and nutrient availability are relatively high. That being said, we still have plenty more to learn about this spectrum of strategies. When does it occur and when does it not? How common is it? What are the biological underpinnings of plants capable of overcompensation? Are some lineages more prone to overcompensation than others? Only more research can say for sure!

Photo Credits: [1] [2] [3] [4] [5]

Further Reading: [1] [2] [3] [4]

 

 

Fossils Shine Light On the History of Gall-Making Wasps

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We can learn a lot about life on Earth from the fossil record. I am always amazed by the degree of scrutiny involved in collecting data from these preserved remains. Take, for instance, the case of gall-making wasp fossils found in western North America. A small collection of fossilized oak leaves is giving researchers insights into the evolutionary history of oaks and the gall-making wasps they host.

Oaks interact with a bewildering array of insects. Many of these are gall-making wasps in the family Cynipidae. Dozens of different wasp species can be found on a single oak tree. Female wasps lay their eggs inside developing oak tissues and the larvae release hormones and other chemicals that cause galls to form. Galls are essentially edible nursery chambers. Other than their bizarre shapes and colors, the compounds released by the wasp larvae reduce the chemical defenses of the oak and increase the relative nutrition of the tissues themselves. Often, these relationships are precise, with specific wasp species preferring specific oak species. But when did these relationships arise? Why are oaks so popular? What can fossil evidence tell us about this incredible relationship?

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Though scant, the little fossil evidence of oak galls can tell us a lot. For starters, we know that gall-making wasps whose larvae produce structures similar to that of the Cynipids have been around since at least the late Cretaceous, some 100 million years ago. However, it is hard to say for sure exactly who made these galls and exactly what taxonomic affinity the host plant belongs to. More conclusive Cynipid gall fossils appear again in the Eocene and continue to pop up in the fossil record throughout the Oligocene and well into the Miocene (33 - 23 million years ago).

Miocene aged fossils are where things get a little bit more conclusive. Fossil beds located in the western United States have turned up fossilized oak leaves complete with Cynipid galls. The similarity of these galls to those of some present day species is incredible. It demonstrates that these relationships arose early on and have continued to diversify ever since. What's more, thanks to the degree of preservation in these fossil beds, researchers are able to make some greater conclusions about why gall-making wasps and oaks seem to be so intertwined.

Holotype of Antronoides cyanomontanus galls on fossilized leaves of  Quercus simulata . 1) Impression of the abaxial surface of the leaf, showing the galls extending into the matrix. 2) Galls showing close association with secondary veins. 3) Gall showing the impression of rim-like base partially straddling the secondary vein. 4) Close-up of gall attached at margin extending down into the matrix. 5) Gall uncovered revealing spindle-shaped morphology.

Holotype of Antronoides cyanomontanus galls on fossilized leaves of Quercus simulata. 1) Impression of the abaxial surface of the leaf, showing the galls extending into the matrix. 2) Galls showing close association with secondary veins. 3) Gall showing the impression of rim-like base partially straddling the secondary vein. 4) Close-up of gall attached at margin extending down into the matrix. 5) Gall uncovered revealing spindle-shaped morphology.

1)  Xanthoteras clavuloides  galls on fossilized  Quercus lobata , showing gall attached to secondary vein. Specimen in California Academy of Sciences Entomology collection, San Francisco. 2) Two galls of attached to a secondary vein showing overlap of their bases. Specimen in California Academy of Sciences Entomology Collection, San Francisco. 3) Three galls collected from leaf of California  Quercus lobata  showing clavate shape and expanded, ring-like base. 4) Gall showing the annulate or ribbed aspect of the base, which is similar to bases of  Antronoides cyanomontanus  and  A. polygonalis . 5) Galls showing clavate shape, pilose and nonpilose surfaces, and bases.

