Bearcorn: A Mysterious Parasite from Eastern North America

Bearcorn (Conopholis americana) is one of those plants that really challenges mainstream assumptions of what a plant should look like. It produces no leaves, no chlorophyll, and all you ever see of it are its strange reproductive structures. One can easily be forgiven for thinking they had encountered some type of fungus.

Bearcorn is an obligate parasite on oak trees. It simply can’t exist without access to oak roots. From what I have been able to gather, the preferred hosts of bearcorn are the red oaks (section Lobatae). That is not to say the exceptions have not been documented. At least one author claims to have found bearcorn attached to the roots of a white oak (Quercus alba) and even earlier work suggests that American chestnut (Castanea dentata) may have served as an occasional host as well. Regardless, if you want to find bearcorn in the woods, you would do well to search out red oaks first.

According to those who have run germination trials, bearcorn seeds must be in close proximity to oak roots in order to germinate. Some sources say that direct contact is needed whereas others claim that seeds have to be close enough to detect root presence. It is likely that some sort of chemical cue is what initiates the process and this makes sense. For a plant that relies completely on another plant for its water and nutritional needs, it doesn’t make much sense for bearcorn seeds to germinate anywhere but near oak roots.

Upon germinating, the tiny seedling needs to act fast before its meager energy reserves are exhausted. If lucky, the growing seedling will come into contact with an oak root and begin developing a strange organ referred to as the nodule or tubercle. Thus begins its parasitic lifestyle. The tubercle continues to grow throughout the life of the plant, developing into an amorphous, woody blob that continues to envelope more and more oak roots. Its within the tubercle that all of the parasitism takes place.

Cells within the bearcorn tubercle penetrate into the vascular tissues of the oak root, stealing all the water and nutrients the plant will ever need. Over time, the bearcorn tubercle coaxes the roots of the oak to fan outward like the crown of a tiny tree. In doing so, bearcorn is effectively increasing the amount of surface area available to make more parasitic connections. Apparently this all comes at great cost to the oak roots. Over time, oak root size within the tubercle greatly diminishes until some completely perish. Considering the size of some bearcorn populations, one could expect the oak host to fight back.

Indeed, it would appear that oaks are not helpless against bearcorn infestations. Examination of the cells within bearcorn tubercles revealed that as the parasite grows, the oak will begin flooding the infected cells with tannin-rich compounds. Apparently this serves to slow the flow of water and nutrients into the tubercle. There is even evidence that some of those tannins are transferred into the bearcorn tubercle, leading some to suggest that the oak is literally poisoning its bearcorn parasites, albeit slowly.

There is a strong possibility that such oak defenses lend to the relatively short lifespan of bearcorn plants. In at least one study I read, no bearcorn individuals over 13 years of age were found and the average age is estimate to be about 10 years. Perhaps just over a decade is about all a bearcorn can hope for once the its oak host begins to fight back. Good thing bearcorn populations can be surprisingly fecund.

Bearcorn plants reach reproductive maturity at after about 3 years of growth. They flower in the spring and that is when they are at their most obvious. Numerous thick, finger-like stems emerge from the ground covered in whirls of cream-colored, tubular flowers. Though a dense population of flowering bearcorn may look like a bonanza for pollinators, they don’t seem to attract a lot of attention. From what I was able to find, bumblebees are pretty much the only insects to visit the flowers, and even then, visitation rates are low. Apparently bearcorn flowers do not produce any detectable scent nor are they full of nectar. I guess the only real reward is a meager helping of pollen.

Photo by Joshua Mayer licensed under CC BY-SA 2.0

No matter, bearcorn has a nice reproductive trick to ensure plenty of seeds are produced each year - it selfs. The anatomy of the flowers is such that, at maturity, the anthers are in direct contact with the stigma. Even if nothing visits a bloom, it will still go on to clone itself year after year. Once fertilized, each flower gives way to a large fruit chock full of seed. This is where the corn part of the name bearcorn comes from. A stem thick with fruits does resemble a strange, albeit juicy ear of corn sitting on the forest floor. The bear part of the name likely has to do with the fact that bear readily consume bearcorn fruits, stem and all. Working in the southern Appalachian Mountains, I can’t tell you how many times I came across bear scat absolutely loaded with bearcorn fruits and seeds. It’s not just bear either, deer are also very interested in bearcorn fruits.

Lucky for bearcorn, its seeds pass through the guts of these animals unharmed. Hopefully, with a bit of luck, at least one of these animals will make a deposit in an oak-rich region of the forest. With even more luck, some of those seeds might even find themselves nestled in near an oak root to begin the process anew.

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

When Trillium Flowers Go Green

The first time I encountered a white trillium (Trillium grandiflorum) with green stripes on its flowers, I thought I had found a new variant. I excitedly took a bunch of pictures and, upon returning home, shared them among friends. It didn’t take long for someone far more informed than me to point out that this was not a new variant of this beloved plant. What I had found was signs of an infection.

The green stripes on the petals are the result of a very specific bacterial infection. The bacteria responsible belongs to a group of bacterial parasites collectively referred to as phytoplasmas. Phytoplasmas are not unique to trillium. In fact, these bacteria can be found around the world and infect many different kinds of plants from coconuts to sugarcane. Indeed, most of the research on phytoplasmas is motivated by their impacts on agriculture. Despite the damage they can cause, their natural history is absolutely fascinating.

Phytoplasmas are obligate parasites. They can only live long-term inside the phloem of their preferred host plants. Once inside the plant, phytoplasmas begin tinkering with cell expression, causing an array of different symptoms that (to the best of my knowledge) depend on their botanical host. In the case of trillium, phytoplasma infection causes a change in the flower petals. By altering gene expression, petal cells becoming increasingly leaf-like, resulting in the green striping I had observed. That isn’t all the phytoplasma does either. Infections usually result in complete sterilization of the flower. I have even heard some reports that the infected plants are also weakened to the point that they eventually die.

Why the phytoplasma do this has to do with their bizarre life cycle. Now, to be fair, much of what I have been able to gather on the subject comes from research done on other plant species. Still, there are enough commonalities among phytoplasma infections that I strongly suspect they apply to the trillium system as well. Nevertheless, take what I am saying here with a grain of salt.

As mentioned, phytoplasma can only exist long-term within the phloem of their plant host. They don’t produce any sort of fruiting bodies, nor are they transferred by air or contact with tissues. This creates a bit of an issue when it comes to finding new hosts, especially if infection inevitably results in the death of the plant. This is the point in which a vector must enter the picture.

The vector in question in many cases are sap-feeding insects like leafhoppers. Leafhoppers use their needle-like proboscis to pierce the phloem and suck out sap. It’s this feed behavior that phytoplasma capitalize on to complete their lifecycle. Moreover, the phytoplasma don’t do so passively. Just as the phytoplasma alter the gene expression in the petal cells, they can also alter the expression of genes involved in plant defenses.

