Death by Crab Spider, part two

Crab spiders that hunt in flowers prey on pollinating insects. Thus, pollinating insects tend to avoid flowers that harbor crab spiders. We established this in part one. Now we ask, what effect, if any, does this interaction have on a crab spider infested plant’s ability to reproduce? More importantly, what are the evolutionary implications of this relationship?

In a study published in Ecological Entomology earlier this year, Gavini, et al. found that pollinating insects avoided the flowers of Peruvian lily (Alstroemeria aurea) when artificial spiders of various colors and sizes were placed in them. Bumblebees and other bees were the most frequent visitors to the flowers and were also the group “most affected by the presence of artificial spiders, decreasing the number of flowers visited and time spent in the inflorescences.” This avoidance had a notable effect on plant reproduction, namely a 25% reduction in seed set and a 15% reduction in fruit weight. The most abundant and effective pollinator, the buff-tailed bumblebee, was deterred by the spiders, leading the researchers to conclude that, “changes in pollinator behavior may translate into changes in plant fitness when ambush predators alter the behavior of the most effective pollinators.”

Peruvian lily (Alstroemeria aurea) via wikimedia commons

But missing from this discussion is the fact that crab spiders don’t only eat pollinators. Any flower visiting insect may become a crab spider’s prey, and that includes florivores. In which case, crab spiders can benefit a plant, saving it from reproduction losses by eating insects that eat flowers.

In April of this year, Nature Communications published a study by Knauer, et al. that examined the trade-off that occurs when crab spiders are preying on both pollinators and florivores. Four populations of buckler-mustard (Biscutella laevigata ssp. laevigata) were selected for this study. Bees are buckler-mustard’s main pollinator, and in concurrence with other studies, they significantly avoided flowers when crab spiders were present.  Knauer, et al. also determined that bees and crab spiders are attracted to the same floral scent compound, β-ocimene. This compound not only attracts pollinators, but is also emitted when plants experience herbivory, possibly to attract predators to come and prey on whatever is eating them.

buckler-mustard (Biscutella laevigata) via wikimedia commons

In this study, the predators called upon were crab spiders. Florivores had a notable impact on plants in this study, and the researchers found that when crab spiders were present, florivores were significantly reduced, thereby reducing their negative impact. They also noted that “crab spiders showed a significant preference for [florivore-infested] plants over control plants.”

And so it is, a plant’s floral scent compound attracts pollinators while simultaneously attracting the pollinator’s enemy, who is also called in to protect the flower from being eaten. Luckily, in this case, buckler-mustard is easily pollinated, so the loss of a few pollinators isn’t likely to have a strong negative effect on reproduction. As the authors write, “pollinators are usually abundant and the low number of ovules per flower makes a few pollen grains sufficient for a full seed set.”

crab spider on zinnia

But none of these studies are one size fits all. Predator-pollinator-plant interactions are still not well understood, and there is much to learn through future research. A meta-analysis published in the Journal of Animal Ecology in 2011 looked at the research that had been done up to that point. Included were a range of studies involving sit-and-wait predators (like crab spiders and lizards) as well as active hunters (like birds and ants) and the effects of predation on both pollinators and plant-eating insects. They concluded that where carnivores “disrupted plant-pollinator interactions, plant fitness was reduced by 17%,” but thanks to predation of herbivores, carnivores helped increase plant fitness by 51%. This suggests that carnivores, overall, have a net positive effect on plant fitness.

Many pollinating insects have an advantage over plant-eating insects because they move quickly from flower to flower and plant to plant, unlike many herbivores which move more slowly. This protects pollinators from predation and helps explain why plant-pollinator interactions are not disrupted as easily by carnivores. Additionally, as the authors note, “plants may be buffered against loss of pollination by attracting different types of pollinators, some of which are inaccessible to carnivores.”