1) Xanthoteras clavuloides galls on fossilized Quercus lobata, showing gall attached to secondary vein. Specimen in California Academy of Sciences Entomology collection, San Francisco. 2) Two galls of attached to a secondary vein showing overlap of their bases. Specimen in California Academy of Sciences Entomology Collection, San Francisco. 3) Three galls collected from leaf of California Quercus lobata showing clavate shape and expanded, ring-like base. 4) Gall showing the annulate or ribbed aspect of the base, which is similar to bases of Antronoides cyanomontanus and A. polygonalis. 5) Galls showing clavate shape, pilose and nonpilose surfaces, and bases.

Gall-making wasps seem to diversify at a much faster rate in xeric climates. The fossil records during this time show that mesic tree speciess were gradually being replaced by more xeric species like oaks. Wasps seem to prefer these drier environments and the thought is that such preferences have to do with disease and parasite loads.

Again, galls a large collections of nutrient-rich tissues that are low in defense compounds. Coupled with the juicy grub at their center, it stands to reason that galls make excellent sites of infection for fungi and other parasites. By living in drier habitats, it is believed that gall-making wasps are able to escape these environmental pressures that would otherwise plague them in wetter habitats. The fossil evidence appears to support this hypothesis and today we see similar patterns. White oaks are especially drought tolerant and its this group of oaks that host the highest diversity of gall-making wasps.

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2] [3]

Toxic Nectar

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I was introduced to the concept of toxic nectar thanks to a species of shrub quite familiar to anyone who has spent time in the Appalachian Mountains. Locals will tell you to never place honeybee hives near a patch of rosebay (Rhododendron maximum) for fear of so-called "mad honey." Needless to say, the concept intrigued me.

A quick internet search revealed that this is not a new phenomenon either. Humans have known about toxic nectar for thousands of years. In fact, honey made from feeding bees on species like Rhododendron luteum and R. ponticum has been used more than once during times of war. Hives containing toxic honey would be placed along known routs of Roman soldiers and, after consuming the seemingly innocuous treat, the soldiers would collapse into a stupor only to be slaughtered by armies lying in wait.

Rhododendron luteum

Rhododendron luteum

The presence of toxic nectar seems quite confusing. The primary function of nectar is to serve as a reward for pollinators after all. Why on Earth would a plant pump potentially harmful substances into its flowers?

It is worth mentioning at this point that the Rhododendrons aren't alone. A multitude of plant species produce toxic nectar. The chemicals that make them toxic, though poorly understood, vary almost as much as the plants that make them. Although there have been repeated investigations into this phenomenon, the exact reason(s) remain elusive to this day. Still, research has drummed up some interesting data and many great hypotheses aimed at explaining the patterns.

Catalpa nectar has been shown to deter some ants and butterflies but not large bees.

Catalpa nectar has been shown to deter some ants and butterflies but not large bees.

The earliest investigations into toxic nectar gave birth to the pollinator fidelity hypothesis. Researchers realized that meany bees appear to be less sensitive to alkaloids in nectar than are some Lepidopterans. This led to speculation that perhaps some plants pump toxic compounds into their nectar to deter inefficient pollinators, leading to more specialization among pollinating insects that can handle the toxins.

Another hypothesis is the nectar robber hypothesis. This hypothesis is quite similar to the pollinator fidelity hypothesis except that it extends to all organisms that could potentially rob nectar from a flower without providing any pollination services. As such, it is a matter of plant defense.

The nectar of  Cyrilla racemiflora  is thought to be toxic to some bees.

The nectar of Cyrilla racemiflora is thought to be toxic to some bees.

Others feel that toxic nectar may be less about pollinators or nectar robbers and more about microbial activity. Sugary nectar can be a breeding ground for microbes and it is possible that plants pump toxic compounds into their nectar to keep it "fresh." If this is the case, the antimicrobial benefits could outweigh the cost to pollinators that may be harmed or even deterred by the toxic compounds.

