Cynthia, Hybrids and Genera.
niklasleps at yahoo.co.uk
Sat Nov 9 18:07:13 EST 2002
Right on! What a pleasure it was to read this! The only thing I would add is that taxonomy can be phylogenetic, though where we "cut" the tree into genera, tribes, subfamilies, families, etc will always be entirely subjective (just like all our supposedly objective species concepts).
Bill Yule <droberts03 at SNET.Net> wrote: I can see that this thread is rightfully winding down now and as instigator of both "Cynthia" and "Hybrids and Genera" I'd like to weigh in with some non-professional personal comments. I admit that I've enjoyed the exchanges and opinions tremendously. What started as simple curiosity about the generic name Cynthia and some confusion about why it may be possible for non congeneric organisms to interbreed and what THAT means about the information that the rank "genus" may give us, we have now progressed (notice I don't say drifted) into the philosophy of science and other great subjects. I realize that certain topics re-occur on lists like Leps-l and two of them are here again: What is a "species"? Can taxonomy be phylogenic? I'm just a naturalist with no formal training in either systematics or evolutionary biology but I find these subjects fascinating none-the-less. What follows are some of my "lay" opinions on the subject. I guess the big problem with "species" is that we expect it to be more than it can be. We expect it to be a useful "concept", which is another way of saying an intellectual "tool", and we expect it to have a fixed, unchanging, external, corporeal reality. But we can't have it both ways can we? The bug in my hand is just the bug in my hand. It can't BE "the species" but we can describe as a member of a group called a species(provided we define the characteristics of that group). But "species" as an intellectual tool can help us describe the bug in hand and make predictions about relationships that the bug may have with other bugs (and of course other bugs other people have held in their hands). The species concept is a muti-faceted tool. Did you ever own one of those screwdrivers that has a six-sided receptacle on the end and the different screwdriver "bits" are on a tray that slips over the shaft of the driver and each different bit fits into the receptacle so you can change bits easily depending on what job you need to do. To my mind that's the "species concept". The bit on the tray that we call the "biological species concept" is a useful tool for describing contemporary gene flow in populations. The "morphological species concept" is a tool (a bit on that tray) that every field biologist carries into the field each time they go out, along with a net, collecting envelopes and a shoulder bag. We use that tool, the morphological species concept, that "bit", to make a preliminary determination about each insect that we collect in the field. It is a very useful tool. But it's just a tool, and a conceptual tool at that. Actually it's a temporary mental drawer that we put the bug into until we gather some more data about it. So we can name it! Meanwhile, back at the lab, molecular biologists are taking out their tools; microscopes, centrifuge, phylogenic species concepts, gels, teasers so they can check out a group of animals to see if they are in fact biological species and how closely related they may be to other biological species. I think it's always a fair question to ask, "What good is it?" If species concepts are a multi-use conceptual tool what is the "job" we hope to accomplish. A good question! I don't know the answer. But I do have some thoughts on the matter. (You knew this was coming ;>). One part of the job seems to be that it lays a foundation for naming things. The names may change, evolve, morph, contract, whatever, (and we have invented that other tool the Rules of Nomenclature to guide us) but we humans do seem to need to name things. Another part of the job seems to be to give some form to the smallest units that we use in our attempts to tell the story of evolution: The story of lineages. Of course we have also invented a whole array of other intellectual tools to work on THAT project as well but that's another story.What do we know? Some day I'd like to write the "Idiot's guide to Species". I would write it with myself in mind. It would begin like this: 1. We know that naturally occurring populations of organisms that freely exchange genes have a high degree of morphological, chemical and ecological similarity. We know that these naturally occurring populations defy our attempts to erect neat intellectual corrals (called species) around them so we know EXACTLY what binomial to give them and which drawer we should put them in when we get home. Never the less we DO give them binomials (and sometimes trinomials) and we DO bring them home and put them in drawers. The problem: Some individuals within that intellectual corral jump the fence, run around outside and mate with other individuals who have jumped THEIR fence and escaped from their corral. Some individuals jump the fence and find another corral full of a similar population and jump into that corral, mate and produce offspring. Some individuals sit ON the fence. Nobody knows how they got there or where they came from. Some individuals within the corral are born that don't look or act like the other members of the population. (mutation?). Some corrals are so far removed from each other (or some obstacle separates them) that individuals who jump the fence could never find the other corral to jump in and mate. Gradually the individuals within these two populations start to look and act differently. (speciation event?). Sometimes the obstacle that separated the two corrals disappears, the fences break down and the two populations start to exchange genes. (genetic drift?). Sometimes the corral is so large that individuals at one end never meet up with individuals at the other end. The individuals at these extreme opposite ends look and act differently. (cline?) Sometimes individuals within the corral look and act superficially like all the others but they don't exchange genes. (Cryptic species and/or convergency?). Bottom line. The organisms that we name "species this" or "species that" run wild, obey no rules (except the rule of survival), and have no names. Our species concepts are little more than branding irons that we attempt to apply to a passing herd stampeding by at an evolutionary gallop. All these exceptions to the purported "usefulness" of the tool of a species concept make it suspect as a useful tool. Yet it still seems to be the best tool for the job. What is the job? Naming organisms and begin to describe their relationships. If we can't agree on a definition for species all the ranks above in the Linnean hierarchy become suspect for their respective usefulness. That's why I asked the question about "genera"? If non congenerics can interbreed and IF (a big if!) they produce fertile offspring what does genera mean? What information does that term now contain? I don't know. It's a hypothetical question. But I think there is an agreement about the usefulness of species concepts EVEN IF THERE ISN"T AGREEMENT ABOUT DEFINITIONS. I think we still carry that screwdriver around, changing bits as necessary, getting on with the job. Or jobs. The jobs of naming organisms and describing relationships. Which brings up the other subject. Can taxonomy be phylogenic? It probably should be and can try to be so. But it must be other things simultaneously: An organizing principle, a way of categorizing (putting things in drawers). If it's true that "Nomenclature is the Handmaiden of Taxonomy" as Marinus Anton Donk said, and if Taxonomists have reinvented themselves nowadays as "Systematicists" (and systematicists are mostly cladists) then maybe we are moving in the right direction. Maybe nomenclature can be the handmaiden of cladistics and we can maintain the Linnean hierchey in a way that organizes for easier comprehension and tells the story of evolution at the same time? I'm rapidly approaching the point where I don't have any idea what the hell I'm talking about so I'm ending here. If you lasted this far thanks for hearing me out. I'm sure that some of my thoughts are less than 100% accurate and admittedly fuzzy thinking does occur in my brain. Feel free to comment or correct...;.} Bill Yule
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