But again, there is still so much to discover about these complex interactions. One way to gain a better understanding is to investigate the effects of predators on both pollinators and herbivores in the same study, since many of the papers included in the meta-analysis focused on only one or the other. As far as crab spiders go, Knauer, et al. highlight their importance in such studies. There are so many different species of crab spiders, and they are commonly found on flowers around the globe, so “their impact on plant evolution may be widespread among angiosperms.”

In other words, while we still have a lot to learn, the impact these tiny but skillful hunters have should not be underestimated.

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Death by Crab Spider, part one

When a bee approaches a flower, it is essentially approaching the watering hole. It comes in search of food in the form of pollen and nectar. As is this case with other animals who come to feed at the watering hole, a flower-visiting bee makes itself vulnerable to a variety of predators. Carnivores, like the crab spider, lie in wait to attack.

The flowers of many plants rely on visits from bees and other organisms to assist in transferring pollen from stamens to stigmas, which initiates reproduction; and bees and other flower visitors need floral resources to survive. Crab spiders exploit this otherwise friendly relationship and, in doing so, can leave lasting impacts on both the bees and the flowers they visit.

Species in the family Thomisidae are commonly referred to as crab spiders, a name that comes from their resemblance to crabs. Crab spiders don’t build webs to catch prey; instead they either actively hunt for prey or sit and wait for potential prey to happen by, earning them the name ambush predators. Of the hundreds of species in this family, not all of them hunt for prey in flowers; those that do – species in the genera Misumena and Thomisus, for example – are often called flower crab spiders.

white crab spider (Thomisus spectabilis) on Iris sanguinea — via wikimedia commons

Most crab spiders are tiny – mere millimeters in size – and they have a number of strategies (depending on the species) to obscure their presence from potential prey. They can camouflage themselves by choosing to hunt in a flower that is the same color as they are or, in the case of some species, they can change their color to match the flower they are on. Some species of crab spiders reflect UV light, which bees can see. In doing so, they make themselves look like part of the flower.

Using an Australian species of crab spider, researchers found that honey bees preferred marguerite daisies (Chrysanthemum frutescens) on which UV-reflecting crab spiders were present, even when the scent of the flowers was masked. The spiders’ presence was seen as nectar guides, which “bees have a pre-existing bias towards.” Members of this same research team also determined that both crab spiders and honey bees choose fragrant flowers over non-fragrant flowers, and that, ultimately, “honey bees suffer apparently from responding to the same floral characteristics as crab spiders do.”

Needless to say, crab spiders are crafty. So the question is, when killing machines like crab spiders are picking off a plant’s pollinators, does this affect its ability to reproduce? First let’s consider how pollinators react to finding crab spiders hiding in the flowers they hope to visit.

goldenrod crab spider (Misumena vatia) preying on a pollinator — via wikimedia commons

A study published in Oikos in 2003 observed patches of common milkweed (Asclepias syriaca) – one set was free of crab spiders, the other set was not – and tracked the visitations of four species of bees – the common honey bee and three species of bumble bees. They compared visitation rates between both sets of milkweed patches and found that the smallest of the three bumble bee species decreased its frequency of visitation to the crab spider infested milkweeds. Honey bees also appeared to visit the infested milkweeds less, but the results were not statistically significant. The two larger species of bumble bees continued to forage at the same rate despite the presence of crab spiders.

During the study, crab spiders were seen attacking bees numerous times. Six attacks resulted in successful kills, and of the bees that escaped, 80% left the flower and either moved to a different flower on the same plant, moved to a different plant, or left the patch altogether. These results indicate a potential for the presence of crab spiders to effect plant-pollinator interactions, whether its directly (predation) or indirectly (bees avoiding flowers with crab spiders).

