Some might suspect we are species hounds at Paint Rock Forest Research Center, obsessed with finding new species.
Ed Wilson reminded us often that we should be. He wanted us to know every species on the preserve, including the 80 percent of species that none of us know.
And we seem to be doing that, a small piece at a time. We’re in the drawn-out process of unravelling multiple species mysteries that could result in newly named species of oak, maple, buckeye, dogwood, azalea, hickory, violet…the list grows year by year. We hope that list will soon include insects, vertebrates, fungi, cave life, aquatic life that no one has ever heard of before.
Some might even accuse us of being deliberate “splitters” – a label that some botanists lob at those they feel are just trying to devise new species based on “minor” character differences that don’t matter. If splitting involves having to learn a bunch of new Latin names, there’s usually a snarl attached to the name-calling.
But what’s more important to us than finding new species is beginning to understand what a species really is, conceptually and individually.
Oh, you thought we already figured that out? Well, no.
In fact, scientists around the world are rethinking conventional species boundaries. A giraffe, we now know, isn’t just a giraffe. It’s a complex of four very distinct species, with nine different subspecies that are all on separate evolutionary paths. Why did it take so long to understand that?
It’s partly because we’ve long had a very crude and cursory way of looking only at the mostly obvious physical characteristics where species are concerned. But giraffes are more than just long necks, and now we see quite clearly that there are species of giraffe that are not only genetically distinct, but also (on closer inspection) different physically, with different adaptations to the massive differences in habitat and communities across Africa. In the face of changing climate and human impacts, the future of giraffeness may depend on recognizing and preserving all those species and subspecies.
The same reckoning is happening here in the Southeast. For years, we were content with hand-me-down descriptions of species, often from elsewhere in the country where species diversity was less rich, and perhaps a bit easier to describe and master.
I continue to be amazed at how simplistic our notions of southern species once were. Who can look at the leaves and fruits of Southern shagbark hickory, and not immediately see how different it is from Northern shagbark? Who could ever have possibly thought pagoda oak and Southern red oak were the same species? How could anybody mistake Cumberland hill cane, with its distinctive short habit and deciduous leaves, for the “giant” evergreen cane of our river bottoms? And yet, until the past few decades, these plants were all lumped together and their conspicuous differences largely ignored.
Species definitions have always been shaped by our ability to see the differences in things, and by our willingness (or not) to see the difference. Foresters in the early part of the 20th century didn’t have the tools to easily see the genetic differences in trees, but when a dozen species of red oak were going to be mixed at the mill and bring the same price, they didn’t see much need to discern them either.
A new generation of taxonomists, like Alan Weakley and Bruce Sorrie in North Carolina, Dwayne Estes, Robert Kral and Jayne Lampley in Tennessee, Brian Keener and John Freeman in Alabama, and Jim Allison in Georgia, have challenged us to look again at familiar groups like hickories, oaks, violets, wild gingers, trilliums and many others.
What we now see are not just subtle distinctions, but distinctions that can make a world of difference. The difference may not be easily and immediately discernible by leaf shape, or bark, or even flower or fruit. But it can sometimes be easily parsed in the distinctive genetic makeup of each new species.
That was the great surprise with the American elms of the Cumberlands. They, along with elms from a few other spots in the Deep South, were so genetically different from American elms up north they couldn’t effectively interbreed and share genes. They were reproductively isolated, and apparently had been for millions of years. There’s no more firm dividing line between species than that. The truth is, we still don’t have a key that makes it easy for us to tell them apart in the field. But why should that have ever mattered to the elms, as they were shaping their separate evolutionary paths?
More importantly, why should any of this matter to us? If there’s no significance to finding these new species, then we’re all just collectors, with our little species trophies sitting on our shelves like bric-a-brac.
But the recent discovery of a potentially new “hidden” American elm species demonstrates why it’s so important to re-examine what a species is, conceptually and individually. Those hidden species may have extraordinary resistance to the diseases that have wiped out elms across the rest of the country. In large measure, the radically distinct Southern/Cumberland version of American elm was “discovered” not because it looked conspicuously different, but because a few of its progeny were so conspicuously resistant to disease. Recently described species within the white ash group may have characteristics that help us better respond to the threat of emerald ash borer. Still largely unexplored differences in the butternut group may help us understand why one of North America’s most delicious nut trees is still thriving in Paint Rock, even as it’s near extinction most everywhere else.
Call us “splitters” if you like, but when splitting makes a difference to the future existence of the elm genus, we’ll take that as a compliment.
Each time we refine our ideas about what an individual species is, we also can sharpen our idea about what a species should represent. And it may be we need a much more refined language of species that truly captures the broad and often very important differences between populations and individuals, even when they don’t fit the classic definition of separate species.
Once again, Paint Rock and the Deep South should be the testing ground for these new concepts. We’ll talk about that next time.