Research on infected Arabidopsis plants has shown that phytoplasma cause the plant to decrease production of a hormone called jasmonate. This is fascinating because jasmonate is involved in defending plants against herbivory. It was found that when plants produced less jesmonate, leafhoppers were 30%-60% more likely to lay eggs on those plants. Essentially, the phytoplasma are reducing the plants’ defenses in such a way that there is a greater chance that they will be fed on by a greater number of sap-suckers.

As leafhoppers feed on the sap of infected plants, they inevitably suck up plenty of phytoplasma in the process. Through a complex series of events, the ingested phytoplasma eventually make their way into the salivary glands of the leafhopper. Then, as the leafhopper moves from plant to plant, piercing the phloem to feed, it inevitably transfers some of the phytoplasma in its saliva into a new host, thus completing the lifecycle of these plant parasites.

To bring it back to those green stripes on the trillium flowers, I suspect that by altering the petal cells to look more like leaves, the phytoplasma may be “encouraging” leafhoppers to concentrate their feeding on infected tissues. However, this is purely speculation on my part. The lack of data outside the agricultural realm represents an important scientific void that needs filling.

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

When the Going Gets Tough, Desert Mistletoes Cooperate

Sure, parasites can be a drain on their host, but for those parasites whose entire life depends on a living host, it doesn’t pay to kill. Such is the case for the desert mistletoe (Phoradendron californicum). These plants simply can’t live without the water and nutrients they receive from their host trees. But what happens when more than one mistletoe infects a single tree? One would think that supporting multiple mistletoes would be a dangerous drain on the host tree. However, recent research based in the Sonoran Desert suggests that desert mistletoe has a trick up its stems that involves a bit of communication with its neighbors.

Desert mistletoe isn’t completely reliant on its host for all of its nutritional needs. Though lacking leaves, the desert mistletoe is fully capable of photosynthesis via its tangled mass of green stems. Most of what desert mistletoes extract from their host consists of water and other nutrients they can’t acquire themselves. However, desert mistletoes rarely operate alone. Thanks to their nutritious berries and the territorial habits of the birds that disperse them, multiple mistletoe individuals often wind up parasitizing the same tree.

Heavy infestations may sound like a death sentence for the host tree, especially in the harsh Sonoran climate. However, by manipulating the mistletoe loads on various trees and observing how mistletoes and their hosts respond, researchers have discovered that mistletoes can apparently sense their neighbors and alter their behavior accordingly.

During dry periods, trees become stressed for both water and nutrients. For mistletoes growing on a stressed tree, it doesn’t make much sense from an evolutionary standpoint to increase their demand on the host during these times. Instead, mistletoes growing on stressed trees actually increased the amount of photosynthesis they perform without increasing the amount of water they extract from their host. By altering their metabolism in this way, the mistletoes do not add any extra burden to their already stressed host tree but nonetheless maintain their own fitness.

Amazingly, the situation got even more interesting when researchers experimentally removed some mistletoes. Somehow, depending on their position on their host tree, some remaining mistletoes can sense that their competitors had been removed. When this happens, they don’t go into overdrive and start exacting a greater share of resources from their host. Instead, the remaining mistletoe appear to sense that they no longer have to compete as much and adjust their water and nutrient uptake in such a way that actually allows their host to benefit as well.

Certainly these findings generate more questions than they answer. First, how do mistletoes sense their neighbors? Given their direct links with the host vascular tissues, they could be sensing signals from other parasites that way. There is also the potential for airborne signal detection as well. Also, do mistletoes behave differently when growing near related individuals versus strangers? What researchers have ultimately uncovered is a fascinating coevolutionary system in desperate need of more attention.

Further Reading: [1]

A Newly Described Fungus That Mimics Flowers

(A) Young yellow-orange pseudoflower. (B) Mature pseudoflower. (C) Longitudinal section of an infected X. surinamensis inflorescence. (D) Healthy yellow flower of X. surinamensis shown for comparison. [SOURCE]

Imagine there was a fungus that was able to hijack human reproductive structures so that it could reproduce. Though this sounds like the basis of a strange science fiction story, a similar situation to this has just been described from Guyana between two species of yellow-eyed grass (Xyris setigera & X. surinamensis) and a newly described species of fungus called Fusarium xyrophilum.

Fungi that hijack plant reproductive systems are pretty rare in nature, especially when you consider the breadth of interactions between these two branches on the tree of life. What makes this newly described case of floral hijacking so remarkable is the complexity of the whole process. It all begins when an infected Xyris host begins to produce its characteristically lanky inflorescence.

At first glance, nothing would appear abnormal. The floral spike elongates and the inflorescence at the tip gradually matures until the flowers are ready to open. Even when the “flower” begins to emerge from between the tightly packed bracts the process seems pretty par for the course. Gradually a bright yellow, flower-like structure bursts forth, looking very much like how a bright yellow Xyris flower should look. However, a closer inspection of an infected plant would reveal something very different indeed.

Instead of petals, anthers, and a pistil, infected inflorescences produce what is called a pseudoflower complete with petal-like structures. This pseudoflower is not botanical at all. It is made entirely by the Fusarium fungus. Amazingly, these similarities are far from superficial. When researchers analyzed these pseudoflowers, they found that they are extremely close mimics of an actual Xyris flower in more than just looks. For starters, they produce pigments that reflect UV light in much the same way that actual flowers do. They also emit a complex suite of volatile scent compounds that are known to attract pollinating insects. In fact, at least one of those compounds was an exact match to a scent compound produced by the flowers of these two Xyris species.

So, why would a fungus go through all the trouble of mimicking its hosts flowers so accurately? For sex, of course! This species of Fusarium cannot exist without its Xyris hosts. However, Xyris don’t live forever and for the cycle to continue, Fusarium must go on to infect other Xyris individuals. This is where those pseudoflowers come in. Because they so closely match actual Xyris flowers in both appearance and smell, pollinating bees treat them just like flowers. The bees land on and investigate the fungal structure until they figure out there is no reward. No matter, they have already been covered in Fusarium spores.

As the bees visit other Xyris plants in the area, they inevitably deposit spores onto each plant they land on. Essentially, they are being coopted by the fungus in order to find new hosts. By mimicking flowers, the Fusarium is able to hijack plant-pollinator interactions for its own reproduction. It is not entirely certain at this point just how specific this fungus is to these two Xyris species. A search for other potential hosts turned up only a single case of it infecting another Xyris. It is also uncertain as to how much of an impact this fungus has on Xyris reproduction. Though the fungus effectively sterilizes its host, researchers did make a point to mention that Xyris populations may actually benefit from having a few infected plants as the pseudoflowers last much longer than the actual flowers and therefore could serve to attract more pollinators to the area over time. Who knows what further investigations into the ecology of this bizarre system will reveal.

Photo Credit: [1]

Further Reading: [1]

When is a mushroom not a mushroom? When it is a Maltese mushroom, of course!

Photo by Hans Hillewaert licensed under CC BY-ND 2.0.