Another study published in Behavioral Ecology in 2006 looked at two species of bees – the honey bee and a species of long-horned bee – and their reactions to the presence of crab spiders on the flowers of three different plant species – lavender (Lavandula stoechas), crimson spot rockrose (Cistus ladanifer), and sage-leaf rockrose (Cistus salvifolius). Honey bees were about half as likely to select inflorescences of lavender when crab spiders were present, and they avoided the crab spider infested flowers of crimson spot rockrose with a similar frequency. On the other hand, the long-horned bee visited the flowers of crimson spot rockrose to the same degree whether or not a crab spider was present.

bee visiting sage-leaf rock rose (Cistus salvifolius) — via wikimedia commons

The researchers then exposed honey bees to the flowers of sage-leaf rockrose that were at the time spider-free but showed signs that crab spiders had recently visited. Some of the flowers featured the scent of crab spiders, others had spider silk attached to them, and others had the corpses of dead bees on them. They found that even when crab spiders were no longer present, the bees could still detect them. Honey bees were particularly deterred by the presence of corpses. The long-horned bees were also exposed to the flowers with corpses on them but didn’t show a significant avoidance of them.

An interesting side note about the presence of silk on flowers. As stated earlier, crab spiders do not spin webs; however, they do spin silk for other reasons, including to tether themselves to flowers while hunting. The authors recount, “on several occasions when an attempted attack was observed during this study, it was only the presence of a silk tether that prevented spiders being carried away from flowers by their much larger prey.”

So, again, if bees are avoiding flowers due to the presence of predators like crab spiders, what effect, if any, is this having on the plants? We will address this question in part two.

When Milkweed Kills

When you think of milkweed, you probably think of the life it supports. The monarch butterfly, for one. As the sole food source for its leaf-eating larvae, monarchs would be a thing of the past if milkweeds disappeared. Numerous other insects feed on its foliage as well, and there are a plethora of organisms that feed on its nectar, including bees, butterflies, beetles, wasps, and other insects, as well as hummingbirds. And speaking of birds, some birds use the silky hairs attached to the seeds to line their nests, while other birds strip stringy fibers from the stems for nest building. And while it is not a major food source for mammals, deer and other animals have been known to sample it. Indeed, milkweed is a veritable life force.

red milkweed beetle (Tetraopes sp.) feeds on milkweed

But it’s also a poisonous plant. The latex sap of milkweed contains cardiac glycosides, among a variety of other toxic chemicals. The plant produces these chemicals to defend itself from herbivory, and so the insects that feed on it have adapted a variety of strategies to avoid being poisoned. Some bite a hole in a leaf vein and wait for the milky sap to drain before proceeding to eat the leaf. Others are able to consume the toxic foliage without being poisoned by it. Some even store the toxic chemicals in their bodies, making themselves poisonous to other organisms that dare consume them.

Aphids on Mexican whorled milkweed (Asclepias fascicularis). One species commonly found on milkweed is the oleander aphid (Aphis nerii), an introduced species that feeds on milkweeds and other plants in the dogbane family.

While milkweed is generally found to be unpalatable to most livestock, those that venture to eat it risk being poisoned and even killed. A guide to milkweed written by the Xerces Society states, “sheep and goats are the most likely to be poisoned because they are browsers and often prefer to feed on weeds over other forages.” Weeds of the West calls Utah milkweed (Asclepias labriformis) “the most poisonous of all western milkweeds,” claiming that “as little as one ounce of green leaf material … can kill an adult sheep.” It also lists swamp milkweed (Asclepias incarnata) as “suspected of causing livestock deaths.” To make matters worse, dead and dried milkweed plants retain their toxicity, which is a problem when they end up in animal feed.

Despite their toxicity, humans have been consuming milkweed for centuries. Young shoots and leaves can be eaten after boiling them several times, refreshing the water each time, and a medicinal tea can be made from the roots. While fatal poisonings of humans haven’t been reported, Nancy Turner and Patrick von Aderkas warn in their book The North American Guide to Common Poisonous Plants and Mushrooms that “uncooked shoots and the mature plants should never be consumed”

But milkweed’s toxic sap is not its only method for killing.

