Posted on 08/24/2006 6:54:24 AM PDT by PatrickHenry
Criterion or circumstances |
Biological Species Concept |
Morphological Species Concept |
Phylogenetic Species Concept |
Genetic Species Concept |
1. Diagnosably distinct populations recognized as a separate species |
Sometimes |
Most times |
Always |
Yes, if genetic distances are typical of sister species |
2. Species unit often includes diagnosable allopatric populations |
Yes, subspecies concept widely accepted |
Yes, subspecies concept widely accepted |
Never, subspecies concept not relevant |
Yes, subspecies relevant but defined genetically |
3. Species represent terminal taxa that can be used in phylogenetic and biogeographicalanalysis |
Sometimes |
Sometimes |
Always |
Always |
4. Inherently provides accurate historical information |
No |
No |
Yes |
Yes |
5. Gene flow among species |
Rarely, if ever |
Not directly |
Sometimes |
Acceptable |
6. Reproductively isolated populations recognized as separate species |
Always |
Always |
Always |
Always |
7. Extensively hybridizing, diagnosably distinct populations important for establishing species status |
Rarely |
Rarely |
Almost always |
Yes, if integrities of the 2 gene pools are protected |
8. ‘‘Potential’’ interbreeding of allopatric populations important for establishing species status |
Yes |
Yes, estimated by morphological divergence |
Never |
Yes, estimated from genetic distance of nuclear and mitochondrial DNA |
9. Delimitation of areas of endemism |
Coarse, less precise |
Coarse, less precise |
Fine, more precise |
Fine, more precise |
10. Inter-and intraspecific genetic biodiversity documented |
Sometimes |
Rarely |
Sometimes |
Always, with adequate sampling |
11. Estimate of time of origin |
No |
Sometimes, if fossils available |
Sometimes |
Always |
12. Provides foundation for Barcode Initiative |
No |
Yes, through voucher specimens/binomial names |
Sometimes |
Always |
13. Resolves geographic limits for cryptic species |
No |
No |
Sometimes, if gene trees are used |
Always, with adequate sampling |
14. Can be influenced by local environmental conditions |
Yes, if morphology database used |
Yes |
Yes, if morphologic database used |
No |
Some type of statistical variation based on genetic information would be best. Some form of cluster analysis would be a great way to go, but it would likely entail multidimensional space to do it well and that is not something easily visualized or intuitively comprehensible to someone not familiar with things like Mahalanobis distance measurements. But it would be more quantitative and would allow biologists to determine the classification in which an individual would most probably be a member of and groups that an individual would most probably not be a member of.
Such statistical analysis is used routinely in spectral analysis where samples are mathematically segregated based on spectral response. A spectrum, regardless of type, is a linear array. A genome could also be represented by a linear array so the statisitics would be directly analogous.
You would not believe what DNA studies are doing to fungal taxonomy. Looks are turning out to be near irrelevant... even families are being messed up.
"I am very puzzles why we must find a sharp deliniation between types of organisms."
Simple - humans love to pigeonhole things and if something doesn't exactly fit, they make it fit.
Humans don't like "messy" things, so we force a sometimes artificial format onto things that don't necessarily work by the same rules.
The microbial world is full of things that "don't fit" - most of us gave up long ago trying to make them fit and have retreated to "this belongs somewhere between X and Y, and until we know more it's not worth the time and effort to try to clearly define where it is".
Fungal taxonomy has always been a mess. The very large group of Fungi Imperfecti was nothing but a catch-all for anything that couldn't be more clearly defined. While, periodically, some member of the Fungi Imperfecti would get moved out into the Ascomycetes or Basidiomycetes, more were being added at the same time.
20 years from now we might have a good picture of the whole fungal mess.
If it weren't for extinctions, the inter-relatedness of all species would be as immediately obvious as it is among all varieties of dogs.
What you say here is very close to what I was thinking. What I propose is a quantitative measure of how far between X and Y is the thing? But not only how close to X and Y, but to all organisms. Most organisms would be so distant, they would be like the background of stars compared to observed planets from Earth. But there would not only be a 'distance' relationship, but also a 'directional' relationship.
Changing definitions seems to be the order of the day. Planets were redefined, twice in one week because of the newly discovered Kuiper belt objects, one larger than Pluto. They will probably redefine race as well.
Darwin was aware of the fuzziness of the definition, and found that it made no sense in trying to decide anything regarding humans:
We might as well attempt without any definition to decide whether a certain number of houses should be called a village, town, or city. We have a practical illustration of the difficulty in the never-ending doubts whether many closely-allied mammals, birds, insects, and plants, which represent each other respectively in North America and Europe, should be ranked as species or geographical races; and the like holds true of the productions of many islands situated at some little distance from the nearest continent.Source: Darwin, The descent of man: CHAPTER VII. ON THE RACES OF MAN.
Philosophers have the approach of trying to understand other philosophers as best as possible first, then moving to other interpretations. Even so, one philospher might call Plato an Idealist and Aristotle a Realist while another might point to Aristotle as the Idealist. What one means by saying Species is probably never going to be exactly what someone else means even if they have an international conference and vote.
It is not really a scientific issue. It is semantic. Currently, the word "species" is generally used to refer to critters who can mate together and produce viable offspring. That is a useful concept that should have a label.
The attempted redefinition refers to a different concept related to genetic diversity. Thus, they would change the meaning of a label instead of just coming up with a new label for the new concept. (One could just as well use something like "genetic diversity segmentation" to refer to that same concept.)
But giving this new concept a new name would not have the desired political results. Therefore, this is politics masquerading as science.
Thanks for the ping!
Does race have a definition?
It has at least one depending who is talking. The Bureau of the Census has quite a list, but anthropologists tend to identify three depending mostly on hair type.
So there is no objective definition of race, just lines drawn by people with agendas.
Pot ... kettle ... black....
If it weren't for extinctions, the world would be so crowded we'd all be dead.
Well, politics and other biases seem to be big on some terms that cause heat just by saying.
Well, damn, I wonder why the word race is politically charged.
Yesterday someone tried to paint Darwin as a racist because the word appears in the subtitle of "Origins."
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