Meet Cynomorium coccineum aka the Maltese mushroom. Despite the common name and overall appearance, this is not a fungus. It is indeed a plant. Cynomorium coccineum is a holoparasite. It produces no chlorophyl of its own and relies solely on a host plant for all of its water and nutrient needs. It is said to parasitize the roots of halophytes or salt-loving plants and thus, is most commonly found growing in salt marshes in addition to dry, sandy habitats in coastal areas.

Native to the Mediterranian region and extending into parts of Afghanistan, Saudi Arabia, Iran, and Central Asia, this species is really only ever found during the rainy season. Most of its life is spent underground, emerging only to display its flowers. Only when enough energy has been garnished from the host will this plant throw up these strange flower spikes. As you can tell from the picture, the spikes are jam packed with highly reduced flowers. The flowers give off a scent that has been likened to cabbage. It is thought that flies take up the bulk of the pollination of these blooms.

Photo by Alastair Rae licensed under CC BY-ND 2.0.

Photo by Hans Hillewaert licensed under CC BY-ND 2.0.

As you can probably guess by its strange appearance, the taxonomic affinity of this strange parasite has been the subject of much debate. For a long time, many botanists placed it in the family Balanophoraceae but more recent genetic work suggests it belongs in its own family, Cynomoriaceae. It is the only genus within that family but interestingly enough, Cynomoriaceae is located within the order Saxifragales, somewhere near Crassulaceae, making it a distant relative of stonecrops like sedum. No matter where its located on the tree of life, Cynomorium coccineum is surely one of the strangest plants on Earth.

Photo Credits: [1] [2]

Further Reading: [1] [2]

Opossum Pollination of a Peculiar Parasite

Floral traits can provide us with insights into the types of pollinators most suited for the job. For many flowering plants, the relationship is relatively easy to understand, but check out the flowers of Scybalium fungiforme. You would be completely excused for not even realizing that these bizarre structures belonged to a plant. The anatomy of those flowers would leave most of asking “what on Earth do they attract?” The answer to this are opossums!

Scybalium fungiforme hails from a peculiar family of parasitic plants called Balanophoraceae and is native to the Atlantic forests of Brazil. Members of this family can be found in tropical regions around the globe and all of them are obligate root holoparasites. Essentially this means that all one ever sees of these plants are their strange flowers. The rest of the plant lives within the vascular system of a host plant’s roots.

The adorable big-eared opossums (Didelphis aurita).

Scybalium fungiforme is particularly strange in that its flowers are covered in scale-like bracts. As such, accessing the flowers would be difficult for most animals. Because its strange blooms superficially resemble some marsupial and rodent pollinated Proteaceae in Australian and South Africa, predictions of a non-flying mammal pollination syndrome were about the only explanations that made sense. Now, with the help of night vision cameras, this prediction has been vindicated.

They key to this unique pollination syndrome lies in those bracts and an interesting aspect of opossum anatomy. Until the scale-like bracts are removed, not much is able to access the floral parts inside. Luckily big-eared opossums (Didelphis aurita) come equipped with opposable toes on their back feet. Upon locating the flowers of S. fungiforme, the opossum uses its back feet to remove the bracts. This unveils a bounty of nectar within. As the opossum feeds, its furry little snout gets covered in pollen. When the opossum visits subsequent flowers throughout the night, pollination is achieved.

Floral visitors of Scybalium fungiforme. b) The big-eared opossum, Didelphis aurita drinking nectar on a plant with five inflorescences (one male and four females). c) The montane grass mouse, Akodon montensis, visiting a plant with about 10 inflorescences and drinking nectar on a female one. d) The Violet-capped Woodnymph hummingbird, Thalurania glaucopis visiting a male and e) a female inflorescence. f) detail of an A. angulata wasp manipulating a male flower to eat pollen. g) Agelaia angulate visiting a female inflorescence with the head inserted among flowers to reach the nectar secreted in the inflorescence receptaculum.

Interestingly, activity doesn’t end when the opossums are done. Enough nectar often remains by the next day that a suite of other animals come to pay a visit to these strange blooms. Day time visitation of S. fungiforme consisted largely of wasps, bees, and even a mouse or two. Researchers were also lucky enough to witness Violet-capped Woodnymph hummingbirds (Thalurania glaucopis) repeatedly visit the flowers for a sip of nectar. It would appear that although the main pollinators of this strange parasite are opossums, the removal of the bracts opens up the flowers for plenty of secondary pollinators as well.

Though this is by no means the only plant to be pollinated by non-flying mammals, this pollination syndrome certainly broadens our understanding of the evolution of pollination syndromes.

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

Further Reading: [1]

How radioactive carbon from nuclear bomb tests can tell us what parasitic orchids are eating

Yoania japonica. Photo by Qwert1234 licensed by CC BY-NC-SA 4.0

Historically, non-photosynthetic plants were defined as saprotrophs. It was thought that, like fungi, such plants lived directly off of decaying materials. Advances in our understanding have since revealed that parasitic plants don’t do any of the decaying themselves. Instead, those that aren’t direct parasites on the stems and roots of other plants utilize a fungal intermediary. We call these plants mycoheterotrophs (fungus-eaters). Despite recognition of this strangely fascinating relationship, we still have much to learn about what kinds of fungi these plants parasitize and where most of the nutritional demands are coming from.

It is largely assumed that most mycoheterotrophic plants are parasitic on mycorrhizal fungi. This would make them indirect parasites on other photosynthetic plants. The mycorrhizal fungi partner with photosynthetic plants, exchanging soil nutrients for carbon made by the plant during photosynthesis. However, this is largely assumed rather than tested. New research out of Japan has shown a light on what is going on with some of these parasitic relationships and the results are a bit surprising. What’s more, the methods they used to better understand these parasitic relationships are pretty clever to say the least.

Cyrtosia septentrionalis Photo by Qwert1234 licensed by CC BY-NC-SA 4.0

Photosynthesis involves the uptake of and subsequent breakdown of CO2 from the atmosphere. The carbon from CO2 is then used to build carbohydrates, which form the backbone of most plant tissues. Not all carbon is created equal, however, and by looking at ratios of different carbon isotopes in living tissues, scientists can better understand where the carbon came from. For this research, scientists utilized an isotope of carbon called 14C.

Eulophia zollingeri photo by Vinayraja licensed by CC BY-NC-SA 3.0

14C is special because it is not as common in our atmosphere as other isotopes of carbon such as 12C and 13C. One of the biggest sources of 14C in our atmosphere were nuclear bomb explosions. From the 1950’s until the Partial Nuclear Test Ban in 1963, atomic bomb tests were a regular occurrence. During that time period, the concentration of 14C in our atmosphere greatly increased. Any organism that was fixing carbon into its tissues during that span of time will contain elevated levels of 14C compared to the other carbon isotopes. Alternatively, anything fixing carbon today, say via photosynthesis, will have considerably reduced levels of 14C in its tissues.

