[Taxacom] Dispersal paradigm (was: Antarctic dispersal)

[JF Mate]

John, repeating Ken?s name is not going to make the duality of
biogeographical processes go away. Ken has devoted more time and
effort to try and discuss this with you than it is worth it because,
lets face it, he is keen to discuss it and you are not. So by
attrition you may silence him but it will be a pyrrhic victory. In any
case, in layman?s terms your arguments essentially are:

-Stuff disperses but not so much that it can ever compete with
vicariance. Keep it vague so it is inherentely untestable too.

-Fossils are minimum age points but I can go back as far as it is
needed to prove that, eventually, a tectonic event is there to explain
the distribution.

-Gene evolutionary rates are completely, utterly, totally random and
essentially impossible to calibrate accurately. This is important
because the key difference between dispersal and vicariance is timing.
If you eliminate the chance for timing you cannot disprove vicariance.
Ergo panbiogeography wins.

-And always use catchy adjectives to label the ?other? side and appeal
to conspiracies to lend further credence to your cause.

I find all this sad to be perfectly honest. If your argument was that
vicariance is more important than dispersal you would have broad,
almost universal agreement. As a simple numbers game it is immediately
obvious that if you split a continent in half you do the same to the
distributions of all the organisms. But it is your insistence to paint
the "other" (imaginary) side with colourful objectives that just makes
it damn annoying.

Best

Jason

On 10 June 2014 18:13, John Grehan <calabar.john at gmail.com> wrote:
> I think Ken is quite right to attribute the allure of dispersal
> explanations for evolution as a product of personal experience. Dispersal
> as an ecological phenomenon (the movement of animals and plants (seeds etc)
> is a highly visible phenomenon so it is not suprising that it has such a
> hold over explanations for vicariant (allopatric) differentiation. And
> certainly any species may spread to occupy a much larger areas, but this
> has to do with range expansion (or contraction), not differentiation.
> Obviously a widespread ancestor established its range in the first place
> through means of survival becoming means of dispersal.
>
>
> Ken may feel that ?the most vocal proponents of vicariance (since the
> acceptance of continental drift) have often overdone their backlash against
> the predominant dispersal paradigm? has not given any empirical foundation
> for such a view. This is not about a pendulum of popularity of an idea, but
> whether the idea (method, model, theory etc) works for the facts at hand.
> Dispersal models have to ignore or explain way allopatry, vicariance does
> not. Science is not about ?balanced? views for such a concept is purely
> political, not scientific. Einstein?s theory of relativity may have been an
> entirely ?unbalanced?, but it matters not a wit.
>
>
> It is not so much about disagreeing with Ken over panbiogeographic
> approaches that is of interest, but the nature of that disagreement. Ken?s
> view is based on assumptions about what is correct or not rather than on
> empirical evidence. Ken believes that fossil calibrated (or any historical
> calibration) of molecular divergence ages not minimal even though that goes
> against the facts. Panbiogeographic reconstructions are based on spatial
> analysis that recognizes the existence of allopatry being widespread among
> taxa, and that this allopatry can be correlated with tectonics that
> provides a hypothesis of an actual biogeographic age of origin. Some
> analyses show correlations with pre-drift tectonic formations, thus
> providing evidence of differentiation prior to drift taking place in
> particular regions.
>
>
>
> John Grehan
>
>
> On Mon, Jun 9, 2014 at 8:44 PM, Ken Kinman <kinman at hotmail.com> wrote:
>
>>
>>
>>
>> Hi Michael,                                                           I
>> suppose the centre of origin/dispersal view has been dominant for thousands
>> of years because humans have been able to recognize that their own species
>> is so prone to such dispersal.  And today biologists can see the evidence
>> that our species (and related species like Homo erectus) dispersed from
>> smaller areas to occupy much larger areas (eventually including the
>> Americas for Homo sapiens).  How widely we should extrapolate that to other
>> taxa is obviously debatable, but I still believe that the most vocal
>> proponents of vicariance (since the acceptance of continental drift) have
>> often overdone their backlash against the predominant dispersal paradigm.
>>       It really does far more harm than good to swing any pendulum too
>> far, and more recently we have the resulting opposing backlash of
>> dispersalists against too much vicariance.  Of course, this is not as
>> extreme as the pendulum swing which resulted in a total rejection of all
>> paraphyletic taxa (and throwing all the babies out with the bathwater), but
>> it is still problematic.  In both cases, I believe a middle ground will be
>> found that results in more balanced approaches.  In my view that means
>> pulling back a bit on the vicariance front that went too far (and easing up
>> on attacks against dispersalists), as well as accepting formal paraphyletic
>> taxa where they are most useful (thus ending a decades-long backlash
>> against all paraphyletic taxa whether they were good or bad).   In any
>> case, I disagree with your panbiogeographic approach to both ratites and
>> Order Crossosomatales, so I guess it is best to just agree to disagree on
>> how much dispersal occurred during their evolution.  I also disagree that
>> the age of the eudicot clade is nearly as problematic as you make it out to
>> be.   So it goes.
>> ---------------------------Ken
>>
>> Michael wrote:
>> Whether or not ideas are accepted or popular is interesting for sociology,
>> but is not relevant to logical, scientific argument. The centre of
>> origin/dispersal view is the dominant paradigm, and has been for thousands
>> of years, but that does not mean it's right. In any case, the eudicot age
>> is problematic (there is a whole section on it in my 2014 book (p. 67).
>>
>> ----------------------------------------------------------------------------------------------------------------------------------------------------
>>
>>
>>
>>
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