Sunday, December 27, 2009

Festuca paradoxa and why we know we know nothing

The mention of fescue often brings to mind tough, stringy, silica-laden strands of grass being pulverized by the broad molars of cattle, cudding its way through the four steamy stomachs of the beast only to be expelled in a watery, brownish-green ooze of hot acrid defecation upon an overgrazed, cracked and sore, field that once harbored an intricate assemblage of native organisms but that is now reduced to a monoculture of fescue. Or at least it does to me. But there are good fescues in the world. Ones whose histories are not synonymous with the death knell of Midwestern natural systems. Folks with a remedial knowledge of Midwestern natural communities are aware of Festuca subverticillata (Nodding Fescue); a native species commonly found in woodlands and forests of decent remnant natural integrity. Others might be surprised to know there is another native fescue in our midst. I am writing, of course, of Festuca paradoxa.

Festuca paradoxa resembles F. subverticillata in gross morphology but is generally larger and occurs in more open habitat. Here is mediocre photo of the overall habit of F. paradoxa:
Festuca paradoxa also has more spikelets on the lower branches of the inflorescence than F. subverticillata (8-20 vs. 2-7).
Both of the afore mentioned native species can be differentiated from the exotic F. arundinacea (aka F. elatior, Schedonorus arundinaceus and S. phoenix) by having leaves that are distributed evenly along the stem (basal distributed in F. arundinacea) and by lacking finely ciliate auricles.

The spikelets of F. paradoxa (below) are very typical of fescue wherein the glumes are about as long as the lemmas which are elliptic in outline with acuminate tips. Members of the genus Festuca typically have fewer florets per spikelet (3 to 10) than grasses with a similar morphology.
To the field botanist, who relies heavily on the vegetative characters of grasses for identification, fescue venation is quite distinct. The adaxial leaf surface has many raised nerves which give it the texture and appearance of a vinyl record.
The auricle of F. paradoxa is creamy white in coloration and contrasts with the yellow-green of the leaf blade and sheath.
The auricle of F. subverticillata is green or sometimes tinged with purple, while the auricle of F. arundinacea (below) has a pronounced yellowish coloration in stark contrast to the dark green of the blade (note the ciliate margins which are indicative of F. arundinacea).
Festuca paradoxa is a bit of an enigma. Geographically, it occurs in the eastern regions of the Great Plains states (Texas, Kansas, Nebraska….), east to Pennsylvania and Georgia and north to Minnesota and Wisconsin. However outside the east-central portions of the Tallgrass Prairie Ecoregion and the Ozarks, its distribution is very spotty. It is listed as a species of conservation concern in ten states and potentially extripated from three. On a county by county basis, Missouri has the most occurrences of F. paradoxa, but even here it is rarely encountered. When it is encountered one usually finds but a few stems or a single patch in areas where suitable habitat abounds. Why?

(WARNING: the following is theoretical ramble based on general assumptions and oversimplifications serving ultimately to illustrate a point that the author concedes may itself be an overgeneralization of the facts).

In any given flora there are species whose occurrences within the landscape are infrequent and seemingly patternless. These plants exemplify the difficulty inherent to our human understanding of the structural, temporal and compositional complexity of natural systems; the plethora of biotic and abiotic influences over the evolutionary histories of species as they assemble into natural communities and disassemble as influences change. In most cases the ranges of species are either expanding or contracting depending on the abundance of suitable habitat and their ability to disperse into said habitat; where suitable habitat is defined as the proper biotic and abiotic conditions necessary to colonize, persist and reproduce. Climate change (non-human induced, for these purposes) is one of the larger factors involved in the ebb and flow of the geographical ranges of species. As the availability of suitable habitat decreases in a region, species become isolated in the fragments of habitat. Pleistocene relict species are classic examples of this phenomenon. Such relicts are usually edge of range species associated with regionally rare habitats. Other major factors include a missing pollinator or seed disperser which can ultimately result in a fragmented range but usually is not primarily associated with a fragmented habitat. In this case, plenty of habitat exists but the species does not seem to be able to colonize it successfully. Of course, all of this is further complicated by the fact that subtle changes in climate or the achieved evolutionary potential of competitors, predators or symbionts can lead to local or global extinctions.

But how does this relate to F. paradoxa? Ultimately, all that can be said is that because it is found in small, isolated populations across its range despite the availability of seemingly suitable habitat it best fits the pattern of a species with a contracting/fragmenting distribution. As is the case for many such species with similar distributions, this is where our knowledge runs out of gas. Such scenarios illustrate the ignorance of science as it relates to a functional understanding of individual species; as such knowledge relates to the reality of species distributions. Yet outside the realm of federally threatened species you never hear botanist discussing these strange distributions. Which make me wonder how can we protect potentially imperiled species or manage natural communities with nothing more than a basic understanding of regional phytogeography?