Gastrodia elata Photo by Qwert1234 licensed by CC BY-NC-SA 4.0

By looking at the ratios of 14C in the tissues of parasitic plants, scientists reasoned that they could assess the age of the carbon being utilized. If more 14C was present, the source of the carbon could not come from today’s atmosphere and therefore not from recent photosynthesis. Instead, it would have to come from older sources like decaying wood of long-dead trees. In other words, if parasitic plants were high in 14C, then the scientists could reasonably conclude that they were parsitizing wood-decaying saprotrophic fungi. If the plants were high in 12C or 13C, then they could conclude that they were partnering with mycorrhizal fungi instead, which were obtaining carbon from present-day photsynthesis.

The researchers looked at 10 different species of parasitic plants across Japan, most of which were orchids. They analyzed their tissues and ran analyses on the carbon molecules within. What they found is that 6 out of the 10 plants contained much higher levels of 12C and 13C in their tissues, which points to mycorrhizal fungi as their host. However, for the 4 remaining species (Gastrodia elata, Cyrtosia septentrionalis, Yoania japonica and Eulophia zollingeri), the ratios of 14C were considerably higher, meaning their host fungi were eating dead wood, not partnering with photosynthetic plants near by.

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Indeed, it appears that at least some mycoheterotrophic plants are benefiting from saprotrophic rather than mycorrhizal fungi. Those early assumptions into the livelihood of such plants were not as far off the mark after all. This is very exciting research that opens the door to a much deeper understanding of some of the strangest plants on our planet.

LEARN MORE ABOUT MYCOHETEROTROPHIC PLANTS IN EPISODE 234 OF THE IN DEFENSE OF PLANTS PODCAST

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

Further Reading: [1] [2]

The Smallest of the Giants

Photo by Edwino S. Fernando [source]

There are a lot of cool ways to discover a new species but what about tripping over one? That is exactly how Rafflesia consueloae was found. Researchers from the University of the Philippines Los Baños were walking through the forest back in 2014 when one of them tripped over something. To their surprise, it was the bloom of a strange parasitic plant.

This was an exciting discovery because it meant that that strange family of holoparasitic plants called Rafflesiaceae just got a little bit bigger. Rafflesiaceae is famous the world over for the size of its flowers. Whereas the main body of plants in this family consists of tiny thread-like structures living within the tissues of forest vines, the flowers of many are huge. In fact, with a flower 3 feet (1 meter) in diameter, which can weigh as much as 24 lbs. (11 kg), Rafflesia arnoldii  produces the largest flower on the planet. This new species of Rafflesia, however, is a bit of a shrimp compared to its cousins.

In fact, R. consueloae produces the smallest flowers of the genus. Of the individuals that have been found, the largest flower clocked in at 3.83 inches (9.37 cm) in diameter. Needless to say, this was an exciting discovery and those responsible for it quickly set about observing the plant in detail. Cameras were set up to monitor flower development as well as to keep track of any animals that might pay it a visit. It turns out that, like its cousins, R. consueloae appears to be a specialist parasite on a group of vines in the genus Tetrastigma.

One of the unique characteristics of R. consueloae, other than its size, is the fact that its flowers don’t seem to produce any noticeable scent. This is a bit odd considering that its cousins are frequently referred to as “corpse flowers” thanks to the fact that they both look and smell like rotting meat. That is not to say that this species produces no scent at all. In fact, researchers noted that the fruits of R. consueloae smell a bit like coconut.

Its discoverers were quick to note that the discovery of such a strange parasitic plant in this particular stretch of forest is exciting because of the state of disrepair the forest is in. This region has suffered heavily from deforestation and fragmentation and it has long been thought that such specialized parasites like those in the genus Rafflesia could not persist after logging. As such, this discovery offers at least some hope that they may not be as sensitive as we once thought. Still, that does not mean that R. consueloae is by any means secure in its future.

To date, R. consueloae has only been found growing in two localities in Pantabangan, Phillippines. Though it is possible that more populations will be found growing elsewhere, its limited distribution nonetheless places it at high risk for extinction. Further habitat loss and the potential for anthropogenic forest fires are considerable threats to these plants and the hosts they simply can’t live without.

Despite plenty of observation, no one is quite sure how this species manages to reproduce successfully. Individual flowers are said to be either male or female but without a scent, its hard to say who or what pollinates them. Similarly, it still remains a mystery as to how R. consueloae (or any of its relatives for that matter) accomplish seed dispersal. Some small mammals were seen feeding on fruits but what happens after that is anyone’s guess. It seems like the various Rafflesiaceae still have many mysteries to be solved.

Photo Credit: [1]

Further Reading: [1]

Is Love Vine Parasitizing Wasps?

Photo by David Eickhoff licensed under CC BY 2.0

No, that's not dodder (Cuscuta sp.), its love vine (Cassytha filiformis), a member of the same family as the avacados in your kitchen (Lauraceae). It is a pantropical parasite that makes its living stealing water and nutrients from other plants. To do so, it punctures their vascular tissues with specialized structures called "haustoria." Amazingly, a recent observation made in Florida suggests that this botanical parasite may also be taking advantage of other parasites, specifically gall wasps.

Gall wasps are also plant parasites. They lay their eggs in developing plant tissues and the larvae release compounds that coax the plant to form nutrient-rich galls packed full of starchy goodness. Essentially you can think of galls as edible nursery chambers for the wasp larvae. While looking for galls on sand live oak (Quercus geminata) growing in southern Florida, Dr. Scott Egan and his colleagues noticed something odd. A small vine seemed to be attaching itself to the galls.

Love vine draping a host plant. Photo by Forest & Kim Starr licensed under CC BY 3.0

The vine in question was none other than love vine and they were attached to galls growing on the underside of the oak leaves. What is strange is that, of all of the places that love vine likes to attach itself to its host (new stems, buds, petioles, and on the top and edge of leaves), the only time this vine showed any "interest" in the underside of oak leaves was when galls were present. Obviously this required further investigation.

The team discovered that at least two different species of gall wasps were being parasitized by love vine - one that produces small, spherical galls on the underside of oak leaves and one that forms large, multi-chambered galls on oak stems. Upon measuring the infected and uninfected galls, the team discovered that there were significant differences that could have real ecological significance.

(A) Cassytha filiformis vine attaching haustoria to a leaf gall induced by the wasp Belonocnema treatae on the underside of their host plant, Quercus geminata. (B) Labeled graphic of insect gall, parasitic vine, and vine haustoria. (C) Box plots of leaf gall diameter for unparasitized galls (control) and galls that have been parasitized by C. filiformis. (D) Proportion of B. treatae leaf galls that contained a dead ‘mummified’ adult for unparasitized galls (control) and galls that have been parasitized by the vine C. filiformis. [SOURCE]

For the spherical gall wasp, infected galls tended to be much larger, however, the team feels that this may actually be due to the fact that the vine "prefers" larger galls. Astonishingly, larvae living in the infected galls were 45% less likely to survive. For the multi-chambered gall wasp, infection by love vine was associated with a 13.5% decrease in overall gall size. They suggest this is evidence that love vine is having net negative impacts on these parasitic wasps.