Finally, it could be that toxic nectar may have no benefit to the plant whatsoever. Perhaps toxic nectar is simply the result of selection for defense compounds elsewhere in the plant and therefore is expressed in the nectar as a result of pleiotropy. If this is the case then toxic nectar might not be under as strong selection pressures as is overall defense against herbivores. If so, the plants may not be able to control which compounds eventually end up in their nectar. Provided defense against herbivores outweighs any costs imposed by toxic nectar then plants may not have the ability to evolve away from such traits.

Where Spathodea campanulata is invasive, its nectar causes increased mortality in native bee hives.

Where Spathodea campanulata is invasive, its nectar causes increased mortality in native bee hives.

So, where does the science land us with these hypotheses? Do the data support any of these theories? This is where things get cloudy. Despite plenty of interest, evidence in support of the various hypotheses is scant. Some experiments have shown that indeed, when given a choice, some bees prefer non-toxic to toxic nectar. Also, toxic nectar appears to dissuade some ants from visiting flowers, however, just as many experiments have demonstrated no discernible effect on bees or ants. What's more, at least one investigation found that the amount of toxic compounds within the nectar of certain species varies significantly from population to population. What this means for pollination is anyone's' guess.

It is worth noting that most of the pollination-related hypotheses about toxic nectar have been tested using honeybees. Because they are generalist pollinators, there could be something to be said about toxic nectar deterring generalist pollinators in favor of specialist pollinators. Still, these experiments have largely been done in regions where honeybees are not native and therefore do not represent natural conditions.

Simply put, it is still too early to say whether toxic nectar is adaptive or not. It could very well be that it does not impose enough of a negative effect on plant fitness to evolve away from. More work is certainly needed. So, if you are someone looking for an excellent thesis project, here is a great opportunity. In the mean time, do yourself a favor and don't eat any mad honey.

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2] [3] [4] [5] [6]

 

 

Delayed Greening

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It goes without saying that leaves are vital to the existence of any photosynthetic plant. They are, after all, the food making organs. This is why plants go to great lengths to protect them. Losing leaves can be extremely costly. One of the most intriguing methods of anti-herbivory in plants is known as delayed greening. Flushes of new growth bathed in reds, whites, and light greens can color forests from top to bottom. 

Delayed greening is a matter of resource conservation and herbivore protection. The cellular machinery that makes photosynthesis possible is costly to produce. It requires large amounts of nutrients, such as nitrogen and phosphorus, that are often in short supply. If a plant can help it, its best to avoid losing a leaf chock full of these precious materials. Delayed greening does just that. 

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Essentially, the process proceeds exactly as it sounds. Young shoots and leaves gradually expand over time, becoming more green as they grow tougher and better defended. When a plant packs its leaves full of photosynthetic machinery right out of the gates, when leaves are small and tender, it runs the risk of loosing all of its investment to a hungry herbivore. In contrast, non-photosynthetic leaves are thought to be less palatable to herbivores because they simply do not have the nutritional content of photosynthetic leaves.

By delaying the development of chlorophyll until the leaf is fully expanded and a bit tougher, some plants are maximizing the chances of successfully increasing their photosynthetic capacity over time. Research has shown that plants that exhibit the delayed greening strategy experience significant reductions in the amount of herbivory over time. What they lose with the lack of photosynthesis early on they make up for in the fact that such leaves last longer.  

Photo Credits: [1] [2]

Further Reading: [1] [2] [3]

 

Floral Mucilage

Spend enough time around various Bromeliads and you will undoubtedly notice that some species have a rather gooey inflorescence. Indeed, floral mucilage is a well documented phenomenon within this family, with something like 30 species known to exhibit this trait. It is an odd thing to experience to say the least.

The goo takes on an interesting consistency. It reminds me a bit of finding frog spawn as a kid. Their brightly colored flowers erupt from this gooey coating upon maturity and the seeds of some species actually develop within the slimy coating. Needless to say, the presence of mucilage in these genera has generated some attention. Why do these plants do this?

