On the Wood Rose and its Bats

Photo via Nga Manu Nature Reserve

New Zealand has some weird nature. It is amazing to see what an island free of any major terrestrial predators can produce. Unfortunately, ever since humans found their way to this unique island, the ecology has suffered. One of the most unique plant and animal interactions in the world can be found on this archipelago but for how much longer is the question.

The story starts with a species of bat. In fact, this bat is New Zealand's only native terrestrial mammal. That's right, I said terrestrial. The New Zealand lesser short-tailed bat spends roughly 40% of its time foraging for insects on the ground. It has lots of specialized adaptations that I won't go into here but the cool part is they forage in packs, stirring up insects from the leaf litter until they reach a level of feeding frenzy that I thought was only reserved for sharks or piranhas. Along with using echo location, they also have a highly developed sense of smell. This is important for our second player in this forest floor drama.

Enter Dactylanthus taylorii, the wood rose. This plant is not a rose at all but rather a member of the tropical family Balanophoraceae. More importantly, it is parasitic. It produces no chlorophyll and lives most of its life wrapped around the roots of its host tree underground. Every once in a while a small patch of flowers break through the dirt and just barely peak above the leaf litter. This give this species it's Māori name of "pua o te reinga" or "pua reinga", which translates to "flower of the underworld." The flowers emit a musky, sweet smell that attracts these ground foraging bats. The bats are one of the only pollinators left on the island. They sniff out the flowers and dine on the nectar, all the while being dusted with pollen. Recently, it has been found that New Zealand's giant ground parrot, the kakapo, is also believed to have been a pollinator of this plant. Sadly, today the kakapo exists solely on one small island of the New Zealand archipelago.

Both the wood rose and the New Zealand lesser short-tailed bat are considered at risk for extinction. When modern man came to these islands they brought with them the general suite of mammalian invasives like rats, mongoose, cats, and pigs, which are exacting a major toll on the local ecology. The plants and animals native to New Zealand have not shared an evolutionary history with such aggressive mammalian invaders and thus have no adaptations for coping with their sudden presence. The future of the wood rose, the New Zealand lesser short-tailed bat, and the kakapo, along with many other uniquely New Zealand species are for now uncertain.

Photo Credits: Joseph Dalton Hooker (1859) and Nga Manu Nature Reserve (http://www.ngamanu.co.nz/)

Further Reading:

http://bit.ly/2bBw8FT

http://bit.ly/2bKRY90

http://bit.ly/2bKpxfE

Buffalonut - A Parasitic Shrub From Appalachia

I have a hard time with shrubby species. They just don't stand out to me like herbaceous plants or giant trees. As such, my identification skills for this group of medium-sized woody plants are subpar. However, every once in a while I find something that I can't let go. Usually its a species with a trait that really stands out. This is how I came to know buffalo nut (Pyrularia pubera). Its unique inflorescence was like nothing I had ever encountered before. 

There is good reason for my unfamiliarity with this species. It is largely restricted to the core of the Appalachian Mountains, although there are records of it growing on Long Island as well. Regardless, it is not a species I grew up around. The first time I saw its flowers I was stumped. I simply couldn't place it. Luckily its unique appearance made it easy to track down. I was happy with buffalo nut for the time being but I was surprised yet again when I sat down for a chat with someone who knows woody species much better than I do. 

As it turns out, buffalo nut belongs to the sandalwood family, Santalaceae. This makes it a distant cousin of the mistletoes. Like most members of this family, buffalo nut lives a parasitic lifestyle. Although it is fully capable of photosynthesis and "normal" root behavior, under natural conditions, it parasitizes the roots of other tree species. It doesn't really seem to have a preference either. Over 60 different species hailing from 31 different families have been recorded as hosts. 

When a buffalo nut seed germinates, it starts by throwing down a taproot. Once the taproot reaches a certain depth, lateral roots are sent out in search of a host. These roots "sniff out" the roots of other species by honing in on root exudates. When a suitable root is found, the buffalo nut root will tap into its host using specialized cells called haustoria. Once connected, it begins stealing water and nutrients. Buffalo nut roots have been known to travel distances of 40 feet in search of a host, which is pretty incredible if you ask me. 