Subsequent investigation revealed that these wasps were not alone. In total, the team found love vine attacking the galls of at least two other wasps and one species of gall-making fly (though no data were reported for these cases). To be sure that love vine was in fact parasitizing these galls, they needed to have a closer look at what the vine was actually doing.

Figure S2. (A) Cassytha filiformis vine attaching haustoria to a leaf gall induced by the wasp Callirhytis quercusbatatoides on the stem of their host plant, Quercus geminata. (B) Labeled graphic of insect gall, parasitic vine, and vine haustoria on C. quercusbatatoides. (C) Exemplar of parasitic vine wrapping tightly around the stem directly proximate to a gall induced by the wasp Disholcaspis quercusvirens on Q. geminata. (D) Field site where love vine, C. filiformis, is attacking the sand live oak, Q. geminata, and many of the gall forming wasps on the same host plant. [SOURCE]
 

Dissection of the galls revealed that the haustoria were plugged into the gall itself, not the wasp larvae. However, because the larvae simply cannot develop without the nutrients and protection provided by the gall, Eagan and his colleagues conclude that these do indeed represent a case of a parasite being parasitized by another parasite.

At this point, the next question that must be asked is how common is this in love vine or, for that matter, across all other parasitic plants that utilize haustoria. Considering that parasites of parasites are nothing new in the biosphere, it is a safe bet that this will not be the last time this phenomenon is discovered.

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

Further Reading: [1]

From Herbivore to Pollinator Thanks to a Parasitoid

In the Atlantic forests of Brazil resides a small orchid known scientifically as Dichaea cogniauxiana. Like most plant species, this orchid experiences plenty of pressure from herbivores. It faces rather intense pressures from two species of weevil in the genus Montella. These weevils are new to science and have yet been given full species status. What's more, they don't appear to eat the leaves of D. cogniauxiana. Instead, female weevils lay eggs in the developing fruits and the larvae hatch out and consume the seeds within. In other words, they treat the fruits like a nursery chamber.

This is where this relationship gets interesting. You see, the weevils themselves appear to take matters into their own hands. Instead of waiting to find already pollinated orchids, an event that can be exceedingly rare in these dense forests, these weevils go about pollinating the orchids themselves. Females have been observed picking up orchid pollinia and depositing the pollen onto the stigmas. In this way, they ensure that there will be developing fruits in which they can raise their young.

Left unchecked, the weevil larvae readily consume all of the developing seeds within the pod, an unfortunate blow to the reproductive efforts of this tiny orchid. However, the situation changes when parasitoid wasps enter the mix. The wasps are also looking for a place to rear their young but the wasp larvae do not eat orchid seeds. Instead, the wasps must find juicy weevil larvae in which to lay their eggs. When the wasp larvae hatch out, they eat the weevil larvae from the inside out and this is where things get really interesting.

The wasp larvae develop at a much faster rate than do the weevil larvae. As such, they kill the weevil long before it has a chance to eat all of the orchid seeds. By doing so, the wasp has effectively rescued the orchids reproductive effort. Over a five year period, researchers based out of the University of Campinas found that orchid fruits in which wasp larvae have killed off the weevil larvae produced nearly as many seeds as uninfected fruits. As such, the parasitoid wasps have made effective pollinators out of otherwise destructive herbivorous weevils.

The fact that a third party (in this case a parasitic wasp) can change a herbivore into an effective pollinator is quite remarkable to say the least. It reminds us just how little we know about the intricate ways in which species interact and form communities. The authors note that even though pollination in this case represents selfing and thus reduced genetic diversity, it nonetheless increases the reproductive success of an orchid that naturally experiences low pollination rates to begin with. In the hyper diverse and competitive world of Brazilian rainforests, even self-pollination cab be a boost for this orchid.

Photo Credits: [1] [2]

Further Reading: [1]

Parasitic Plant Rediscovered After a 151 Year Absence

Extinction is a hard status to confirm for many types organisms. Whereas discovering a new species requires finding only a single individual, declaring one extinct requires knowing that there are no individuals left at all. This is especially true when organisms live cryptic lifestyles, a point recently made quite apparent by the rediscovery of a small parasitic plant known scientifically ask Thismia neptunis.

Thismia neptunis is a type of parasite called a mycoheterotroph, which means it makes its living by parasitizing mycorrhizal fungi in the soil. It obtains all of its needs in this way. As such, it produces no leaves, no chlorophyll, and really nothing that would readily identify it outright as a plant. All one would ever see of this species are its bizarre flowers that look more like a sea anemone than anything botanical. Like most mycoheterotrophs, when not in flower it lives a subterranean lifestyle.

The original drawing of Thismia neptunis (from Beccari 1878).

This is why finding them can be so difficult. Even when you know where they are supposed to grow, infrequent flowering events can make assessing population numbers extremely difficult. Add to this the fact that Thismia neptunis is only known from a small region of Borneo near Sarawak where it grows in the dense understory of hyperdiverse Dipterocarp forests. It was first found and described back in 1866 but was not seen again for 151 years. To be honest, it is hard to say whether or not most folks were actively searching.

Regardless, after a 151 year absence, a team of botanists recently rediscovered this wonderful little parasite flowering not too far from where it was originally described. Though more study will be needed to flesh out the ecology of this tiny parasitic plant, the team was fortunate enough to witness a few tiny flies flitting around within the flower tube. It could very well be that these odd flowers are pollinated by tiny flies that frequent these shaded forest understories.

As exciting as this rediscovery is, it nonetheless underscores the importance of forest conservation. The fact that no one had seen this plant in over a century speaks volumes about how little we understand the diversity of such biodiverse regions. The rate at which such forests are being cleared means that we are undoubtedly losing countless species that we don't even know exist. Forest conservation is a must. 

Click here to support forest conservation efforts in Borneo. 

Photo Credit and Further Reading: [1]

How a Giant Parasitic Orchid Makes a Living

Photo by mutolisp licensed under CC BY-NC-SA 2.0

Imagine a giant vine with no leaves and no chlorophyll scrambling over decaying wood and branches of a warm tropical forest. As remarkable as that may seem, that is exactly what Erythrorchis altissima is. With stems that can grow to upwards of 10 meters in length, this bizarre orchid from tropical Asia is the largest mycoheterotrophic plant known to science.

Mycoheterotrophs are plants that obtain all of their energy needs by parasitizing fungi. As you can probably imagine, this is an extremely indirect way for a plant to make a living. In most instances, this means the parasitic plants are stealing nutrients from the fungi that were obtained via a partnership with photosynthetic plants in the area. In other words, mycoheterotrophic plants are indirectly stealing from photosynthetic plants.

In the case of E. altissima, this begs the question of where does all of the carbon needed to build a surprising amount of plant come from? Is it parasitizing the mycorrhizal network associated with its photosynthetic neighbors or is it up to something else? These are exactly the sorts of questions a team from Saga University in Japan wanted to answer.

