This can be a controversial subject, as when a development project is stalled or ended because it threatens a rare or endangered species. Therefore, let's define our terms.
A naturally occurring living thing can be "rare" in two main ways. First, it can be rare in the sense that it is nowhere common. Usually that's because its habitat requirements are very specific, and this habitat itself is rare.
For instance, a very rare bird sometimes occurring in the southern part of our Loess Hills is the Red-cockaded Woodpecker. This bird is almost completely dependent for nesting on old Loblolly, Longleaf, Slash, and Shortleaf Pines, especially those afflicted with the fungal disease called red heart, or red-ring rot, which attacks the trees' heartwood. The bird prefers open, park-like woods such as those maintained by occasional burning.
Even before humans came along with their intensively managed forests where trees are cut before reaching old age, and forest fires are controlled, Red-cockaded Woodpeckers must have been a bit rare.
The second main way an organism can be rare is for small populations of it to survive in pockets beyond or outside the geographcial area where it is normally found, and may be considered "common." there. The Allegheny Pachysandra is such a plant in our Loess Hills. This species is most common in the Appalachian Mountains, but does occur sporadically and rarely here and there elsewhere in the Southeast. Allegheny Pachysandras in our loess zone are occupying the extreme western frontier of their distribution area. They are rare "here" but not so rare in the Appalachians.
The implication is that those individual organisms who do somehow manage to survive in the border regions of a species' general distribution might possess some special talent or adaptation enabling them to survive, thus their genetic inheritance assumes special importance. The map at the right shows the distribution of the vine called Bittersweet, Celastrus scandens. The map shows that Bittersweet is common in central Kentucky and Tennessee, but then disappears in the western parts of these states, before reappearing in our Loess Hills. Is the isolated population of Loess-Hill Bittersweet in some important genetic way different from that of the main population found throughout the northeastern US? By the way, that locality in Arkansas is also on loess. The map is adapted from Wilbur H. Duncan's Woody Vines of the Southeastern States, appearing in Volume 3, Number 1 issue of SIDA, pages 1 through 73.
The next term to deal with is "endangered." In the United States, the most important definition of this term is the one decided on and published by the U.S. Department of the Interior. There's no need to debate about the nuances of the Department's definition, for what's important is the list of species the Department says is endangered. If the list says the species is endangered, then, in the U.S., legally, it is endangered. You might like to visit the US Fish & Wildlife Service's Web page on Endangered Species.
A salient feature of this list is that it can be changed. If enough members of Congress decide that the list should be pared down, or that new species should be added, it will be done.
Finally, the term "species" is important. We know that Red-headed Woodpeckers and Red-cockaded Woodpeckers are "different species of woodpecker," so, in this sense, a species is a "kind" of organism. Traditionally a more technical definition has been that a species is an interbreeding, or potentially interbreeding, group of organisms that in nature does not interbreed significantly with any other group.
Therefore, since Poodles and St. Bernards, despite their very different appearances, are able to interbreed to produce mongrel dogs, Poodles and St.Bernards are both members of the dog species. They are different races, in the same way that oriental people and white people are different races.
The definition for species says "...does not interbreed significantly with any other group." The word "significantly" must be emphasized because sometimes two seemingly very different species are discovered to be perfectly capable of interbreeding. However, they don't interbreed enough for the two apparent species to melt into one another.
For example, the Blue Jay is a common bird throughout the loess bluff zone. In western North America there's another jay called the Steller's Jay, and it looks so different from a Blue Jay that it would hardly occur to anyone to question whether the two bird types might in reality be the same species. Nonetheless, it's been found that in a tiny part of Colorado where the distributions of the two species overlap, they do indeed mate, producing intermediate-looking offspring.
Therefore, are the Blue and Steller's Jays one or two species? It could be an important question if one day the Steller's Jay, we'll say, is facing extinction and someone wants to save it. A developer says, "But technically it's the same species as the Blue Jay, and out East Blue Jays are common as sin!"