In fact, it may not even be its most deadly. And this is where things get interesting. Last month I arrived at work one morning to find a portion of a dried-up milkweed inflorescence on my desk that had been left there by a friend and co-worker. Stuck to the inflorescence were three, dead, dried-up honey bees, their legs trapped in the slotted hoods of the flowers. Apparently this is a common occurrence; one that is mentioned in nearly every resource about milkweeds that I have read now, and yet I had never heard of it nor seen it until this gift was left for me. I then went out to a patch of milkweed to see this for myself. Sure enough, I found a few dead bees trapped in the flowers of showy milkweed.

dead honey bee stuck in the flowers of showy milkweed (Asclepias speciosa)

Milkweed flowers do not always give up their pollen sacs easily. The slits where the pollinia are found can, on occasion, trap the legs of visiting insects. John Eastman describes this in The Book of Field and Roadside, “insects sometimes become permanently wedged as the fissures trap their feet or the pollinia entangle them, and they die hanging from the flowers.” While milkweed species are native to North America, honey bees are not; they have not evolved alongside the flowers of milkweed, yet they are drawn in, like so many other insects, to the nutritious and abundant nectar.

Native or not, honey bees are not the only insects getting trapped in the flowers. Eastman reports seeing various species of butterflies ensnared as well, and a paper by S.W. Frost lists cluster flies, soldier beetles, and a couple species of moths as unsuspecting victims of these unruly flowers. Frost goes on to observe that, “in spite of the hazards,” bees, wasps, and various other insects “visited the flowers of milkweeds freely.”

In a paper published in 1887, Charles Robertson describes the insect visitors of several different milkweed species. He found an occassional dead insect on the flowers of swamp milkweed, adding that “this occurs only when all or most of the feet are entangled simultaneously, so as to render the insect absolutely helpless.” Observing common milkweed (Asclepias syriaca), Robertson finds that “even when small and short-legged insects succeed in extracting pollinia and inserting them into the stigmatic chambers, they have great difficulty in breaking the retinacula, and often lose their lives in consequence.”

Honey bees were easily the most common victims observed in Robertson’s study, leading him to quip, “it seems that the flowers are better adapted to kill [honey bees] than to produce fruit through their aid.” And a honey bee’s trouble doesn’t always end when she escapes the grasp of the flowers. Pollinia and its connecting tissues can get so tangled around her legs and other body parts that she can no longer forage, subjecting herself to starvation and predation.

To add insult to injury, dead and dying insects stuck to flowers result in another interesting phenomenon. Robertson writes, “many fall prey to predacious insects. I have seen them while still alive, attacked by ants, spiders and [predatory stink bugs].” Eastman adds daddy longlegs to the list of “scavengers” or “cleanup specialists” that come to feed on “flower trapped insects.” As it turns out, visiting the flowers of milkweed can be a dangerous, even deadly, game.

See Also: Idaho’s Native Milkweeds

Eating Weeds: Burdock

If we agree that weeds can be famous while simultaneously being infamous, a list of famous weeds must include burdock. Its fame largely comes from being an inspiration for the hook-and-loop fastener, Velcro. The idea for this revolutionary product came when Swiss inventor, George de Mestral, was removing burs – the dried inflorescences of burdock – from his dog in the early 1940’s. Most of us have experienced this, pulling out burs from animal hair or our own clothing, but few have felt inspired to develop a new product. Infamy reigns supreme.