Photo by mutolisp licensed under CC BY-NC-SA 2.0

All orchids require fungal partners for germination and survival. That is one of the main reasons why orchids can be so finicky about where they will grow. Without the fungi, especially in the early years of growth, you simply don't have orchids. The first step in figuring out how this massive parasitic orchid makes its living was to identify what types of fungi it partners with. To do this, the team took root samples and isolated the fungi living within.

By looking at their DNA, the team was able to identify 37 unique fungal taxa associated with this species. Most surprising was that a majority of those fungi were not considered mycorrhizal (though at least one mycorrhizal species was identified). Instead, the vast majority of the fungi associated with with this orchid are involved in wood decay.

Stems climbing on fallen dead wood (a) or on standing living trees (b). A thick and densely branched root clump (c) and thin and elongate roots (d) [Source]

To ensure that these wood decay fungi weren't simply partnering with adult plants, the team decided to test whether or not the wood decay fungi were able to induce germination of E. altissima seeds. In vitro germination trials revealed that not only do these fungi induce seed germination in this orchid, they also fuel the early growth stages of the plant. Further tests also revealed that all of the carbon and nitrogen needs of E. altissima are met by these wood decay fungi.

These results are amazing. It shows that the largest mycoheterotrophic plant we know of lives entirely off of a generalized group of fungi responsible for the breakdown of wood. By parasitizing these fungi, the orchid has gained access to one of the largest pools of carbon (and other nutrients) without having to give anything back in return. It is no wonder then that this orchid is able to reach such epic proportions without having to do any photosynthesizing of its own. What an incredible world we live in!

Photo by mutolisp licensed under CC BY-NC-SA 2.0

Photo Credits: [1] [2]

Further Reading: [1]

On the Ecology of Krameria

Photo by Stan Shebs licensed under CC BY-SA 3.0

There is something satisfying about saying "Krameria." Whereas so many scientific names act as tongue twisters, Krameria rolls of the tongue with a satisfying confidence. What's more, the 18 or so species within this genus are fascinating plants whose lifestyles are as exciting as their overall appearance. Today I would like to give you an overview of these unique parasitic plants.

Commonly known as rhatany, these plants belong to the family Krameriaceae. This is a monotypic clade, containing only the genus Krameria. Historically there has been a bit of confusion as to where these plants fit on the tree of life. Throughout the years, Krameria has been placed in families like Fabaceae and Polygalaceae, however, more recent genetic work suggests it to be unique enough to warrant a family status of its own. 

Regardless of its taxonomic affiliation, Krameria is a wonderfully specialized genus of plants with plenty of offer the biologically curious among us. All 18 species are shrubby, though at least a couple species can sometimes barely qualify as such. They are a Western Hemisphere taxon with species growing native as far south as Paraguay and Chile and as far north as Kansas and Colorado. They generally inhabit dry habitats.

Photo by Stan Shebs licensed under CC BY-SA 3.0

As I briefly mentioned above, most if not all of the 18 species are parasitic in nature. They are what we call "hemiparasites" in that despite stealing from their hosts, they are nonetheless fully capable of photosynthesis. It is interesting to note that no one (from what I have been able to find) has yet been able to raise these plants in captivity without a host. It would seem that despite being able to photosynthesize, these plants are rather specialized parasites. 

That is not to say that they have evolved to live off of a specific host. Far from it actually. A wide array of potential hosts, ranging from annuals to perennials, have been identified. What I find most remarkable about their parasitic lifestyle is the undeniable advantage it gives these shrubs in hot, dry environments. Research has found that despite getting a slow start on growing in spring, the various Krameria species are capable of performing photosynthesis during extremely stressful periods and for a much longer duration than the surrounding vegetation. 

Photo by mlhradio licensed under CC BY-NC 2.0

The reason for this has everything to do with their parasitic lifestyle. Instead of producing a long taproot to reach water reserves deep in the soil, these shrubs invest in a dense layer of lateral roots that spread out in the uppermost layers of soil seeking unsuspecting hosts. When these roots find a plant worth parasitizing, they grow around its roots and begin taking up water and nutrients from them. By doing this, Krameria are not limited by what water or other resources their roots can find in the soil. Instead, they have managed to tap into large reserves that would otherwise be locked away inside the tissues of their neighbors. As such, the Krameria do not have to worry about water stress in the same way that non-parasitic plants do. 

Photo by Stan Shebs licensed under CC BY-SA 3.0

By far the most stunning feature of the genus Krameria are the flowers. Looking at them it is no wonder why they have been associated with legumes and milkworts. They are beautiful and complex structures with a rather specific pollination syndrome. Krameria flowers produce no nectar to speak of. Instead, they have evolved alongside a group of oil-collecting bees in the genus Centris.

One distinguishing feature of Krameria flowers are a pair of waxy glands situated on each side of the ovary. These glands produce oils that female Centris bees require for reproduction. Though Centris bees are not specialized on Krameria flowers, they nonetheless visit them in high numbers. Females alight on the lip and begin scraping off oils from the glands. As they do this, they inevitably come into contact with the stamens and pistil. The female bees don't feed on these oils. Instead, they combine it with pollen and nectar from other plant species into nutrient-rich food packets that they feed to their developing larvae.  

Photo by João Medeiros licensed under CC BY 2.0

Following fertilization, seeds mature inside of spiny capsules. These capsules vary quite a bit in form and are quite useful in species identification. Each spine is usually tipped in backward-facing barbs, making them excellent hitchhikers on the fur and feathers of any animal that comes into contact with them.  

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

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

Are Crickets Dispersing Seeds of Parasitic Plants?

[SOURCE]

Parasitic plants lead unique lifestyles. Many have foregone photosynthesis entirely by living off fungi or their photosynthetic neighbors. Indeed, there are many anatomical and physiological adaptations that are associated with making a living parasitically. Whether they are full parasites or only partial, one thing that many parasitic plants have in common are tiny, dust-like seeds. Their reduced size and thin seed coats are generally associated with wind dispersal, however, there are always exceptions to the rule. Recent evidence has demonstrated that a handful of parasitic plants have evolved in response to a unique seed dispersal agent - camel crickets.

A research team based out of Japan recently published a paper describing a rather intriguing seed dispersal situation involving three species of parasitic plants (Yoania amagiensis - Orchidaceae, Monotropastrum humile - Ericaceae, and Phacellanthus tubiflorus - Orobanchaceae). These are all small, achlorophyllous herbs that either parasitize trees directly through their roots or they parasitize the mycorrhizal fungi associated with said trees. What's more, each of these species are largely inhabitants of the dense, shaded understory of rich forests.

These sorts of habitats don't lend well to wind dispersal. The closed forest canopy and dense understory really limits wind flow. It would appear that these three plant species have found away around this issue. Each of these plants invest in surprisingly fleshy fruits for their parasitic lifestyle. Also, their seeds aren't as dust-like as many of their relatives. They are actually very fleshy. This is odd considering the thin margins many parasitic plants live on. Any sort of investment in costly tissues must have considerable benefits for the plants if they are to successfully get their genes into the next generation.

