Saturday, October 31, 2009

The Ghost Plant, a Halloween Appropriate Post

During the Iron Age in Europe, tribes residing in what is the modern day British Isles celebrated the end of summer with a pagan-rooted festival called “Samhain,” which literally translates to “summer’s end” in the Goidelic language used between the 6th and 10th centuries. In conjunction with this festival the Celts believed that the realm of the dead overlapped with the world of the living, and that through divination long dead ancestors could help foretell events of the upcoming year. Samhain is one of many festivals that contributed to the ontogeny of what is now refereed to as Halloween, and like most of the other harvest celebrations it embraced the idea of spirits and ghosts intermingling with the material world. It is in homage to such celebrations of the spirit realm that this post is written; it briefly describes a fascinating plant that has evolved to take on a ghostly appearance and to occupy a unique niche in which it parasitizes parasites, introducing the “ghost plant”.

Due to its eerie appearance and non-typical angiosperm ecology, Monotropa uniflora has been dubbed both the “ghost plant” and the “corpse plan,” though it is also called – less spookily – the “Indian pipe” (undoubtedly because of its ‘uniflora’ which when combined with an elongate stem resembles a smoking pipe). A member of the Ericaceae Family, M. Uniflora is one of about 400 angiosperm species that exhibit an achlorophyllous physiology; they lack chlorophyll and consequently don’t undertake photosynthesis as an energetic process. The lack of chlorophyll is why the plant isn’t green in appearance; rather it displays a white-to-pink hue and exhibits translucence, thus causing it to look like a mushroom or fungus.

Although not a fungus, the ghost plant does take on some fungal-like habits, but before getting to those here are a couple of snapshots of Monotropa uniflora taken earlier this week to serve as a visual aid:

Because Monotropa uniflora doesn’t photosynthesize it doesn’t require sunlight to grow and can even grow in the dark. This ability grants the plant the opportunity to do very well on forests floors which underlay dense canopies that limit the quantity of light penetrating to the herbaceous stratum. The lack of photosynthetic ability means that ghost plant implores a different strategy to acquire and process energy, like many of the fungi that it superficially resembles the plant has adapted to be parasitic.

Not only is the corpse plant a parasite, but even further it is a parasite of parasites! Monotropa uniflora is a myco-heterotroph, this means that it has developed a symbiotic relationship with a fungus. More specifically, M. uniflora parasitizes the ectomycorrhizas (ECM) found on the roots of woody trees.

So, the roots of woody trees (pine, oak, etc…) are parasitized by ECMs, such as members of the Basidiomycota and Ascomycota families and, in turn, these fungi are parasitized by an angiosperm - the ghost plant! These symbiotic relationships can be highly specialized, and in the case of the species Monotropa uniflora Young (et. al.) found that the ghost plant parasitizes members the fungi family Russulaceae specifically.

As another visual aid, here is a photo from the above mentioned research article published in the journal Mycorrhiza showing a Monotropa cluster of hundreds of mycorrhizal root tips from which several achlorophyllous stems (*) are emerging (Reference below).

Because of its spooky appearance, its inclining to parasitism and its poorly illuminated habitat the ghost plant serves as a fascinating example of adaptation and as a fitting topic for a Samhain day blog post.

Young (2002). Monotropa uniflora: morphological and molecular assessment of mycorrhizae retrieved from sites in the Sub-Boreal Spruce biogeoclimatic zone in central British Columbia Mycorrhiza, 12 (2), 75-82

Wednesday, October 28, 2009

Venomous Fables and Phenotypic Variations at the Molecular Level

Remembered for both his lucid writing ability and his tedious nature, the Greek historian Herodotus has often been criticized for the habit of adding unnecessary embellishment to his otherwise candid historical accounts. Focused primarily on the Greco-Persian Wars and personal travels around the Mediterranean, Herodotus’ works also included – on occasion – particulars that many of his 5th Century B.C. contemporaries considered questionable.

