Wednesday, December 31, 2008

Fight or Flight on the Shortgrass Prairie

In early September, I took a little trip to eastern Wyoming. It wasn't the best time of year to visit the Great Plains since late summer is predominantly crispy and brown on the Shortgrass Prairie. However, I was able to find some color here and there.

The area receives an average of 12 inches of precipitation annually. These arid conditions have resulted in a significant percentage of annuals in the flora. Cryptantha crassisepala (photo below) is a fine example. The hairs of the inflorescence are very stiff and are quite pleasing to the touch. With its numerous scorpioid cymes the plant is visually pleasing as well. In the very center of the photo is the final flower of what would have earlier been a much prettier display.

Here on the Great Plains, as with much of Earth's surface, anthropogenic disturbance has significantly altered the ecological integrity of the presettlement natural communities and dramatically changed the natural distribution of plants and animals. Exotic species that are more tolerant of excessive disturbances in biotic and abiotic structure now thrive. Native plants that evolved into the biotic components of the Shortgrass Prairie system were once numerous and well distributed. However, cheap beef to feed a growing nation justified unrestrained grazing. Within a few decades little more than Sagebrush, Tumbleweeds, dust and cowpies were left on the lonesome prairie.

Sadly, the Tumbleweed (Salsola iberica; a.k.a. S. tragus; a.k.a. Prickly Russian Thistle) has become an emblem of the west, but it no more belongs on the prairie than cattle or sheep; cowboys or spurs. It is a nasty, practically leafless plant covered with thorny bracts. Its diffuse branching gives the plant a globose silhouette. When its seeds have ripened, it breaks off at the base and harnesses the wind to roll and bounce its way across the landscape distributing its seed far and wide; or at least until it hits a fence. Here is a photo of it in flower. Note the spines behind each flower. They are very sharp and most unforgiving. Classically a western weed, it is actually found throughout North America, though less common in the east and south.

Amid the waycross weeds and cow patties, I was able to find some interesting native plants. In over-grazed country such as this, one could classify the native plants into three categories; those that hide from grazers, those that fight grazers and those that suffer local (if not global) extinction.

The hiders are either growing in association with some form of grazer deterrent such as a clump of spiny Tumbleweed. Or they seeking refuge in the most floristically rich remnants of the whole prairie region; road ditches. It is here that you find the shattered remains of a once functioning ecosystem shamefully cast with road kill, Wal-Mart bags and cool season Eurasian grasses.

Here is Lygodesmia juncea (Skeletonweed) hiding in a prickly pear.

Other plants found hidden in the thorns include two species of Machaeranthera. The blue flowered Machaeranthera canescens was probably the most common native bloomer I found during my visit. Just about anywhere sheep couldn't get their chompers, this plant was growing.

Machaeranthera canescens was pretty easy to key out and was in most of the wildflower guides I had with me. However, M. pinnatifida (below) with its yellow florets posed a real challenge. I don't know many eastern genera that have yellow AND blue flowered species, so though the keys would take me to Machaeranthera, I wouldn't accept it. Finally, I ran it through the key to species and found the error of my ways. It still doesn't sit right, but I'm sure far greater minds than mine have agreed to it.

Machaeranthera pinnatifida was one of the few plant specimens collected by Meriwether Lewis on the Voyage of Discovery. As with most of the Lewis collection from said journey, it was described by Fredrick Pursh. So the story goes, he was only supposed to look at the specimens while visiting the States. Instead, he smuggled a stack of them back to England where he described them. In a twist of irony, most of the unabducted specimens were severely damaged or lost. Thus through Pursh piracy do we have any undamaged plant collections from the famous excursion.

Here are some road ditch refugees I encountered. This is Senecio riddellii. This was the only specimen I saw and it was closer to the mountains in a transitional area.

Unfortunately, even road ditches are rarely safe for plants that have escaped grazing. Humans have no tolerance for "unmowed" areas. So, in the name of duty to an ill perceived aesthetic, road ditches across America are regularly mowed. Here is a photo of Heterotheca canescens that I would say is standing defiant, if its defiance did not come in the form of lying procumbent. Normally an upright plant, it has become prostrate in the face of the mowing.

My third category consists of plants with weapons. These fighters defy cattle and sheep with raised swords (thorns/spines/prickles) or toxic potions (alkaloids and other sap-based chemical concoctions of a toxic nature). Gutierrezia sarothrae is of the latter persuasion. It is one of several poisonous native species that increase with grazing. Toxins within the plant tissues cause abortions in cattle and sheep (no Roe v. Wade here).

