Posted by:
Wulf
at Mon Oct 25 12:44:05 2004 [ Report Abuse ] [ Email Message ] [ Show All Posts by Wulf ]
Hi Wolfgang,
>>Consensus would acutally still accept propsals based on e.g. the BSC, wouldn't they?
You wrote:
Consensus is what develops over time after a proposal is first made in the literature - an increasing proportion of workers will either use or disregard the new arrangement. Also, where you look will make a difference. If a new taxonomic proposal is well supported, then academic publications will usually accept it quickly, whereas it takes a bit longer to percolate into the herpetocultural literature and when it comes to the taxonomic literature - consensus becomes synonymous with intertia. The average toxinological journal comes straight out of the 1960s when it comes to the taxonomy used.
Ok, so far so good, but what makes them disregard a given proposal? I understand that weak arguments or results provided in a proposal make other workers do so, but proposals with adequate data are also often discareded, because of more or less "ideological dissensions".
On the other hand evidence-free papers are widely accepted. I remember Stull (1935) placing the white-lipped python (L. albertisii Peters & Doria 1878) as subspecies of Liasis fuscus Peters 1873 without providing neither reasoning nor any evidence. This proposal was widely accepted (Loveridge 1948, de Haas 1950, Brongersma 1951, 1953 and 1956). And then Underwood & Stimson (1990) in their phylogenetic study placed all the indo-australian python species recognized at that time to a single genus Morelia, ignoring the obvious morphological differences. So, what is "consensus" then? Is it the collective loose of one's way in taxonomy and forgetting the things learned once?
> Is it a consensus today, not to use the BSC anymore because the reproductive isolation can not be tested in the wild?
Your wrote:
First, let's distinguish between species concept ("what is a species" and species diagnosis criteria ("how do we diagnose it?"
Under just about any evolutionary paradigm, a species is basically a separate evolutionary lineage. Most of the so-called "species concepts" such as the BSC are in reality centered around diagnostic criteria - the BSC simply states that reproductive compatibility is the criterion for recognising species. I think pretty much everyone would agree that reproductive isolation DOES indicate separate species status, since two lineages that cannot exchange genes are clearly evolving separately. However, lack of reproductive isolation is no loger viewed as precluding separate species status by most practicing systematists nowadays, partly because of the impossibility of relevant testing for allopatric taxa.
I do understand that it is impossible to test reproductive isolation of allopatric populations in the wild, and because of that, reproductive isolation is no longer being viewed as a creterion for speciation. Anyway, I tend to agree with Mayr (1996) that allopatric populations form incipient races and that "They may due in time aquire the needed isolating mechanisms to function as well separated species." (Mayr, 1996). So, if there is a reduced gene pool and no gen flow occurs with other popualtions, allopatric population will - under the evolutionary paradigma - also form seperate lineages, wouldn't they? It just a matter of time  The phylogenetists (?) would now perhaps argue they are not, if they have the same ancestor, but as a matter of fact, we actually all have the same ancestor. Again its only a matter of the time you look back in your historical view
If I got that right, an ancestor in the phylogenetic meaning is the one species state before there is a split-up in any major character (that's at least what the phylograms try to tell when branching).
But by agreeing to Mayr's first statement, I also have to agree that "Owing to the gradualness of the process of speciation, every incipient species at one time in its cycle goes through subspecies stage." (Mayr, 1996). Am I wrong, or would it be so, that if one follows Mayr's statements, every allopatric population would at least be recognized at sub-generic level? It's only a matter of time until they will have to be recognized as full species?
just a few thoughts
Cheers,
Wulf
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http://www.leiopython.de - the white-lipped python site -
http://www.herpers-digest.com - herp related eBooks search -
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