It is easy to look down on parasites. Heck, they are largely maligned as free loaders. This could not be farther from the truth. Parasites are a healthy component of every ecosystem on the planet. They are a yet another player in a system that is constantly changing. What's more, the presence of parasites can actually increase biodiversity in a system by keeping certain species from becoming too dominant. Buffalo nut should not be persecuted. Instead it should be celebrated. It is yet another species that makes the Appalachian Mountain flora so unique. 

Further Reading: [1] [2]

A Fern With Flower Genes - An Odd Case of Horizontal Gene Transfer

Photo by Aaron Carlson licensed under CC BY-SA 2.0

When researchers at Harvard decided to take a look at the genome of the rattlesnake fern (Botrypus virginianum) they found something completely unexpected. Whereas one set of genes they looked at placed this species firmly in the family to which it belongs, Ophioglossaceae, two other genes placed it in the Loranthaceae, a completely unrelated family of flowering plants. What are flowering plant genes doing in a fern?

The rattlesnake fern is a ubiquitous species found throughout the northern hemisphere. It is believed to have evolved in Asia and then radiated outward using ancient land bridges that once connected the continents. At some point before this radiation occurred, the rattlesnake fern picked up some genes that were entirely foreign.

Horizontal gene transfer, the transfer of genes from one organism to another without reproduction, is nothing new in nature. Bacteria do it all the time. Even plants dabble in it every now and then. The surprising thing about this recently documented case is that it is the first discovery of horizontal gene transfer between an angiosperm and a fern. Up until this point, examples within the plant realm have been seen between ferns and hornworts as well as some parasitic plants and their hosts.

This is why the rattlesnake fern genome is so interesting. How did this occur? Though there is no way of telling for sure, researchers believe that one of two things could have happened. The first involves root parasitism. The family Loranthaceae is home to the mistletoes, a group of plants most famous for their parasitic nature. Although the majority of mistletoe species are stem parasites, at least three genera utilize root parasitism. It could be that an ancient species of mistletoe transferred some genes while parasitizing a rattlesnake fern.

This scenario seems to be the least likely of the two as no representatives of the root parasitic mistletoes currently exist in Asia, though it is entirely possible that some did at one time. The other possibility doesn't involve parasitism at all but rather fungi. Rattlesnake ferns are obligate mycotrophs and thus cannot live without certain species of mycorrhizal fungi. Perhaps the transfer of genes was achieved indirectly via a shared mycorrhizal network. This hypothesis is especially tantalizing because if it is found to be true, it would help explain many other examples of horizontal gene transfer that currently lack a mechanism. Only time and more research will tell.

Photo Credit: Aaron Carlson (http://bit.ly/1OAVhNZ)

Further Reading:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560187/

Feed Me, Seymour!

Photo by Ebony Black Public Domain

In the spirit of spooky-ness, today I would like to introduce you to some of the most bizarre looking plants on our planet. I am of course talking about the genus Hydnora. Known locally as jakkalskos (jackal food) or bobbejaankos (baboon food), these odd parasites certainly look creepy. However, their ecology is downright fascinating and well worth a closer look.

Hydnora comprises roughly seven species and currently resides in its own family, Hydnoraceae. More recent taxonomic work suggests that this may actually be a subgroup within the family Aristolochiaceae, but as far as I know, the jury is still out on this. All species are native to southern Africa and as you can probably tell from the picture, they produce no leaves and no chlorophyll. Instead of wasting energy on producing its own food, Hydnora has resorted to parasitism. They are root parasites on members of the family Euphorbiaceae. They tap into the roots of their host plants using specialized structures called "haustoria." In this way they are able to gather all their nutritional needs from their host. Once a Hydnora has obtained enough energy it will produce a flower.

The flower is all you will ever see of this plant. The strange, scaly structure emerges from the ground underneath its host. Three slits begin to form, each lined with white, hair-like structures. At first these structures remain intact. The spaces between are just big enough to allow entry of pollinators, which in this case are dung beetles. Once the flower opens these slits it begins to produce some heat, not unlike what we see in many aroids. The heat helps to spread the scent and the smell is what you would expect from a plant trying to attract dung beetles - it smells like feces.