As it turns out, the U.S. Department of the Interior is interested not only in protecting species, but also subspecies. Thus the Spotted Owl, Strix occidentalis, occurs from southern Mexico to southwestern British Columbia, and is not considered to be endangered. However, at its northern extreme a subspecies or race has evolved, the Northern Spotted Owl, Strix occidentalis ssp. caurina, which is indeed endangered by forestry practices. Consequently, some forests in the U.S. Pacific Northwest have been set aside for this subspecies's protection, to the profound consternation of many people dependent on the timber industry -- even though the Spotted-Owl species itself is not endangered.
Subspecies, then -- at least at this writing -- is an important concept. When referring to plants, usually instead of referring to subspecies, "varieties" are spoken of. The word "race" is nowadays considered too vague to be very useful, and for our purposes we can do without it.RARE AND ENDANGERED SPECIES IN THE LOESS ZONE
No even half-way thorough search has been conducted searching for rare and endangered species throughout our Loess Hills. One reason for that is that so far only a few specialists have considered the loess zone a unit with sufficient identity to study it. Another reason is that our part of the country is probably the least studied major life zone of all in eastern North America.
However, a few limited studies have been done, and these point to some interesting inhabitants in our loess zone.
In the early 1990s the U.S. Forest Service funded a search for rare plants in southwest Mississippi's Homochitto National Forest. Though only about one percent of the forest was surveyed, and most of the study sites were far from deep loess, three study sites were designated in locations mantled in thin loess, which was mostly intermingled with regular soil.
In the three "thin loess" study areas, known as Pipes Lake, Pellucid Bayou, and Big Hollow, the investigators found the following plants, which they considered to be "special," but not "threatened" or endangered:
Allegheny Pachysandra: A member of the boxwood family, a little like a large-leafed ground-ivy with spikes of tiny white flowers, found in rich, deciduous woods; flowers March, April; distributed from the southern Appalachians into Mississippi, Alabama, and western Georgia, with notable islands of "disjunct" populations in Louisiana's Tunica Hills, Laurel Hill Plantation in southern Mississippi, and in Jackson County, Florida.
Climbing Hempweed: A member of the composite family, a vine with large clumps of tiny white flowers, found in moist places, especially calcareous soils; flowers September to December; a tropical and subtropical plant, with us at the northern extreme of its distribution. Very similar to a more common vine also called the Climbing Hempweed, from which it can be distinguished by technical characters.
Fetid Trillium: A member of the lily family, a wonderfully fragile spring wildflower with dark purple to yellow blossoms smelling of rotten meat, found in rich woods and ravine slopes; flowers April to May; distributed in Louisiana east of the Mississippi, and southwestern Mississippi, thus constituting a species with a very limited distribution.
Scarlet Woodbine: A member of the magnolia family, a woody vine with small crimson flowers, found in rich woods and ravine slopes; flowers July, August; distributed along the Coastal Plain from North Carolina, Florida, to Louisiana and eastern Arkansas, with us fairly frequent on the loess bluffs but sporadic elsewhere.
Silky Camellia: A member of the tea family, a shrub or small tree with white camellia blossoms, found in rich woods and ravine slopes; flowers September, October; distributed along the Coastal Plain from Virginia to Florida and Texas and Arkansas, in Mississippi sporadic in the southern one-third of state.
Single-headed Pussytoes: A member of the composite family, vaguely resembling a fuzzy, thick-stemmed Dandelion with a white cluster of tiny flowers, found in open woods and dry ground; flowers March, April; distributed from Virginia to southern Indiana south to Georgia and Louisiana, so we are at the southwestern extreme of its distribution.
Southern Wood-Fern: An evergreen fern with astonishing genetics. It is a "sterile triploid hybrid" between the Log Fern and the Louisiana Wood-Fern. In other words, the two fern species have interbred to produce a hybrid fern, but the hybrid, our Southern Wood-Fern, produces only abortive and misshapen spores, and is thus unable to reproduce, except vegetatively, by underground rhizomes; found around shaded seeps. Extremely spotty occurrences in the southeastern U.S.