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Some have suggested that it is a type of reward for visiting pollinators. Analysis of the goo revealed that it is 99% water and 1% carbohydrate matrix with no detectable sugars or any other biologically useful compounds. As such, it probably doesn't do much in the way of attracting or rewarding flower visitors. Another hypothesis is that it could offer antimicrobial properties. Bromeliads are most often found in warm, humid climates where fungi and bacteria can really do a number. Again, no antimicrobial compounds were discovered nor did the mucilage show any sort of growth inhibition when placed in bacterial cultures.

It is far more likely that the mucilage offers protection from hungry herbivores. Flowers are everything to a flowering plant. They are, after all, the sexual organs. They take a lot of energy to produce and are often brightly colored, making them prime targets for a meal. Anything that protects the flowers during development would be a boon for any species. Indeed, it appears that the mucilage acts as a physical barrier, protecting the developing flowers and seeds. One study found that flowers protected by mucilage received significantly less damage from weevils than those without mucilage.

The mucilage could also provide another benefit to Bromeliads. Because these plants rely on water stored in the middle of their rosette (the tank, as it is sometimes called), some species may also gain a nutritional benefit as well. Bromeliad flowers emerge from this central tank so anything that gets stuck in the mucilage may eventually end up decomposing in the water. Since nutrients are absorbed along with the water, this could be an added meal for the plant. To date, this has not been confirmed. More work is needed before we can say for sure.

Photo Credit: [1] [2]

Further Reading: [1] [2] [3] [4]

 

Trees Know Who Nibbles

Not being able to escape form your predators makes for an interesting challenge. Plants, being the static organisms that they are, have risen to this challenge in some amazing ways. From thorns, to hairs, and even chemical warfare, there is no end to the strategies plants have evolved to discourage herbivores.

These adaptations come at a cost. Whether its physical or chemical, defenses require ample resources to produce. That is why so many plant species have evolved induced defense mechanisms. They don't bother producing their chemical cocktails until they sense that herbivores are munching on their tissues. Whereas the literature is rife with examples of insect-induced defenses in plants, few studies have ever investigated whether plants can sense mammalian herbivory. 

A 2016 paper published in Functional Ecology suggests that some trees certainly can. By looking at the responses of two different tree species, sycamore maple (Acer pseudoplantanus) and European beech (Fagus sylvatica), the research team found that trees seem to be able to distinguish between being clipped and being browsed, in this case, by deer. Deer populations are at historically high densities. This has had severe ramifications on forest health and composition. Tree saplings are especially vulnerable, so much so that we are witnessing an alarming decrease in tree replacement over time. 

The research team tested if trees could sense herbivory in a pretty ingenious way. They set out into the forest with pruners. Saplings were subjected to two different treatments - simple pruning and pruning followed by the addition of deer saliva. The team then took a look at how each tree responded on a molecular level. What they found was quite startling. Trees that were subjected to pruning alone began producing a class of hormones called jasmonates. This was not surprising as jasmonates are involved in some generic plant defenses. The most interesting results came from the treatments in which deer saliva was added.

With the addition of deer saliva to pruned beech twigs, it was discovered that the trees increased their production of metabolites related to growth of buds and leaves. They also found that the addition of deer saliva caused an increase in the production of defense compounds, specifically tannins. Tannins bind to proteins in animal guts, making them harder to digest. In maples specifically, they also found an increase in certain types of flavanols, which have shown to have anti-herbivory properties in insects and humans, however, more work is needed to see if they do in fact deter other mammalian herbivores.

Although we still don't know what exactly the trees are responding to in deer saliva, these results nonetheless offer the first evidence of trees not only being able to perceive mammalian herbivores but also responding with an increase in defense compounds. Although they only looked at two tree species, it stands to reason that such responses are wide spread throughout many plant lineages. It also calls into question previous research that used simple pruning as a proxy for herbivory. Taken together, the picture of plants being unresponsive backdrops to more charismatic fauna is entirely erroneous. Plants are proving to be quite "aware" of their environment.