One such questionable account from Herodotus centered on the life of a certain Phrygian slave with a knack for composing short prose. Not quite Shakespearian in character, the prose rendered by this slave usually involved references to anthropomorphized wildlife and included a take-home moral message. Now typically, writing prose or verse is a rather benign enterprise, particularly when writing stories about personified animals. Moralizing on the other hand… Moralizing can sometimes get you in trouble, and regrettably for the Phrygian slave, trouble was precisely the result of his high-minded allegories - he was reportedly thrown from a precipice in Delphi for being ugly and “offensive.”

Modern historians raise doubt as to the veracity of Herodotus’ accounts of the Phrygian slave. In fact, many current scholars suspect that the slave never really existed, and further, that the voluminous writings credited to the fictional Phrygian are actually plagiarized collections of Indian folklore. Despite the questionable origins of the parables, the Phrygian slave’s name remains nearly synonymous with “allegory” to this day, and as far as I’m concerned some lessons can still be gleaned from Aesop’s Fables.

One fable in particular came to mind last Wednesday as I was traversing an ecotone between a cypress swamp and a small area of pine flatwoods near Goethe State Forest in central Florida. My eyes being drawn to the rank-and-file procession of hydrophytic plants marching from the wetlands, my ears neglected to notice the slight hum of a rattling creature underfoot. Well, the creature wasn’t quite underfoot; it was in reality about a foot’s distance from being underfoot, but none-the-less the range was sufficiently narrow to take me by surprise. After a couple of second’s pause to regain my bearings, I realized that the insect-like hum that I had heard was in actuality the warning emitted from the shaking tail of the beast – a pygmy rattlesnake!

Pygmy rattlesnakes (Sistrurus miliarius) are members of the Subfamily Crotalinae - the pitviper group - and like their larger Crotalus cousins (true rattlesnakes) the venom of the pygmy contains a toxic cocktail of tissue degrading molecules. Not exactly the kind of critter you want to accidently step on. The potency of the pygmy’s venom is uncontested and is comparable to that produced by other pit-vipers; however the quantity produced by S. miliarius is unlikely to cause death in a human – at least not the death of an adult human. As opposed to human prey, snakes belonging to the Genus Sistrurus have undergone adaptation to capture lizards, small mammals, insects and other snakes as foodstuffs, therefore striking a heavy-footed ecologist would be biting-off more than the snake could chew.

Don’t be misled however, even though the venom of the pygmy is unlikely to cause death, it would certainly pack enough punch to ruin your day; proteins “designed” to enzymaticaly induce hemorrhaging couldn’t be a good thing to have pulsing through your veins… I put the word “designed” in quotes in the previous sentence to emphasize that the protein concoction injected by Sistrurus is very much a product of adaptation - it’s a functional trait shaped by the process of natural selection. But before getting into that story, which will be forthcoming, let me first show you a snapshot of the snake encountered last week and share the Aesop fable that was alluded to above.

The Crow and the Snake
A hungry Crow spied a Snake lying asleep in a sunny spot, and, picking it up in his claws, he was carrying it off to a place where he could make a meal of it without being disturbed, when the Snake reared its head and bit him. It was a poisonous Snake, and the bite was fatal, and the dying Crow said, "What a cruel fate is mine! I thought I had made a lucky find, and it has cost me my life!" (Aesop’s Fables A New Translation by V. S. Vernon Jones, 1912 edition)

The pygmy is still considered a lucky find, though it would have been nice if the picture would have turned out a little better. I could have gotten a bit closer, but ‘as the crow teaches us’ using caution is important and un-scrupulous actions can turn a good scenario into a bad one very quickly… OK, enough with the corny fable, on with the science - before readers encouraged me to follow Aesop over the precipice!

The “designed” venom of Sistrurus… As stated above, the word “designed” refers to a natural process in which variations in phenotype have contributed to differential reproductive success between the individual organisms exhibiting the traits. Specific to this case, the proteins that make-up the hemorrhagic venom are coded for by genes contained within the snake’s genome. Variations in the venom’s genotype from individual to individual cause the overall “potency” of venom to also vary from individual to individual. So, reductively stated, variations in genes coding for venom lead to variations in the “strength” of that venom. The strength of the venom in turn affects the number and quality of prey killed by the snake.