Photo by Charles Stirton licensed under CC BY-NC-ND 2.0

When a dung beetle arrives looking for some fresh poop, it enters the flower through those slits and falls down into the trap. The rest of the flower consists of a tube-like structure underground. To keep the beetles from escaping, Hydnora employs a trick used by many carnivorous pitcher plants. Lining the walls are downward pointing hairs that prevent the beetles from crawling out before their job is done. Once inside, the beetles are drawn to the center where the smell is emitted. Here they are dusted with generous amounts of pollen. If the beetles have arrived after a previous Hydnora visit then they will also deposit pollen and thus reproduction is achieved. Once the plant releases pollen onto the beetles, the hairs lining the wall relax and the slits open completely, allowing the beetles to escape.

I hope some day to see one of these in person. To the best of my knowledge, only a single species (Hydnora africana) has ever been grown in cultivation and that was a single event. Seeds were sown in a pot containing a known host species of Euphorbia. It took a very long time for germination and even longer to mature and produce a flower. Either way this creepy species is actually quite fascinating.

Photo Credit: [1] [2]

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

On Parasites and Diversity

Photo by Sannse licensed under CC BY-SA 3.0

We all too readily demonize parasites. It is kind of understandable though. The thought of something living in or on you at your expense is enough to make our skin crawl. There are a lot of evolutionary pressures that make us look unfavorably about organisms with such lifestyles. However, to completely write parasites off as a bane to life as we know it may be a huge mistake on our part. More and more we are realizing that parasites play an important role in ecosystem functioning and may even serve as indicators of environmental health. 

Plants are no stranger to such parasitic dynamics. Many species have forgone some if not all photosynthetic ability in exchange for a parasitic lifestyle. There is no question that plant parasites can and do have net negative effects on their hosts, however, its never that simple. Research is showing that parasitic plants can have profound effects on the structure and productivity of surrounding plant communities. 

For starters, parasitic plants can increase the competitive ability of non-host species. By knocking back the performance of their host, other plant species can pick up the slack so-to-speak. This can often lead to an increase in overall plant diversity in a given habitat. A common thread throughout studies that have looked at parasitic plants is that proportion of grasses declined when parasitic plants were present. This made room for less competitive forbs to increase in number. In effect, parasitic plants can level the playing field for other, less competitive plant species. 

By altering ecosystem structure, parasitic plants can also alter the way nutrients flow through the system. This can have some seriously profound ramifications. For instance, the presence of the hemiparasitic Rhinanthus minor in grasslands has been shown to  increasing rates of nitrogen cycling. Though the ramifications of this are dynamic, it is nonetheless proof that parasites should not simply be maligned and that, despite our perspective, nature is far more complex than we realize. 

Photo Credit: Sannse (Wikimedia Commons)

Further Reading:

http://www.nature.com/nature/journal/v439/n7079/full/nature04197.html#B10

http://link.springer.com/article/10.1007%2FBF00319016

http://www.sciencedirect.com/science/article/pii/S0006320797000104

http://www.jstor.org/stable/10.1086/303294

Euphrasia

Meet Euphrasia nemorosa, the eyebright. This lovely little plant is native to the northern regions of North America. A quick glance at the flowers of this species may seem to suggest a member of the mint family but this would be wrong. Once placed in Scrophulariaceae, it is now thought to reside in Orobanchaceae. Like other members of this group, E. nemorosa is a hemiparasite. It uses specialized roots to tap into the roots of plants growing around it. In the wild, research has shown that E. nemorosa seems to prefer to parasitize grasses but laboratory experiments have shown that it will parasitize a variety of plants if given the chance. It can even grow without parasitizing other plants but those that did grew small and weak. 

Parasitic plants are an interesting bunch. They push the limits of what is traditionally accepted in the realm of plant physiology. Non-parasitic plants usually have to balance between CO2 uptake and water loss. They do this by controlling their stomata, which are tiny openings on the leaf. Because they are attached to a host, parasitic plants do not have to worry about minimizing water loss and instead want to maximize water loss to gain as much carbon from their host plant as possible. 

Another interesting aspect of Euphrasia ecology is their preference for disturbance. Euphrasia are plants of disturbed meadows, fields, and man-made habitats. There is a lot of work being done to examine which kinds of species thrive in and around humans. Research has shown that by selecting for native species like Euphrasia, the species composition on these types of disturbed habitats can take on a more biodiverse character instead of the usual non-native monoculture.

