Tuesday, January 21, 2014

Spontaneous trefoil?

On the lower left of HS 242 f. 110, one of Lawson's collections, is a label covering what appears to be a plant specimen. It's quite small, and the bit that appears most clearly looks like a trifoliate something-or-other. A Desmodium, perhaps? Who knows. Weakley includes the common name "trefoil" in eight different plant entries - anything with leaves clumped in threes can merit it.

The intriguing thing is the label, which is evocative. (At least, my attempt at deciphering it is evocative.) It appears to read:

"Jan. 27th 1710. Spontaneous [?] trefoil of Carolina growing on the fork of Neus River and in other places having shed [?] from flower like drops of blood a sweet herbage[??] all spontaneous trefoils are more hairy here than in England."

I may have gotten that completely wrong.

But what if I'm right, and it does refer to "spontaneous trefoil"? Did people believe plants could grow spontaneously? Is trefoil a particular weed, common in England?

I found this account in The Farmer's Magazine, London 1851 (MDCCCLI - I hate Roman numerals!) describing a case of trefoil growing in fields sown with clover. Because the seed produced pure clover in most fields, the farmers concluded that the trefoil must have grown spontaneously. The author refuses to believe this, noting that seeds could lie dormant for years until conditions were right for them to germinate, but it is intriguing, no?

Then there's this, from the Annals of Agriculture, and Other Useful Arts, published London 1804: "Gypsum has also another very singular property, that of encouraging the growth of spontaneous trefoil on spots where seed had never been sown, particularly of the yellow and white trefoil. In Alsace I have seen many instances of this singular circumstance."

And this, on the adulteration of forage plants, another author recognizing that yellow trefoil seeds can last a long time.

What is trefoil? I'm not going to attempt to identify this specimen, but I can speculate more on my musings. This UK lawn weed site identifies Trifolium dubium as the noxious weed Lesser Trefoil - it's a Eurasian native, and is introduced to our area, so maybe not that. Plant Guide.org identifies it as Medicago lupulina, also introduced to our area. Weakley includes the common name "trefoil" in eight different plant entries - anything with leaves clumped in threes can merit it.

Sadly, our photographs do not allow us to see through that unfortunate label to further examine the plant specimen. So the mystery will have to stop here for now.

Friday, January 17, 2014

Taxonomic hierarchies

How do we sort things? Let me count the ways....

Modern scientific taxonomy got started with Carl Linnaeus (1707-1778). He was the man, I must say. After spending his younger years exploring the botanical biodiversity of Sweden and northern Europe, he dedicated his mature years to sitting in Uppsala and organizing the pieces of the world that came to him in the mail. Explorers went out to sea at his behest, and some of them - the ones that survived - sent him specimens of plants, animals, stones, whatever.

Linnaeus decided to organize everything. At the time the world must have seemed suddenly knowable, all things coming clear. Everything must belong to a type, and all types must fit into a hierarchical structure. (Could it be Latin grammar that gave him this idea?)

Linnaean organization especially emphasizes two things: kingdom and genus. Kingdom defines the nature of the beast. Genus names a category and allows specification to produce a binomial - a scientific name.

To start with the binomial: The scientific name of a species consists of two names, genus and species. The genus is its generic name, or category. The species is the name of a specific type of organism within that category.

Take the lion, Panthera leo. The generic category is panthers. What kind of panther? The "lion" kind. You could also have the "tiger" kind of panther, Panthera tigris, or the leopard kind of panther, Panthera pardus, which actually means "Panther panther." (The word "leopard" comes from two Greek words meaning "lion panther," so our common name for leopard means the same thing as the scientific name for lion. Haha!)

All those generic panthers belong to the cat family Felidae. So do generic little cats, in the genus Felis, "cat" in Latin. Linnaeus named our domestic cat Felis catus. Catus is another Latin word for cat. So a domestic cat is the "cat" kind of cat. Another little cat is called Felis silvestris, the kind of little cat that lives in the forest. Simple!

Now kingdoms. Linnaeus created three kingdoms - Plants, Animals, and Minerals - to encompass everything in the world. Anything missing? Minerals fell by the wayside pretty quickly, but they weren't the real problem.

The invention of the microscope suggested that microorganisms didn't fit into either Plants or Animals. In the 1860s biologists added a new kingdom, Monera, for all single-celled organisms. But all single-celled organisms aren't alike. Some are small and primitive with no nucleus, and others are large and well-organized with nuclei and membrane-bound organelles. Scientists started calling them prokaryotes and eukaryotes. In 1938 they added another kingdom, Protista, to hold single-celled eukaryotes. The prokaryotes - bacteria and cyanobacteria - stayed in Monera.

Now, fungi are really not at all similar to plants - no chlorophyll, chitin cell walls - so in the 1960s they got taken out of Plantae and put in their own kingdom Fungi. And animals, plants, and fungi are all eukaryotes, so it was kind of important to put them with single-celled eukaryotes if cell structure was going to be a category. But they were ALREADY kingdoms. We needed another level of taxonomy. So that led to the short-lived empires - Prokaryota and Eukaryota. Kingdom Monera went into Prokaryota. Eukaryota got everyone else - Animalia, Plantae, Protista, and Fungi.