Photo Credit: [1]

Further Reading: [1]

 

 

Sand Armor

Plants go through a lot to protect themselves from the hungry jaws of herbivores. They have evolved a multitude of ways in which to do this - toxins, stinging hairs, thorns, and even camouflage. And now, thanks to research by a team from UC Davis, we can add sand to this list. 

At this point you may be asking "sand?!" Stick with me here. Undoubtedly you have noticed that sticky plants often have bits of whatever substrate they are growing in stuck to their stems and leaves. You wouldn't be the first to notice this. Back in 1996 a term was coined for this very phenomenon. It has been called “psammophory,” which translates to "sand-carrying."

Over 200 species of plants hailing from 88 genera in 34 families have been identified as psammorphorous. The nature of this habit has been an object of inquiry for at least a handful of researchers over the last few decades. Hypotheses have ranged from protection from physical abrasion, reduction of water loss, reduced surface temperature, reduced solar radiation, and protection from herbivory. 

It was this last hypothesis that seemed to stick. Indeed, many plants produce crystalline structures in their tissues (phytoliths, raphides, etc., which are often silica or calcium based) to deter herbivores. Sand, being silica based, is known to cause tooth wear in humans, ungulates, and rodents. Perhaps a coating of sand is enough to drive away insects and other hungry critters looking to snack on a plant. 

By controlling the amount and color of the sand stuck to plants, the researchers were able to demonstrate that plants covered in sand were less palatable to both mammalian and insect herbivores. In total, sand-covered individuals received significantly less damage to their leaves than individuals that had their sand coat removed. By altering the color of the sand, the researchers were able to demonstrate that this was not a function of camouflage. In total, the presence of sand led to an overall increase in fitness due to a decrease in damage over time. These results are the first conclusive evidence in support of psammophory as yet another fantastic plant defense mechanism. 

Photo Credit: Franco Folini (bit.ly/1RApG1R) and Wolfram Burner (
http://bit.ly/1RMNR9V)

Further Reading:
http://onlinelibrary.wiley.com/wol1/doi/10.1890/15-1696/abstract

The Truth About Coffee

Mmm mmm coffee. This wonderful elixir has taken over the world. Though individual tastes and preferences vary, there is no denying that most folks who turn to coffee enjoy its effects as a stimulant. Many an In Defense of Plants post has been written in a coffee-fueled frenzy. Even as I write this piece, I am taking breaks to sip on a warm mug of the stuff. Coffee has plenty of proponents as well as its fair share of nay sayers but the health effects don't really concern me much. Today I would rather talk with you about the shrubs that are behind all of this. 

The coffee we drink comes from a handful of shrubs in the genus Coffea. Native to parts of Africa, these shrubs are distant relatives of plants like buttonbush (Cephalanthus occidentalis) and the bedstraws (Galium sp.). The "beans" that we brew coffee from are not beans at all but rather a type of pit or stone found in the center of a bright red berry. Before they are roasted, the "beans" are actually green. Plants in this genus produce an alkaloid compound known as caffeine. Though it may seem strange, the purpose of caffeine is not to stimulate the human nervous system (though it is a wonderful side effect) but rather it is produced as a defense mechanism for the plant. Making this compound is a complex process that involves many metabolic steps within the tissues of the plant. There are certain factions out there who would like to argue that this is proof against evolution but, as always, evidence seems to be the downfall of their argument. 

Creationists will tell you that the adaptations we see throughout the living world are too complex to have happened by accident. In reality, there is a vast amount of evidence that disputes this. Caffeine is one such example. It has evolved independently multiple times in many different plant lineages. Looking at the genome of coffee, researchers at the University at Buffalo (my alma mater) found that the genes involved in the synthesis of caffeine did not arise all at once. Instead, the genes duplicated multiple times throughout the history of this genus with each duplication coding for another step in the process of producing the caffeine molecule. The interesting part is that each step of this evolutionary process produced a chemical that was itself useful to the plant. The precursor compounds are bitter and toxic to the kinds of animals that like to nibble on the plant. 