But burdock’s fame isn’t tied to Velcro. Its tenacious, sticky burs, which house the seeds, have been attaching themselves to humans and other animals for centuries, frustrating those who have to remove them but finding new places to grow in the process. And what better way to pay tribute to this phenomenon than to dress oneself in hundreds of burs and parade around town calling yourself the Burry Man? Lest you think I’m crazy, just such a thing has been part of an annual celebration for over 300 years in a town outside of Edinburgh, Scotland.

burs of common burdock (Arctium minus)

Of course, burdock is more than its burs. Other, perhaps less celebrated features, are its edible roots and shoots. Its leaves are also edible, but most people find them too bitter to bother. Green Deane suggests wrapping the leaves around food to cook on a campfire. Both the roots and shoots can be eaten raw or cooked, and the fermented roots along with dandelion roots are traditional ingredients in the British beverage, dandelion and burdock. The roots, shoots, and leaves of burdock have also had a wide variety of medicinal uses.

Two species of burdock have become naturalized in North America – Arctium minus and Arctium lappa. Both species are biennials or short-lived perennials. They start out as rosettes of large leaves with woolly undersides. The leaves grow to a foot or more long and wide. At this stage burdock is similar in appearance to rhubarb. Burdock has a large taproot, which can extend down to three feet in the ground. The taproot continues to grow as the rosette expands. When the plant has reached a certain size it begins to put up a branching flower stalk. It is in the rosette stage, before the plant bolts, that the taproot should be harvested.

As the flower stalk grows, the plant takes on a pyramidal shape, with the leaves along the stalk getting increasingly smaller with height. The plant can reach several feet tall, with one source describing them as towering up to ten feet. The stalks should be harvested before the plants start flowering. Multiple flower heads are produced at the ends of the branching stalk. The inflorescences are composed of purple, tubular, disc florets that are encased and encircled in a series of hooked bracts. The flower heads resemble thistle flowers, but the plant is easy to distinguish from thistles due to its large, soft leaves. Speaking of the leaves, one photographer found them alluring enough to compile a series of photos of them.

Common burdock (Arctium minus): the woolly undersides of the leaves and the tops of the taproots

While burdock can be nuisance plant, it is not particularly noxious. In The Book of Field and Roadside, John Eastman writes, “Burdock cannot be labeled a truly invasive weed, for it rarely intrudes into cultivated fields. Tilling usually controls and eradicates burdock populations. Its favored havens are the disturbed soils of roadsides, railroads, fence rows, vacant lots, and around sheds and old buildings.” In Wild Urban Plants of the Northeast, Peter Del Tredici also comments on burdock’s preference for minimally maintained locations including “vacant lots and rubble dump sites; the edges of emergent woodlands; the sunny borders of freshwater wetlands, ponds, and streams; and on unmowed highway banks and median strips with frequent salt applications.”

I harvested my burdock roots along an unmaintained fence line surrounding a series of raised flower beds. I chose a simple recipe for making burdock chips that involved peeling the roots, cutting them into thin slices, dressing them with olive oil and salt, and baking them in the oven. Since the author of this recipe mentioned buying burdock from a store, they were probably using Arctium lappa, or greater burdock, which is commonly cultivated, especially in Asian countries. Both species can be prepared in similar ways.

burdock roots

The burdock chips had a pleasant nutty flavor, but they were also a little stringy and tough to chew. If I were to do it again, I would probably use a recipe like this one that involves parboiling and then frying. Sierra suggested grating the roots and frying them in bacon grease, which would probably do the trick. There are also recipes for pickled burdock roots, which would be fun to try.

Because the plants I harvested were still in their rosette stage and there weren’t any other plants in the area that were bolting, I didn’t try the shoots. But I’ll keep my eye out, and when I find some I may have to write a part two.

Eating Weeds: Pineapple Weed

When I wrote about pineapple weed (Matricaria discoidea) last year during the Summer of Weeds, I knew that it was edible but I didn’t bother trying it. Pineapple weed is one of my favorite native weeds (yes, it happens to be a native of northwestern North America). I enjoy its sweet fragrance, its frilly leaves, its “petal”-less flowers, and its diminutive size. I also appreciate its tough nature. Now that I have tried pineapple weed tea, I have another thing to add to this list of pros.

pineapple weed (Matricaria discoidea)

One thing about pineapple weed that always impresses me is its ability to grow in the most compacted soils. It actually seems to prefer them. It is consistently found in abundance in highly trafficked areas, like driveways, parking lots, and pathways, seemingly unfazed by regular trampling. Referring to pineapple weed in one of his books about wildflowers, botanist John Hutchinson wrote, “the more it is trodden on the better it seems to thrive.” This is not something you can say about too many other plants.