Here is good example of what I am talking about. A few years ago I collected data pertaining to the herbaceous and woody ground flora in several natural areas in the Chicago region. The research was directed at demonstrating the effects of deer browse. These preserves were being managed as black oak savannas and each had numerous acres of very large trees most of which were black oaks (Quercus velutina). Land surveyor notes as well as the matrix flora of these sites verified that these sites were likely black oak savannas historically. While collecting quadrat level data throughout the region at these flagship preserves we started noticing that several of the sites had no oak seedlings in the understory. We then noticed that there were no oak saplings, nor any young trees. None. Just large 150 to 300 year old oak trees. When we brought it up to the scientist in charge we were met with blank stares and some on-the-fly explanation the boils down to a “burn it and they will come” philosophy. A more likely explanation, based on my own speculation, is that these sites have been changed such that they no longer favor black oak colonization even though there are tons of acorns raining into the seed pool annually. These sites were heavily grazed for over a century. It seems likely that anything ranging from soil compaction to changes in mycorrhizal interactions (little is known about invasive/exotic soil fungi) could have killed these savannas decades ago in terms of population structure. The situation is akin to visiting a retirement home, not noticing the disproportionate number of elderly people and instead convincing ourselves that they have the potential to be a flourishing community if we can only rehabilitate them. I fear such ignorance is rampant when dealing with floristic shift that take decades, centuries or even millennia to unfold.

This brings us back to F. paradoxa and species like it whose distributions we can’t explain or worse, that no one is trying to explain. If we are to successfully preserve, restore or, god forbid, recreate natural systems, we should be able to answer questions regarding species assemblages. Otherwise we are practicing science based on blind-guesses and the active application of assumptions about past systems that may or may not apply to current scenarios. It seems to boil down to the Socratic Paradox in that “All we know, is that we know nothing”.
So the next time you encounter F. paradoxa, waving gracefully in the breeze, admire its current station in the modern landscape and remember to ponder what missing pieces of the puzzle it could provide if we only knew the relevant questions.

Wednesday, December 2, 2009

The Board

One of the best classes I took as an undergraduate was Plant Taxonomy. Not just because I drool over the topic, but because the professor, Dr. Robin Kennedy, taught it with great enthusiasm. She also developed a wonderful structure for the class; lab and lecture. Our exams were a mix of live and pressed plant specimens that we had to identify by their visible characters. We were also given lists of characters to which we had to match families. For example, what family has tetradynamous stamens? Why, Brassicaceae, of course. We covered over 60 families of vascular plants over the semester and the mental organization of information for all these families, their characters, associated terminology and their floral formulae was mind melting. However, we were given a tool.

In the first lab session we were handed a manila file folder which we placed on a light board and upon it we traced a series of rows and columns. Each column was given a heading like “United Carpels” or “Zygomorphic”. As the weeks passed and we learned what these terms meant, we added each new family to its corresponding column by copying the information off a large blackboard at the corner of the room. It was called “The Board”.


I spent hours memorizing The Board, or at least my copy of it. When lab exams began, I would quickly draw it on the back of my exam and write in all the families. Years later, I occasionally whip out The Board for a quick refresher. I relearn such fun facts as Solanaceae has a superior ovary and Malvaceae has monodelphous stamens. Then I fold it up and stuff it back into my plant tax book.

I ran across The Board the other day. I hadn’t reviewed it for quite a while and I was embarrassed by how little plant family trivia I could recall. I decided to breathe new life into The Board by typing it into a spreadsheet and posting it on my office wall. As I once again added each family to the rows and columns I decided it would be fun to add more families of angiosperms. That done and still enjoying the process, I turned to the fern families which have always troubled me since I never had to learn them. So I added them too. After several sessions and more hours than I care to admit The Board seemed to have reached its full potential. I liked the finished product so much that I thought I would share it. Here it is (click photo to enlarge):

Here’s how it works. First, everything in the black-lined corner on the bottom left is a non-angiosperm family or a monocot. The rest are dicot angiosperms. To derive at a single family, start at the top and follow the appropriate column until you reach a list of families. Then you need to examine the list for characters that best fit the plant you may be identifying.

Besides identifying plants to family, The Board is an easy way to learn or reinforce the characters of the major plant families. In terms of geographic range, the board is based on Midwestern plant families but should work anywhere east of the Rockies and north of the southern coastal plain. If a family has greater than two genera or seven species I added it to the board. I also added some families that have few genera but several species, such as Clusiaceae, and families that are small but relatively common such as Lythraceae.

Admittedly, the board has shortcomings. Some of the families are oversimplified. Only the more prominent characters for each family are listed. And not every family is listed. But overall, it represents more information than is floating around in the heads of 99% of folks that call themselves botanists, so I feel it is at least justified as a teaching tool. In fact, it will be added to the training material that the Institute of Botanical Training provides for its students.

If you would like your own copy of The Board, you can save or print off the jpeg above. However, this will result in a low resolution copy. If you would like a clean and crisp copy I have saved a pdf version at Scribd.com. Here is the link:

Lastly, The Board is a work in progress. If you have suggestions for additions, subtractions or good old fashioned edits, please let me know. Updating the families to reflect the work of the Angiosperm Phylogeny Group is not an option, so don’t bother suggesting it. For better or worse, the families of their treatment lack cohesive morphological distinctions and would be a mess. Otherwise, enjoy!