As it turns out, the benefits that the plants get from caffeine aren't restricted to defense either. Coffee, as well as other flowering plants such as citrus, produce small amounts of caffeine in their nectar. Researchers at Arizona State University found that bees were 3 times more likely to remember a flowers scent when there was caffeine in the nectar than if there wasn't. This serves a great benefit to the plant producing it because it means that its flowers are much more likely to get pollinated. As it turns out, humans aren't the only species that enjoys a good buzz from caffeine.

Before we get too excited over coffee, we must remember that is definitely has its downside. Worldwide, we humans drink roughly 2.25 billion cups of the stuff every day. In order to produce that much coffee, humans have turned somewhere around 11 million hectares of land into coffee plantations. This has come at an extreme cost to the environment. Also, being a tropical species, the types of habitat used to grow coffee were once lush, tropical rain forests. A majority of coffee consumed around the world is produced in monocultures. Where there once stood towering trees and a lush understory is now an open, chemically-laden field of coffee shrubs. There is hope, however, and it is rising in popularity. 

If you enjoy coffee as much as I do, you should certainly consider switching over to shade grown coffee. I have attached a fair amount of literature at the bottom of this post but the long story short of it is that growing coffee is much less harmful to the environment when it is grown in a forest rather than open plantations. The structural complexity of shade grown coffee farms allows a greater diversity of plant and animal species to coexist with one another. Species diversity and richness are significantly higher on shade grown farms than on open field plantations. 

So, there you have it. Coffee is as complex as it is interesting. We humans are simply lucky to have stumbled across a plant that interacts with our brain chemistry in wonderful ways. Certainly coffee has benefitted in the long run. 

Photo Credit: Ria Tan (http://bit.ly/1pFQD1J)

Further Reading:
http://www.sciencemag.org/content/345/6201/1181.full

https://asunews.asu.edu/20130307_beesandcaffeine


http://s.si.edu/1o6wOaj

http://www.sciencedaily.com/releases/2012/08/120807101357.htm

http://bit.ly/1S6dLVV

Insect Eating Bats Eat More Insects Than Birds in Tropical Forests

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If the early bird gets the worm, it is only because we haven't been observing bats the right way, at least not in the rainforests of Central America. It has long been thought that insects such as katydids and caterpillars exhibit night feeding in order to escape day-active birds. This theory has influenced the way in which researchers investigate insect herbivory in tropical forests. However, recent studies have shown that bats, not birds, are doing the bulk of the insect eating in both natural and man-made habitats. 

In order to accurately investigate the role of insectivorous bats play in limiting herbivory in tropical forests, researchers decided to look at the common big-eared bat (Micronycteris microtis). They wanted to find out exactly how much insect predation could be attributed to these nocturnal hunters. As it turns out, 70% of the bats diet consists of plant eating insects, which is quite significant. Extrapolating upwards, it was apparent that we have been overlooking quite a bit.

Using special exclosures, researchers set out to try to quantify herbivory rates when bats and birds were excluded. What they found was staggering. When birds were excluded from hunting on trees, insect presence went up 65%. When bats were excluded, insect presence skyrocketed by 153%! What this amounts to is roughly three times as much damage to trees when bats are removed - a significant cost to forests. 

To prove that it wasn't only natural forests that were benefitting from the presence of bats, the researchers then replicated their experiments in an organic cacao farm. Again, bats proved to be the top insect predators, eating three times as many insects than birds. This amounts to massive economic benefits to farmers. Bats have long been viewed as the enemies of both the farm as well as the farmers. Research like this is starting to change such perspectives. 

This certainly doesn't diminish the role of birds in such systems. Instead, it serves to elevate bats to a more prominent stature in the healthy functioning of forest ecosystems. Findings such as these are changing the way we look at these furry fliers and hopefully improving our relationship as well. 

Photo Credit: Christian Ziegler - Wikimedia Commons

Further Reading: [1] [2]