OOOPS! Goofed up, so continued here...
It is immaterial whether or not the term isolating mechanism was well chosen, nor is it important whether one places the stress on the prevention of interbreeding with non-conspecific individuals or the facilitation ("recognition") of breeding with conspecific individuals. The concept I have just developed is articulated in the so-called biological species definition: "Species are groups of interbreeding natural populations that are reproductively isolated from other such groups." The isolating mechanism by which reproductive isolation is effected are properties of individuals. Geographic isolation therefore does not qualify as an isolating mechanism.
So, what do you do with canines, seagulls, equines and bovines that are separated by geography and genetics, only to cross, successfully, once placed in proximity by human intervention or migration?
Botanists soon pointed out that this did not correctly describe many situations in nature. They discovered case alter case of occasional (sometimes even rather frequent) hybridization between seemingly "good" sympatric species.
Yes, I began in my examples with plants, but as my previous comment shows, it reaches into higher mammals as well.
After the destruction of much of the southern periphery of the habitat of the gray wolf, the area was invaded by coyotes and, owing to the fertility of the hybrids, the crossing of male wolves with female coyotes led to an introgression of alien genes into both wolf and coyote populations. The same was shown by Templeton and associates (1989, 12) for the sympatric Hawaiian species Drosophila silvestris and D. heteroneura. The fact that the mitochondria are inherited only through the females greatly facilitates the discovery of such cases of hybridization.
Which directly acknowledges at least one of my examples.
It is thus well established that a leakage of genes occurs among many good "reproductively isolated" species. This induced me to revise the definition of isolating mechanisms to "biological properties of individuals which prevent the interbreeding [fusion] of populations"(1970, 56). Thus, isolating mechanisms do not always prevent the occasional interbreeding of non-conspecific individuals, but they nevertheless prevent the complete fusion of such species populations. Clandestine hybridization is apparently far more common among plants than among higher animals.
Whether more frequent in plants or animals is irrelevent. Complete fusion is irrelevent. What is, in nature, is. I just have not yet seen it
accurately described.
Among the invalid objections to the biological species concept is the claim that it would work only if the acquisition of the isolating mechanisms was a teleological process (Paterson 1985).
I have deliberately avoided this in my discussion, but the teleological "connection" is irrelevent. This is this author's attempt to dismiss God "out of hand." That is not his place, nor his field of magisteria (in Gould's terminology).
The evolutionist always stresses the genetic uniqueness of every individual of a sexually reproducing population. However, the members of any species also have in common many species-specific properties. This includes, in particular, the isolating mechanisms but also many adaptations, for instance, for niche utilization, as well as certain contingent, species specific properties. If one knew the genetic basis of all the species specific characters, one might be able to give a genetic characterization of a species taxon.
Ah! Now we are getting to the meat of the matter!
IF one knew, but all too often in the papers I have read it is evident the full scope of the complexity is ignored or grossly simplified. Again, I am beginning to think there is a "political" motivation behind this, and ultimately it is used to support the memetic dogma of Darwinian philosophy, even in the face of distinct contrary evidence, as stated above!
The BSC is based on the recognition of properties of populations. It depends on the fact of non-interbreeding with other populations.
I can agree with this, if it in fact is the basis for the term and is used as such. When there is conflict, the designation must be broadened. Or the term must be redefined. "They" can't have it both ways! So when a particular creature begins to exhibit an adaptation, it does not delineate a species. I think if you reconsider the list you posted earlier, you will find several examples I have already gone over, that posit this very quandary.
The two meanings of the term species. What the scientist actually encounters in nature are populations of organisms. There is a considerable range in the size of populations, ranging from the local deme to the species taxon. the local deme is the community of potentially interbreeding individuals at a locality (see also Mayr 1963. 136), and the species taxon has been referred to by Dobzhansky as the "largest Mendelian population." The task of the biologist is to assign these populations to species. This requires two operations: (1) to develop a concept of what a species is resulting in the definition of the species category in the Linnaean hierarchy, and (2) to apply this concept when combining populations into species taxa.
A number of recent writers on the species problem have failed to appreciate that the word 'species' is applied to these two quite different entities in nature, species taxa and the concept of the category species. As a result, their so-called species definition is nothing but a recipe for the demarcation of species taxa. This is, for instance, true for most of the recent so-called phylogenetic species definitions. It is also largely true for Templeton's (1989, 1994) cohesion species concept. A paper often quoted as a decisive refutation of the BSC (Sokal and Crovello 1970) is perhaps an extreme example of the confusion resulting from the failure to discriminate between the species as category (concept) and as taxon.
My point. If those "in the know" can't get their own understanding and relating of the term correct, how can any of them expect the rest of us to follow? Rather it seems to me, (deliberate or not) to be a confusion that is fed, and fed well, perhaps in an effort to dogmatize the meme among the masses. If it can be made sufficiently vague, then masses will accept without question becasue it is too much bother to ask and/or explain. If "you" don't believe, well then you are just an illiterate heretic!
(1) The species taxon. The word taxon refers to a concrete zoological or botanical object consisting of a classifiable population (or group of populations) of organisms. The house sparrow (Passer domesticus) and the potato (Solanum tubersum) are species taxa. Species taxa are particulars, "individuals," biopopulations. Being particulars, they can be described and delimited against other species taxa.
No problem, and I've stated as much.
(2) The species category. Here the word 'species' indicates the rank in the Linnaean hierarchy. The species category is the class that contains all taxa of species rank. It articulates the concept of the biological species and is defined by the species definition. The principal use of the species definition is to facilitate a decision on the ranking of species level populations, that is, to answer the question about an isolated population: "Is it a full species or a subspecies?" The answer to this question has to be based on inference (the criteria on the basis of which such a decision is made are listed in the technical taxonomical literature, e.g., in Mayr and Ashlock 1991, 100-105).
This is where things get dicey. When a finch adapts its beak, it is considered a species (see the earlier post by another). Yet, if it is still able to reproduce among finches, any or all, it is not a distinct species
by the previous definition. This is where the confusion lies, and the "religion" of science is not generally forthcoming about these things. I have my own suspicions as to why, and they deal with power, money and politics. It is still a religious "war" waged between science and religion proper. (Although in fairness, war may be too harsh a word. Nevertheless, it is a battle of memes (thought processes, one could even say "philosophy." Oh yeah, someone already did...)
I will stop here for copyright considerations, however, there is a clause in those laws that allows for educational and intellectual discussion of copyrighted material, provided the author is acknowledged. So I will here state that the above quotes that are not from Vajradhara are from the second link he posted. To wit: "What is a Species, and What is Not?, by Ernst Mayr, Originally Published in Philosophy of Science, Vol. 63 (June 1996) pp. 262-277."
http://members.aol.com/darwinpage/mayrspecies.htm