Further Reading:
https://gobotany.newenglandwild.org/species/euphrasia/nemorosa/

http://www.archive.bsbi.org.uk/Wats6p1.pdf

http://jxb.oxfordjournals.org/content/39/8/1009.short

http://www.archive.bsbi.org.uk/Wats5p11.pdf

Scarlet Paintbrush

Roadways have been surprising me quite a bit as of late. Where I live, they are havens for aggressive invaders such as crown vetch (Securigera varia), sweet pea (Lathyrus odoratus), and a seemingly endless variety of turf grasses. However, this does not seem to be a pattern that repeats itself everywhere. More and more I have come to notice that roadsides in other locations harbor a wide variety of native plant life, some of which are downright surprising.

My most recent foray into Canada revealed some surprising roadside botany. While cruising down a highway, my friends and I began noticing bright red dots spread about the shoulders of the road. The red was so bright it was impossible to ignore. We had to find out the source. Within a few steps we soon realized where the color was coming from. It was none other than the scarlet paintbrush (Castilleja coccinea).

Needless to say, I was beyond excited. I have tried for years to grow this plant, which is endangered in the state of New York. All of my attempts have been met with failure so finally getting a chance to see this species was a momentous occasion. Like all others in this genus, C. coccinea is a hemiparasite. Using specialized roots it taps into the roots of neighboring plants and steals nutrients. Research has shown that C. coccinea doesn't seem to be too picky as to which plants it parasitizes, though it is likely that some plants are better hosts than others.

The plight of this species extends far beyond my home state. Native to much of eastern North America, this lovely species has been all but eradicated from the New England states. The most common reason for this is habitat destruction. We simply love to develop and farm the kinds of places that C. coccinea grows.

Another serious but less obvious threat to C. coccinea is succession. As is typical of our species, we tend to manage the land in a feast or famine sort of way. Its either total destruction or an adherence to an often false ideal centered around the word "pristine." A lack of disturbance is great for some species but spells disaster for others. Thus, as woody species, especially invasives such as multiflora rose (Rosa multiflora), encroach into open habitat, plants that cannot handle shading such as C. coccinea quickly disappear from the landscape. This is a species that requires some disturbance to survive. Land managers and stake holders would do good by paying attention to the habitat requirements of such species.

Further Reading:
http://www.newfs.org/docs/pdf/Castillejacoccinea.pdf
http://www.jstor.org/stable/2483296…
http://plants.usda.gov/core/profile?symbol=caco17

An Aromatic Parasite

What smells like honey and parasitizes fungi? Why, Monotropa hypopitys of course! Its specific epithet gives you an idea of where you may stumble across one of these strange beauties. Hypo means under and pitys means pines. It is no wonder then that the common name of this species is "pinesap."

I love parasitic plants and to find this species was a real excitement. I smelled it before I saw it. The yellowish coloration of this specimen represents the norm, however, individuals with a more reddish hue are not unheard of. Pinesap has a distribution spanning the forests of the northern hemisphere. It is the most widely distributed member of the genus. Despite this fact, stumbling across a population is a relatively rare occurrence.

Pinesap falls under the category of mycoheterotroph. It parasitizes fungi, specifically those in the genus Tricholoma. As such, it is an indirect parasite of trees, taking nutrients that the fungi obtained from the trees they associate with. The relationship between pinesap and its associate fungi are rather specific. The structures they form are so unique that researchers have created a new term just to describe it - 'monotropoid’.

For most of its life, pinesap lives underground as a collection of highly specialized roots. Come early summer, individuals with enough stored energy will throw up what looks like a stem covered in flowers. In actuality, pinesap does not produce anything that could be called a true stem. Instead, the structure we see is actually an inflorescence called a raceme.

As mentioned above, the flowers have a scent that reminds me of spicy honey. Bees are the main visitors of the flowers, though most researchers feel that the plant mainly self pollinates. It has been observed that yellow individuals tend to flower earlier in the summer while red individuals tend to flower closer to fall. Whether this is any indication that these are separate subspecies remains to be seen. Recent genetic analysis suggests that pinesap may very well deserve its on genus, Hypopitys monotropa. More work needs to be done to figure out if it is deserved.