Other species like Grindelia squarrosa avoid grazers simply by tasting bad. This strategy becomes less and less effective the more a pasture is grazed and as the hierarchy of "tasty" shifts downward. The capitula of Grindelia squarrosa are covered with a sticky resin. From this resin the common name "Gumweed" is derived.
Chrysothamnus nauseosus (below) is another species that cattle and sheep find unpalatable. That being said, it must taste pretty bad because this species and Ambrosia tridentata (Big Sagebrush) are often the dominant species throughout the region.
The photo above was taken in a sand blow which was one of the few places that harbored a significant number of native species. I deduced from the lack of sheep and cattle tracks in the area that sheep and cattle do not like to walk in sand. Nor do I, for that matter. However, all around the sand blows there were more hoof printed spots than not. Don't tell the ranchers or they'll introduce camels.
In summation, my short trip to the Great Plains of eastern Wyoming reinforced several facts for me. That most every landscape across the nation is severely degraded, abused and disrespected. That no matter where he goes, the lover of raw and pulsing nature has to search much to hard to find his once ubiquitous treasure. That when truly beautiful things are relegated to the trash strewn ditches and thorny patches of life, the literal becomes a metaphor of our human hour and inevitable decline. And that one day the prairie will reclaim its kingdom.

Wednesday, December 10, 2008

The Love Affair of Gaura biennis and Schinia gaurae

I don't know if it was the cool temperatures, the abundant rainfall or some other stochastic influence, but Gaura biennis was extremely flamboyant in the Ozarks this summer. Everywhere I went, large, diffuse inflorescences of white turning to shades of pink were found.

Admittedly, I have mostly ignored Gaura biennis over the years; finding it gangly and somewhat weedy. But it really out-did itself this year and I took notice. Camera in hand, tripod in tow, I headed down my gravel driveway to a nice specimen for a quick photo. Knowing them to be nocturnal bloomers and having noticed that the flowers were at their peak in the morning when I left the house and mostly shriveled by my evening return, I got to them just after sunrise.

After taking some quick photos, the kind where you don't really see the subject for the equipment, while rushing to beat the light, wind or self-imposed time constraints, I began to study the flowers. In this conscious effort to slow-down and enjoy the moment, the flowers struck me as peculiar. The perianth was tilted about 45 degrees toward the sky, and the stamens where all lined up perpendicular to the ground with the style between the stamens but dropped below their line by a few millimeters. It was the arrangement of the stamens that most drew my attention. I couldn't help but notice that they formed a triangle in outline. Further study revealed a ring of nectaries encircling the base of the style and that the anthers split along the uppermost edge. This made me think about pollinators.

Returning to the house, I grabbed my copy of "Butterflies and Moths of Missouri" and looked for moths that feed on Gaura that might fit what has to be an interesting pollination syndrome. I found that Schinia gaurae (the Clouded Crimson)(picture below from feeds, nectars, rests and lays eggs on species of Gaura and primarily on Gaura biennis. Still curious, I googled for images of this fun little moth. Several of the images demonstrated that the moth is almost the identical size and shape of the stamen arrangement on the Gaura biennis flowers. I also noticed that the back end of its wings are somewhat fluffy, not unlike miniature feather dusters. To cap it off, the adult moth's peak emergence is well in line with the bloom dates of G. biennis.

So at this point I am thinking that Schinia gaurae obviously visits the flowers to get a little nectar and as it aligns itself to drink, the fluffy wing bases get dusted with pollen. It just makes too much sense. Unfortunately, the only references I can find says that G. biennis is pollinated by long-tongued bees. My dream of a "form meets function" world instantly goes up in a cloud of disappointment. After all, what do these Gene Simmons bees have to do with my elaborate Gaura stamens? Are there really nocturnal bees? I needed more info.

I decide to wait until the dead of night before I visit my little population of flowers. At 1am I just can't stand it any longer. I jump in the truck which has become nothing more than a mobile flashlight at this point, and head down the driveway. I get out and eye every flower....nothing. I look closer and find the nectaries, which were dry during the day, are now pumping huge luscious drops of nectar. I must taste one, and I do. It's sweet, but hardly a meal for a curious primate. I also notice that the style is now in line with the anthers and not below them as in the flowers from the day, or should I say night, before. In the anticlimax, I stand a moment, hoping to hear an owl or something to salvage the night, when I notice an erratic flash in the headlights. It's a moth. Surely it is just drawn to the light. It lands on a flower. It's Schinia gaurae!!!! It lights, aligns itself, and drinks. The stamens are covered, the wings are in contact with the anthers and I am ecstatic. I watch for a while, then jump in the truck and head home for a beer and some contemplation about how wonderfully cool life and life on earth is.

Of course, the scientist in me realizes that this merely constitutes circumstantial evidence and in no way proves that Gaura biennis is pollinated by Schinia gaurae. And since I still don't know what the interaction of the plant with long-tongued bees is, they cannot be ruled out. But the novice naturalist, the child, the innocent believer in me is satisfied. At least until next year.