Risking redundancy and stated a third time slightly differently, molecular alterations within the modified saliva of a snake change how those molecules fold and biosynthesize to form the constituent proteins of venom. These phenotypic variations at the molecular level translate to a modified functional trait in the snake’s predator-prey dynamic. Better venom chemistry equals more food, increased survivability and increased fecundity for the snake. Extending the gene’s reach even further, it is conceivable that the molecularly induced change in such a functional trait could even allow the snake to specialize on a certain type of prey, thereby changing its ecology all together.

Interestingly enough, earlier this year H. Lisle Gibbs of Ohio State University, and Stephen P. Mackessy from University of Northern Colorado published work in the journal Toxicon discussing the venom of several Sistrurus species. Their work centered on prey specific effects, and they hypothesized that a “high level of variation in venom at the inter- or intraspecific level allows snakes to specialize on different prey.” They tested the effects of venom on mice, lizards and frogs (typical prey items for Sistrurus) and determined that “toxicity to mammals [was] a major axis along which venom evolution has occurred among Sistrurus rattlesnakes, with little evidence for evolutionary changes in toxicity towards the other prey tested.”

So, the research published in Toxicon demonstrated that not only is the phenotypic functionality of Sistrurus’ venom significant, but also that the response to that venom by prey species may open the door to an evolutionary arms race between predator and prey - an epic battle between toxicity and immunity. Changes in venom chemistry could allow new prey items to be added to the snake’s menu, or conversely, the changes could, in time, ultimately remove current prey species from the carte du jour. Such shifts in dietary preference could easily serve as focal points for selective pressures.

I don’t know if the epic battle between snake venom and prey immunity would stir Herodotus’ interest in war writings, but the story behind the evolutionary dynamic is adequately fascinating to not require very much embellishment. As for me, I’ll take Aesop’s lesson about haste to heart and give greater attention to what’s underfoot.

Gibbs, H., & Mackessy, S. (2009). Functional basis of a molecular adaptation: Prey-specific toxic effects of venom from Sistrurus rattlesnakes Toxicon, 53 (6), 672-679 DOI: 10.1016/j.toxicon.2009.01.034

Sunday, October 25, 2009

Wetland Plant of the Week #30

Osmunda cinnamomea

“Cinnamon Fern”

The cinnamon fern displays clustered leaves with pinnately compound fronds that taper towards their outermost tip. These fronds give O. cinnamomea a similar appearance to that of Woodwardia virginica (Wetland plant of the Week #23), however unlike the chain fern, the base of each cinnamon fern leaflet has a small tuft of orange hair that is visible when the undersides of the fronds are examined - pictured in the last image below.

The fern is not the source of the spice “cinnamon,” rather the cinnamon fern gets its common name from the rusty brown colored (i.e. cinnamon-colored) reproductive structures attached to the specialized (spore-bearing) fronds emerging from the center of the plant – pictured in the image below.

A rhizomatous fern, the roots of O. cinnamomea are highly fibrous, black in color and can grow to form a thickly woven mat as the plant matures. These wiry root masses are often harvested for use as planting substrates in horticulture, which is why the United States Agricultural Service lists the cinnamon fern as commercially exploited here in Florida and as vulnerable in New York State.

The specimen above was photographed last week near Goethe State Forest

Tuesday, October 20, 2009

Connecting Carl Sagan, Richard Feynman and Neil degrasse Tyson

Wow… Carl Sagan, Richard Feynman, Neil deGrasse Tyson and… Bill Nye (?) groove to a music track by John Boswell.

Weird, strange, cool, funny, geeky and nerd-tastic...

There’s another one featuring Hawking at

Monday, October 12, 2009

Wetland Plant of the Week #29

Agalinis purpurea

Purple False Foxglove

One of twelve Agalinis species found in Florida, the purple false foxglove has widely spreading branches, lacks axillary fascicles and displays corollas longer than 2cm.