Further Reading:

http://www.fs.fed.us/wildflowers/beauty/mycotrophic/monotropa_hypopitys.shtml

Rusty Mustards

Believe it or not, what you are seeing here is the same species of plant. The one on the left is the normal reproductive state of a Boechera (Arabis) mustard while the one on the right is the same species of mustard that has been infected by a rust fungus known as Puccinia monoica.

The interaction of these two species is interesting on so many levels. I spent an entire summer, along with my botanical colleagues, completely stumped as to what this strange orange-colored plant could be only to eventually find out that it was a mustard that has been hijacked! The fungus in question, P. monoica, is part of a large complex of interrelated rust fungi who are quite fond of mustards. The reason for this all boils down to reproduction.

The lifecycle of P. monoica begins when spores land on a young mustard plant and invade the host tissue. As they grow, they gain more and more nutrients from the mustard. Eventually the fungi effectively sterilizes the mustard and causes it to begin forming what are referred to as "pseudoflowers." The pseudoflowers are basically leaves that have been mutated by the fungus to look and smell a lot like other plants blooming in early summer.

The pseudoflowers produce a sticky, nectar-like substance that is very attractive to pollinators. The mimicry even goes as far as to produce yellowish pigments that reflect UV light, making them an even more irrisistable target for passing insects. On each pseudoflower are hundreds of small cups known as spermatogonia. These house the sex cells of the fungus. Visiting insects get covered in these sex cells, which they will then transfers to other infected plants thus achieving sexual reproduction for the fungus.

Still with me?

At this point, the pseudoflowers stop producing color and nectar and instead, the fused sex cells germinate into hyphae that begin to form specialized structures called "aecia." The aceia house the spores that will be responsible for infecting their secondary host plants, which are grasses. Spores blow about on the wind and, with a little luck, a few will land on a blade of grass. The spores germinate and infect the grass. From there, structures called "uredia" are formed that go on to produce even more spores to infect even more grass. Eventually, structures called "telia" are formed on the grass and the cycle finally comes full circle. The telia produce the spores that will go on to infect the original mustard host plants.

Whew! To have stumbled across an evolutionary drama such as this serves as a reminder of just how much in nature goes largely unnoticed every day.  

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

An Extinction in Chicago

Chicago may seem like a strange place for the last stronghold of a plant species, however, that was the case back in 1916. In 1912, a graduate student by the name of Norma Pfeiffer was exploring a wet prairie near Torrence Avenue in Chicago when she stumbled across something peculiar. What she found had completely stumped the botany department. Her description of this little mystery ended up earning her a Ph.D.

What she had discovered was indeed a plant, but it was like nothing else known in this region. The plant was named Thismia americana. T. americana, like all member of the Burmanniaceae family, is a mycoheterotroph. It made its living by parasitizing mycorrhizal fungi in the soil. Because of this lifestyle, T. americana did not bother with leaves or even chlorophyll. It simply stored up enough energy to produce its tiny translucent white and blue-green striped little flower, which barely breached the soil surface.

The oddest thing about finding a Thismia growing in Illinois (let alone in Chicago) is that the family with which this plant belonged is very much tropical in its distribution. Its closest living relatives grow only in Australia, New Zealand, and Tasmania (the color picture below). What was this odd little species doing in northern North America? Pfeiffer continued to encounter and examine these plants for another 5 years after her initial discovery. Sadly, 1916 was the last year that anyone ever saw these plants again. The site in which the original population was found has since been developed.

Photo by Tindo2 - Tim Rudman licensed under CC BY-NC 2.0

There have been many repeated attempts at rediscovering this species. In 1949, Pfeiffer herself worked with a team of botanists in an attempt to find new populations of T. americana. They were unsuccessful. Another search was launched in the early 1990's. Volunteers were given pictures and models of the plant in hopes that they could develop a search image. They were also tested using small bluish-white beads scattered around prairie vegetation to see if they were even capable of finding a flower as small as T. americana's. Just as in 1949, no Thismia were found (nor were most of the beads apparently) though the team did turn up at least 17 plant species never recorded in that region before. Their time was not wasted. Similar searches in 2002 and 2011 have produced similarly disappointing results.