Fleshy fruits like this are usually associated with a form of animal dispersal called endozoochory. Anyone that has ever found seed-laden bird poop understands how this process works. Still, simply getting an animal to eat your seeds isn't necessarily enough for successful dispersal. Seeds must survive their trip through the gut and come out the other end relatively in tact for the process to work. That is where a bit of close observation came into play.

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[SOURCE]

After hours of observation, the team found that the usual frugivorous suspects such as birds and small mammals showed little to no interest in the fruits of these parasites. Beetles were observed munching on the fruits a bit but the real attention was given by a group of stumpy-looking nocturnal insects collectively referred to as camel crickets. Again, eating the fruits is but one step in the process of successful seed dispersal. The real question was whether or not the seeds of these parasites survived their time inside either of these insect groups. To answer this question, the team employed feeding trials.

They compared seed viability by offering up fruits to beetles and crickets both in the field and back in the lab. Whereas both groups of insects readily consumed the fruits and seeds, only the crickets appeared to offer the greatest chances of a seed surviving the process. Beetles never pooped out viable seeds. The strong mandibles of the beetles fatally damaged the seeds. This was not the case for the camel crickets. Instead, these nocturnal insects frequently pooped out tens to hundreds of healthy, viable seeds. Considering the distances the crickets can travel as well as their propensity for enjoying similar habitats as the plants, this stacks up to potentially be a beneficial interaction. 

The authors are sure to note that these results do not suggest that camel crickets are the sole seed dispersal agents for these plants. Still, the fact that they are effective at moving large amounts of seeds is tantalizing to say the least. Taken together with other evidence such as the fact that the fruits of these plants often give off a fermented odor, which is known to attract camel crickets, the fleshy nature of their fruits and seeds, and the fact that these plants present ripe seed capsules at or near the soil surface suggests that crickets (and potentially other insects) may very well be important factors in the reproductive ecology of these plants.

Coupled with previous evidence of cricket seed dispersal, it would appear that this sort of relationship between plants and crickets is more widespread than we ever imagined. It is interesting to note that relatives of both the plants in this study and the camel crickets occur in both temperate and tropical habitats around the globe. We very well could be overlooking a considerable component of seed dispersal ecology via crickets. Certainly more work is needed.

Photo Credits: [1]

Further Reading: [1] [2]

Parasitic Protection

Strangler figs are remarkable organisms. Germinating in the canopy of another tree, their roots gradually wrap around the host, growing down towards to forest floor. Once in the soil, the interwoven structure of the fig begins to grow and swell. Over time, the strangler fig does what its name suggests, it strangles the host tree. Strangling is bad news for the host, however, new research suggests that strangler figs may actually provide some benefit to larger host trees, at least for part of its life. 

Cyclones are a force to be reckoned with. Their punishing winds can quickly topple even the sturdiest of trees. This is exactly what happened in 2013 when Cyclone Oswald struck Lamington National Park in Australia. Many trees fell victim to this storm but not all. Survival was not random and an interesting pattern started to emerge when researchers began surveying the damage. 

The hollow center of an ancient strangler fig where its host tree once grew and has long since rotted away.  

They found that large trees hosting strangler figs survived the storm whereas those without were more likely to be uprooted. It appears that hosting these parasitic figs just might have some benefits after all. There are a handful of mechanisms with which strangler figs could be helping their hosts. First is that figs spanning multiple trees may provide stability for the host and its neighbors. Another could come in the form of additional leaf area. The canopy of both the fig and its host tree may help reduce the impact of the cyclone winds. Additionally, once they make it to the soil, the roots of the strangler fig may act as guy-wires, keeping the host tree from uprooting. Finally, The interwoven roots of the strangler fig may act as scaffolding, providing additional structural integrity to the host tree. 

More work will be needed to see which of these are the most likely mechanisms. The mere fact that this parasitic relationship might not be so one-sided after all is quite interesting. What's more, by keeping large tree species alive through devastating cyclone events, the figs are essentially keeping legacy trees alive that can then reseed the surrounding forest. This could explain why host trees have not evolved any obvious mechanism to avoid strangler fig infestation. 

Further Reading: [1]

Broomrape: What's in a Name?

Dr. Reuven Jacobsohn, Agricultural Research Organization, Bugwood.org
licensed under a Creative Commons Attribution-Noncommercial 3.0 License.

One can turn a lot of heads by speaking publicly of the plants in the family Orobanchaceae. This interesting and often beautiful parasitic plant family is collectively referred to as the broomrape family. Species with common names like “naked broomrape” and “spiked broomrape” can really make a casual plant conversation turn sour in no time.

Despite how heinous the name sounds, its origin is a bit more innocent. I have really grown to appreciate etymology. Learning the hidden meaning behind the words we utilize for taxonomy can be a lot of fun. It can also teach you a little bit more about the species itself. 

In this context, rape stems from the Latin word “rapum,” which roughly translates to “tuber” or “turnip.” Broom is an English word that, in this context, refers to a shrubby plant related to vetch, which is often parasitized by broomrapes. So, the literal meaning of broomrape is something akin to “broom tuber.” In other words, they are plants growing on the roots of vetch. So, yea, the more you know…

Further Reading: [1]

Photo by Ian Boyd licensed under CC BY-NC 2.0

Photo by Martin Heigan licensed under CC BY-NC-ND 2.0

Photo by Park Ranger licensed under CC BY-NC-SA 2.0

Photo by mpaola_andreoni licensed under CC BY-NC-ND 2.0

A Peculiar Parasite at Berkeley

Parasitic plants are fascinating. I never pass up an opportunity to meet them. On a recent trip to California, my host for the day mentioned that something funny was growing in a patch of ivy on the Berkeley Campus. I had to know what it was. We took a detour from our intended rout and there, growing underneath a pine tree in a dense patch of ivy were these odd purple and brown stalks. This was definitely a parasitic plant.

The plant in question was the ivy broomrape (Orobanche hederae). As both its common and scientific name suggests, it is a parasite on ivy (Hedera spp.). As you can probably guess based on the identity of its host, ivy broomrape is not native to North America. In fact, the population we were looking at is the only known population of this plant you will find in the Americas. How it came to be in that specific location is a bit of a mystery but the proximity to the life sciences building suggests that this introduction might have been intentional. Personally I am quite alright with this introduction as it is parasitizing one of the nastier invasive species on this continent.

The ivy broomrape starts its life as a tiny seed. Upon germination, the tiny embryo sends out a thin thread-like filament that spirals out away from the embryo into the surrounding soils. The filament is looking for the roots of its host. Upon contact with ivy roots, the filament penetrates xylem tissues. The ivy broomrape is now plugged in, receiving all of its water, nutrient, and carbohydrate needs from the ivy. At this point the embryo begins to grow larger, throwing out more and more parasitic roots in the process. These locate more and more ivy roots until the needs of the ivy broomrape are met. Of course, all of this is going on underground.