Both the leaves and flowers of pineapple weed are edible. The flowers seem to be the more common of the two to consume, generally in tea form. In his book Wild Edible and Useful Plants of Idaho, Ray Vizgirdas writes, “A delicious tea can be made from the dried flowers of the plant. The leaves are edible, but bitter. The medicinal uses of pineapple weed are identical to that of chamomile (Anthemis). Used as a tea it is a carminative, antispasmodic, and mild sedative.” In Wild Urban Plants of the Northeast, Peter Del Tredici writes, “A tea made from the leaves has been used in traditional medicine for stomachaches and colds.”

I harvested my pineapple weed at the end of a dirt parking lot and in an adjacent driveway/pathway. I noted how the pineapple weed’s presence waned as I reached the edges of the parking lot and pathway where, presumably, the ground was less compact. Maybe it has more to compete with there – other weeds – and so it shows up less, or maybe its roots simply “prefer” compact soils. Perhaps a little of both. Once I got my harvest home, I rinsed it off and left it to dry. Later, I snipped off the flower heads and made a tea.

I probably used more water than I needed to, so it was a bit diluted, but it was still delicious. It smelled and tasted a lot like chamomile. Sierra agreed. With a little honey added, it was especially nice. Sierra agreed again. The flowers of pineapple weed can be used fresh or dried. They can also be mixed with other ingredients to make a more interesting tea, like the recipe found here.

If you are hesitant to take the leap into eating weeds, a tea may be the simplest thing you can try. Pineapple weed tea is a great way to ease yourself into it. Apart from maybe having to harvest it from strange places, it probably isn’t much different from other teas you have tried, and, from my experience, it’s delightful.

Lettuce Gone Wild, part two

The lettuce we eat is a close relative to the lettuce we weed out of our gardens. Last week we discussed the potential that wild relatives may have for improving cultivated lettuce. But if wild lettuce can be crossed with cultivated lettuce to create new cultivars, can cultivated lettuce cross with wild lettuce to make it more weedy?

Because so many of our crops are closely related to some of the weeds found along with them or the plants growing in nearby natural areas, the creation of crop-wild hybrids has long been a concern. This concern is heightened in the age of transgenic crops (also known as GMOs), for fear that hybrids between weeds and such crops could create super weeds – fast spreading or highly adapted weeds resistant to traditional control methods such as certain herbicides. To reduce this risk, extensive research is necessary before such crops are released for commercial use.

flowers of prickly lettuce (Lactuca serriola)

There are no commercially available, genetically modified varieties of cultivated lettuce, so this is not a concern when it comes to crop-wild hybrids; however, due to how prevalent weedy species like prickly lettuce (Lactuca serriola) are, hybridization with cultivated lettuce is still a concern. So, it is important to understand what the consequences might be when hybridization occurs.

In a paper published in Journal of Applied Ecology in 2005, Hooftman et al. examined a group of second-generation hybrids (L. sativa x L. serriola), and found that the hybrids behaved and appeared very similarly to non-hybrid prickly lettuce. They also found that the seeds produced by the hybrids had a significantly higher germination rate than non-hybrid plants. This is an example of hybrid vigor. Thus, “if hybridization does occur, this could lead to better performing and thus potentially more invasive (hybrid) genotypes.” However, the authors cautioned that “better performing genotypes do not automatically result in higher invasiveness,” and that much depends on the conditions they are found in, the level of human disturbance, etc.