How and why this species came to be part of the prairies of Illinois will forever remain a mystery. Many have tried to find it since. All have failed. Some still hold out hope that a small remnant population remains somewhere hidden beneath goldenrods and various grasses. Given the size and appearance it is easy to see how such a plant could be overlooked. If anything, Thismia americana stands as a reminder of how important even the smallest nature preserves can be. For species like this, the simple act of preserving a chunk of land smaller than a city block could have made all the difference.

Photo Credit: Tindo2 (http://bit.ly/1wmHiWu), Mark Mohlenbrock and http://www.chicagowilderness.org

Further Reading:
http://www.jstor.org/stable/2468713…

http://www.jstor.org/stable/2469255…

http://www.jstor.org/discover/10.1086/674315…

http://www.chicagowilderness.org/…/…/summer2004/thismia.html

Sandfood

Photo by USFWS Pacific Southwest Region licensed under CC BY 2.0

Photo by Don Davis licensed under CC BY-NC-ND 2.0

Pholisma is yet another amazing genus of parasitic plants. Endemic to the southwestern United States and Mexico, these peculiar members of the borage family tap into the roots of a variety of plant species. They do not photosynthesize and therefore obtain all the nutrients they need from their hosts. Oddly enough, researchers have found that most of their water needs are met by absorbing dew through the stomata on their highly reduced, scale-like leaves. Water is then stored in their highly succulent stems. Throughout their limited range, Pholisma are critically imperiled. Development and agriculture have already eliminated many populations. To add insult to injury, the dunes in which most extant populations are found are owned by the BLM and are open to heavy off-road ATV traffic, which will likely push them to the brink of extinction if nothing is done to limit such recreational use. Unless people speak up about protecting these plants and their habitats, they could disappear for good.

Photo by Vijay Somalinga licensed under CC BY-NC-ND 2.0

Photo by Vahe Martirosyan licensed under CC BY-SA 2.0

Photo Credits: [1] [2] [3]

Further Reading: [1] [2]

The Truth About Mistletoe

While perusing a local indie market this weekend I noticed that there was a stand selling mistletoe branches. It was odd to note that, for as ubiquitous of a symbol it is during this time of year, so few people realize what these plants are all about.

A reference to mistletoe could be any number of plants in the order Santalales. It is a large and rather varied grouping but the common thread throughout Santalales is parasitism on some level. Many species grow in the form of a shrub that grows epiphytically and taps into a host tree. While most still undergo photosynthesis, they also obtain nutriment using specialized structures that plug into the vascular tissue of their host. If infestations are intense enough, mistletoe can kill a tree.

However, don't let this fact leave you with any animosity toward mistletoe. Far from being a drain on the ecosystem, evidence is showing that many mistletoe species are keystone organisms where they are native. They produce copious amounts of berries that attract and feed a wide variety of birds and their growth habit makes for great nesting sites as well. Their leaves and shoots are munched on by a multitude of insect life, which then attracts animals higher up the food chain. Because of the preponderance of bird species that frequent mistletoe, other berry producing plants in the area benefit as well. In one study, researchers found that junipers had higher rates of reproduction when growing near mistletoe. Because mistletoe attracts all of those berry eating birds, numbers of seed carriers significantly increase for all other berry producing plants.

The most commonly encountered species of mistletoe is probably Viscum album. This evergreen species ranges from north Africa to southern England all the way to parts of Asia. It is evergreen and seems to really like growing on apple trees (Malus sp.). My favorite thing about this species as well as many other mistletoe is how they manage to reproduce. As mentioned above, they produce plump berries that birds can't resist. The pulp of the berry is quite sticky and thick that when the bird digests what it can and voids the rest, it has to wipe itself on a branch. This causes the mistletoe seed to stick to the branch like glue. When the seed germinates it attaches itself to the tree, living independently at first but later tapping into the trees vascular tissue. Next time you pucker up with someone special under one of these plants, keep that in the back of your mind!

Photo Credit: Martin LaBar

Further Reading: 
http://www.kew.org/plants-fungi/Viscum-album.htm

http://www.annualreviews.org/doi/abs/10.1146/annurev.ecolsys.32.081501.114024

http://onlinelibrary.wiley.com/doi/10.2307/4013039/abstract