Only when the ivy broomrape has garnered enough energy to flower will you see this plant. A stalk full of purple tinged, tubular flowers emerges from the ground. At this point its membership in the family Orobanchaceae is readily apparent. Like all members of this family, its parasitic lifestyle is so complete that it is beginning to lose genes for the production of chlorophyll and Rubisco, all things we generally associate with plants. This is why I love parasites so much. Not only are their ecological impacts bewilderingly complex, their evolutionary histories are such a departure from the norm. I will never tire of appreciating such species and I am happy to have met yet another awesome member of this group.

Further Reading:
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1925.tb06671.x/pdf

http://cat.inist.fr/?aModele=afficheN&cpsidt=4107447

Cedar-Apple Rust

Photo by Rocky Houghtby licensed under CC BY 2.0

I have had my eye on these strange brown golf ball shaped growths growing on the twigs of a cedar in my neighborhood for about a year now. I first took notice of them late last spring. They looked pretty nasty but I knew they had to be something interesting. Indeed, “interesting” doesn't even come close to describing their true nature. 

These odd little growths are actually a single stage in the complex life cycle of a group of fungi in the genus Gymnosporangium. Collectively they are referred to as cedar-apple galls. Its a group of fungi whose hosts include junipers and relatives of the apple. Wherever these two lineages coexist you are bound to find this fungus. 

Gymnosporangium exhibit a fascinating life cycle that includes multiple hosts. The golf ball shaped galls will appear on the twigs of a juniper nearly a year after being infected with spores. They grow in size until they reach a point in which they will barely fit in the palm of your hand, though not all reach such proportions. The gall itself is covered in a series of uniform depressions, making it look a little out of place in a natural setting. After a year on a juniper tree, the galls enter into their next stage of development. 

Photo by klm185 licensed under CC BY 2.0

Usually triggered by the first warm rains of spring, strange gelatinous protrusions start to poke out of each depression on the gall's surface. These protrusions continue to swell until the entire gall is covered in bright orange, finger-like masses. These are where the spores are produced. The spores, however, cannot infect another juniper. Instead, they need to land on the next host to complete their life cycle. 

If the spores land on a member of the family Rosaceae (species within the genus Malus are preferred), then the second stage of the life cycle begins. Spores can germinate on both the leaves and the fruit but instead of turning into a large brown gall, they take on a different appearance. This is what makes this fungus readily apparent as a type of rust. A patch of orange will begin to grow. Upon closer inspection one can see that the orange patch is actually a series of small cup-like structures full of spores. 

Come fall, the spores are ready to be dispersed by wind. With any luck, they will land back on a juniper tree and the cycle will start anew. Because of its propensity for apple crops, cedar-apple rust fungi are considered to be a serious pest in apple orchards. In a more natural setting, however, it is a bizarrely unique fungus worth looking for.

Photo Credits: [1] [2]

Further Reading: [1] [2]

Meet Virginia Pennywort

Meet the pennywort gentian (Obolaria virginica). It is a plant of the southeast with its most northerly distribution being around Pennsylvania. I am a little obsessed with gentians so finding this plant is always a special treat. My first encounter left me a bit perplexed by its overall appearance, which is very compact. The leaves and flowers all seemed to be mashed together, competing for space. 

Its small stature and dark coloration cause it to blend in surprisingly well with the forest floor. You often don't see it until you are right on top of one. Something seems to be working well for the Virginia pennywort because once you find one, you usually find many more. Oddly enough, I most frequently see this species in its highest abundance on the side of well-trafficked trails. Add to that its highly reduced leaf area and you have a few traits that usually get me thinking about parasitic plants. Anecdotally speaking, I often find parasitic plants growing near foot traffic. If I had to guess, I would say that it has something to do with root damage, however, I have no data to support such claims. That being said, the literature suggests I wasn't wrong in my suspicions.  

The roots of the Virginia pennywort are described as "coralloid", meaning they take on a structure reminiscent of some corals. This is usually a trait exhibited by species whose roots are closely associated with microbes such as cyanobacteria or certain fungi. Indeed, the roots of the Virginia pennywort are often infested with arbuscular mycorrhizae. Additionally, there is some molecular evidence to suggest that this species is at least partially mycoheterotrophic, meaning it gets some at least some of its nutrients parasitically from said mycorrhizal fungi. Isotope analysis demonstrated that the tissues of the Virginia pennywort were more enriched with isotopes of carbon than the surrounding vegetation.

It is a really neat plant to find. If you do, make sure to take some time with it and get down on its level for a closer look. You won't be disappointed!

Further Reading:
http://www.amjbot.org/content/97/8/1272.short

http://plants.usda.gov/java/profile?symbol=obvi

Newly Discovered Orchid Doesn't Bother With Photosynthesis or Opening Its Flowers

Photo by Suetsugu Kenji [SOURCE]

A new species of orchid has been discovered on the small Japanese island of Kuroshima. Though not readily recognized as an orchid, it nonetheless resides in the tribe Epidendroideae. Although the flowers of its cousins are often quite showy, this orchid produces small brown blooms that never open. What's more, it has evolved a completely parasitic lifestyle. 

The discovery of this species is quite exciting. The flora of Japan has long thought to be well picked over by botanists and ecologists alike. Finding something new is a special event. The discovery was made by Suetsugu Kenji, associate professor at the Kobe University Graduate School of Science. This discovery was made about a year after a previous parasitic plant discovery made on another Japanese island a mere stones throw from Kuroshima.

Coined Gastrodia kuroshimensis, this interesting little parasite flies in the face of what we generally think of when we think of orchids. It is small, drab, and lives out its entire life on the shaded forest floor. Like the rest of its genus, G. kuroshimensis is mycoheterotrophic. It produces no leaves or chlorophyll, living its entire life as a parasite on mycorrhizal fungi underground. This is not necessarily bizarre behavior for orchids (and plants in general). Many different species have adopted this strategy. What was surprising about its discovery is the fact that its flowers never seem to open. 

In botany this is called "cleistogamy." It is largely believed that cleistogamy evolved as both an energy saving and survival strategy. Instead of dumping lots of energy into producing large, showy flowers to attract pollinators, that energy can instead be used for seed production and persistence. Additionally, since the flowers never open, cross pollination cannot occur. The resulting offspring share 100% of their genes with the parent plant. Although this can be seen as a disadvantage, it can also be an advantage when conditions are tough. If the parent plant is adapted to the specific conditions in which it grows, giving 100% of its genes to its offspring means that they too will be wonderfully adapted to the conditions they are born into. 

As you can probably imagine, pure cleistogamy can be quite risky if conditions rapidly change. In the face of continued human pressures and rapid climate change, cleistogamy as a strategy might not be so good. That is one reason why the discovery of this bizarre little orchid is so interesting. Whereas most species that produce cleistogamous flowers also produce "normal" flowesr that open, this species seems to have given up that ability. Thus, G. kuroshimensis offers researchers a window into how and why this reproductive strategy evolved. 

Photo Credit: Suetsugu Kenji

Further Reading: [1]