Another thing to consider is that hybrids are not stable. In an article published in Nature Reviews Genetics in 2003, Stewart et al. adress the “misunderstanding that can arise through the confusion of hybridization and … introgression.” It is wrong to assume that hybrids between crops and wild relatives will automatically lead to super weeds. For this to occur, repeated crosses with parental lines (also known as backcrossing) must occur, and “backcross generations to the wild relative must progress to the point at which the transgene [or other gene(s) in question] is incorporated into the genome of the wild relative.” That is what is meant by “introgression.” This may happen quickly or over many generations or it may never happen at all. Each case is different.

prickly leaf of prickly lettuce (Lactuca serriola)

In a paper published in Journal of Applied Ecology in 2007, Hooftman et al. observe the breakdown of crop-wild lettuce hybrids. They note that “fitness surplus through [hybrid vigor] will often be reduced over few generations,” which is what was seen in the hybrids they observed. One possible reason why this occurs is that lettuce is predominantly a self-crossing species; outcrossing is rare, occurring 1 – 5% of the time thanks to pollinating insects. But that doesn’t mean that a stable, aggressive genotype could never develop. Again, much depends on environmental conditions, as well as rates of outcrossing and other factors relating to population dynamics.

A significant expansion of prickly lettuce across parts of Europe led some to hypothesize that crop-wild hybrids were partly to blame. In a paper published in Molecular Ecology in 2012 Uwimana et al. ran population genetic analyses on extensive data sets to determine the role that hybridization had in the expansion. They concluded that, at a level of only 7% in wild habitats, crop-wild hybrids were not having a significant impact. They observed greater fitness in the hybrids, as has been observed in other studies (including the one above), but they acknowledged the instability of hybrids, especially in self-pollinating annuals like lettuce.

seed head of prickly lettuce (Lactuca serriola)

It is more likely that the expansion of prickly lettuce in Europe is due to “the expansion of favorable habitat as a result of climate warming and anthropogenic habitat disturbance and to seed dispersal because of transportation of goods.” Uwimana et al. did warn, however, that “the occurrence of 7% crop-wild hybrids among natural L. serriola populations is relatively high [for a predominantly self-pollinating species] and reveals a potential [for] transgene movement from crop to wild relatives [in] self-pollinating crops.”

Dischidia and Its Self-contained Watering System

This is a guest post by Jeremiah Sandler.

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I was doing some sunday reading in a plant biology textbook, a section about leaves. It was highlighting leaf-specific adaptations and other cool leaf specializations. I came across a paragraph about a “flower-pot” leaf, and my mind was so blown after reading it I had to literally stand up.

It reads:

Some leaves of the Dischidia [genus], an epiphyte from Australasia, develop into urnlike pouches that become the home of ant colonies. The ants carry in soil and add nitrogeneous wastes, while moisture collects in the leaves through condensation of the water vapor coming from the mesophyll through stomata. This creates a good growing medium for roots, which develop adventitiously from the same node as the leaf and grow down into the soil contained in the urnlike pouch. In other words, this extraordinary plant not only reproduces itself by conventional means but also, with the aid of ants, provides its own fertilized growing medium and flower pots and then produces special roots, which “exploit” the situation.

Naturally I had to look up images of this plant because that’s amazing.

Illustration of Dischidia major (image credit: wikimedia commons)

Dischidia major – cross section of “flower-pot” leaf (photo credit: eol.org)

Dischidia vidalii– cross section of “flower-pot” leaf (photo credit: eol.org)

In shorter words, the plant grows modified leaves that form a little cavity, within which ants live. The ants incidentally carry soil into the cavity, while fertilizing that soil with their waste. The stomata are located on the insides of these cavities, which expel water from the leaves, where it then waters the soil that is located inside the leaves. Not to mention, the outside of those cavities are photosynthesizing all the while.

So, with the help of ants, an epiphytic Dischidia has evolved leaves to bring the soil to itself up in the trees, where it fertilizes and waters itself? SAY WHAT?! That is so damn cool.


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