But in the 1970s and 1980s, biologists started focusing on common ancestry instead of physical similarity. Microbiologists announced that prokaryotes were not all bacteria, and that some were in fact very very different - so different they deserved their own kingdom. In the 1990s they got rid of Monera and replaced it with Bacteria and Archaea. The empires were changed into domains called Prokarya and Eukarya.

And that didn't even last very long. Now there are three domains. Eukarya still contains animals, plants, fungi, and protists. But the kingdoms Bacteria and Archaea are now in domains called Bacteria and Archaea. This leaves room for more discoveries.

Do we still need kingdoms? Does the genus-species naming structure still work? Clearly many things don't fit into the Linnaean schema. Plant taxonomy is full of subspecies and subfamilies and things just called clades or tribes. Hominin (human ancestor) taxonomy got stuck with a family called Homidae - all the great apes - and several named genera, but then has had to fit lots of categories in between them for extinct taxa. (Chimpanzees are currently grouped in a tribe called ... Panini. That's funny.)

And don't even get me started on the slime molds and water molds! Poor Phytophthora, dumped by Fungi. My kingdom for a kingdom! At least they still fit in Eukarya.

One obvious problem with imposing an organizing structure on the world is that one then forces the world to conform to the structure, rather than the other way around. (It's not an animal, and it's not a mineral, so it MUST be a plant....) On the other hand, we have to be able to talk about stuff. It will be amusing to watch this process unfold over the next decades. Will Linnaeus disappear entirely?

Monday, January 13, 2014

Catesby's bison, Darwin's Scotch Firs, and Roan Mountain

Every fall Patrick McMillan takes his Plant Taxonomy class on a field trip to Roan Mountain, TN, to study island biogeography and the ecology of high grassy balds. He talks about the importance of ecosystem engineers in keeping things stable - in this case, keeping the grassy balds grassy.

Grass won't just stay grassy on its own. Left to its own devices, it often will go back to forest, probably through an ugly transitional stage involving lots of brambly bushes. What keeps the bushes and trees from growing? Large animals. In the case of our grassy balds, it was the bison and Indians that used to roam the Appalachians. (Before that - maybe mammoths? But that's a very long time ago.)

There were bison up in the South Carolina mountains in Catesby's time. He writes about them:

Preface, viii.
"I then went to the upper uninhabited parts of the country, and continued at and about Fort Moore, a small fortress on the banks of the River Savanna, which runs from thence a course of 300 miles down to the sea, and is about the same distance from its source, in the mountains. I was much delighted to see nature differ in these upper parts, and to find here abundance of things not to be seen in the lower parts of the country; this encouraged me to take several journeys with the Indians higher up the rivers, toward the mountains, which afforded not only a succession of new vegetable appearances, but most delightful prospects imaginable, besides the diversion of hunting buffelo's, bears, panthers, and other wild beasts."

In his entry on the Pseudo Acacia, he also mentions the bufello:

Vol. 1, Appendix p. 20, Bison americanus and Pseudo Acacia hispida floridus roseis
"I never saw any of these trees but at one place near the Appalachian mountains, where Bufellos had left their dung; and some of the trees had their branches pulled down, from which I conjecture they had been browsing on the leaves.... I visited them again at the proper time to get some seeds, but the ravaging Indians had burn'd the woods many miles around, and totally destroyed them, to my great disappointment; so that all I was able to procure of this specious tree was some Specimens of is which remain in the Hortus siccus of Sir. H. Sloane, and that of Professor Dillenius at Oxford."

As it happens, there are no Pseudo acacia in the Sloane specimens today, but there are two (00087396X and 00087400J) in the Oxford collections. Patrick has identified them as Robinia hartwigii Koehne, Granite dome locust.

There are no bison roaming the grassy balds today (no Indians burning the locust trees either), though Patrick would love to see them restored. Instead, there are cattle grazing in some areas. The grazed parts are empty and grassy. Just beside those grazed bits are areas with the same basic ecological components but no cattle. Those parts are overgrown with brambles, bushes, trees - no grassy balds there.

Charles Darwin described this phenomenon in On the Origin of Species, in Chapter 4, "Struggle for Existence:"

"How important an element enclosure is, I plainly saw near Farnham, in Surrey. Here there are extensive heaths, with a few clumps of old Scotch firs on the hill-tops; within the last ten years large spaces have been enclosed, and self-sown firs are now springing up in multitudes, so close together that all cannot live. When I ascertained that these young trees had not been planted, I was so surprised at their numbers that I examined hundreds of acres of the unenclosed heath, and literally I could not see a single Scotch fir, except the old planted stumps. But on looking closely between the stems of the heath, I found a multitude of seedlings which had been perpetually browsed down by the cattle. In one square yard I counted thirty-two little trees; and one of them, with twenty-six rings of growth, had during many years, tried to raise its head above the stems of the heath, and had failed. No wonder that, as soon as the land was enclosed, it became thickly clothed with vigorously growing young firs."

"Here we see that cattle absolutely determine the existence of the Scotch fir...."