A Facultative Wet species with geographic distribution over the eastern half of North America, Agalinis purpurea can be found in hydric pine flatwoods, bogs and seepage areas.

These were photographed last week near Aucilla Wildlife Management Area in northwest Florida.

Tuesday, October 6, 2009

Field Photos: Caster canadensis does some landscaping

While doing some fieldwork in north Florida last week, I stumbled across a small duckweed covered pond. This discovery was unexpected…

It was unexpected because, prior to going to field, I had reviewed aerial photos of the area in hopes of identifying any potential wetlands on site – this pond wasn’t on the aerials.

On closer examination of the pond, I noted that several upland species of trees had recently been inundated by the pond and appeared to be in poor condition; it was a new pond and the trees were being overtaken by the water and slowly drowned…

Then I happened onto direct evidence of the crime and suddenly realized the identity of the culprit!

Looking at the scene, I was reminded of Richard Dawkins’s description of beaver-effects in his book The Extended Phenotype.

I guess that the new pond can be viewed as being the result of rodent genes…

At any rate - and despite the ecological renovations shown above - beavers (Caster canadenis) don’t have quite the impact on the landscape down here in the southeastern United States as they do in more northern regions of the Americas. A recent study published to The American Midland Naturalist examined the affects that beavers have on the landscape in southern Georgia – which is less than 90 miles from where the above images were taken in Florida.

What the scientists found was that lower population densities of beaver in the southeast, in conjunction with the year around availability of food, lessened the intensity of beaver induced impacts.

Brzyski, J., & Schulte, B. (2009). Beaver (Castor canadensis) Impacts on Herbaceous and Woody Vegetation in Southeastern Georgia The American Midland Naturalist, 162 (1), 74-86 DOI: 10.1674/0003-0031-162.1.74

Monday, October 5, 2009

Poor Conservation or Good Business?

(This post has been temporarily removed for revision)

Reiss, K., Hernandez, E., & Brown, M. (2009). Evaluation of Permit Success in Wetland Mitigation Banking: A Florida Case Study Wetlands, 29 (3), 907-918 DOI: 10.1672/08-148.1

Sunday, October 4, 2009

Another Tool in the Exobiologist’s Toolbox

In a recent talk at TED, Garik Israelian describes how spectroscopy may help discover life on other planets…

Thursday, October 1, 2009

Frogs and their Metacommunities

In early August, I published a couple of posts discussing the relationship that existed between biphasic animals and the landscape at large. Of particular interest in those write-ups was the way in which organisms – frogs – traversed the landscape and interacted with different ecological communities. The union that the frogs made between distinctly different types of environments was forwarded as an example of “metacommunity”.

Having loosely defined Metacommunities as a set of distinct ecological communities that are biologically entangled through the spatial dispersion of commonly hosted and interacting species, the focal point of those conversations moved to descriptions of some specific behaviors exhibited by spring peeper and squirrel frogs, and how those behaviors could be interpreted through the metacommunity perspective.

To build on those topics, I wanted to recommend a recently found paper that just happens to discuss metacommunities and our previously encountered friend Pseudacris crucifer, the spring peeper.

The paper - Comparative landscape dynamics of two anuran species: climate-driven interaction of local and regional processes - is available here and is free to view and download.

The research details the unique interactions of frogs with the landscape and undertakes an examination of the vernal pools used by peepers and other chorus frogs during reproduction. Of specific focus is the way in which connectivity between breeding sites is maintained during periods of drought and how the frogs respond to such environmental fluctuations. The paper is worth a read as it looks at both the interactions at the local level, and how those local interactions affect ecologies at the scale of a landscape.

My previous posts on the topic can be found here:

To the Woods and Back Again – A Peeper’s Problem

And Here,

The Metacommunity Mannerisms of Foraging Frogs

Werner, E., Relyea, R., Yurewicz, K., Skelly, D., & Davis, C. (2009). Comparative landscape dynamics of two anuran species: climate-driven interaction of local and regional processes Ecological Monographs, 79 (3), 503-521 DOI: 10.1890/08-1047.1