[Taxacom] Dispersal... again

[John Grehan]

If one believes in a theoretical notion informing empirical data rather than the other way around, then yes, otherwise no.
 
How else? - From a formerly widespread ancestor.
 
John Grehan

________________________________

From: Dick Jensen [mailto:rjensen at saintmarys.edu] 
Sent: Tuesday, October 25, 2011 9:27 PM
To: John Grehan
Cc: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Dispersal... again



Does dispersal ever play a role in understanding geographic patterns?  This should be a simple yes/no question because there must be some patterns that are most readily (and scientifically) explained by dispersal.  I recall, from years ago, hearing a report of a plant species (I don't recall what it was) that was known to occur in two places in the world - Australia (where it was common) and Cook County, Illinois (where it was quite rare).  The only logical explanation was long-distance dispersal.  How else?

 

Dick J



________________________________

From: "John Grehan" <jgrehan at sciencebuff.org>
To: taxacom at mailman.nhm.ku.edu
Sent: Tuesday, October 25, 2011 9:10:15 PM
Subject: Re: [Taxacom] Dispersal... again

To my way of thinking the 'endless' discussion is not about vicariance vs dispersal, but about the assumptions that most biogeographers have, and continue to make about using Darwin's theory of center of origin and means of dispersal to understand the spatial structure of life rather than analyzing the spatial structure of life to derive an understanding about the role of means of dispersal in the origin of geographic differentiation.

To play the worn our record again, dispersal is very popular among biogeographers because most biogeographers are not interested in analyzing the spatial structure of differentiated entities and getting to know the tedious details of distribution (tedious because they are so often repetitive). With centers of origin and dispersal one is freed up from reading the records of life to make up whatever center of origin and dispersal story for an individual group or situation without having to worry about those nagging spatial incongruities.

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Frederick W. Schueler
Sent: Tuesday, October 25, 2011 4:18 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Dispersal... again

On 10/25/2011 3:47 PM, Michael Heads wrote:
>
> You wrote: '...vicariance (allopatry in Mayr?s parlance...'.  For Mayr, allopatry was not caused by vicariance, but by chance dispersal.

* sometimes it was, and sometimes it wasn't - reread "Animal Species and Evolution."

This endless vicariance versus dispersal discussion reminds me of the "are populations regulated density dependently or density-independently?" controversy of the 1960s which, faded away when it turned out that sometimes they were, and sometimes they weren't.

fred schueler.
------------------------------------------------------------
          Frederick W. Schueler & Aleta Karstad Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm Mudpuppy Night in Oxford Mills - http://pinicola.ca/mudpup1.htm Daily Paintings - http://karstaddailypaintings.blogspot.com/
     RR#2 Bishops Mills, Ontario, Canada K0G 1T0
   on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
    (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/
------------------------------------------------------------
------------------------------------------------------------

_______________________________________________

Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu
http://mailman.nhm.ku.edu/mailman/listinfo/taxacom

The Taxacom archive going back to 1992 may be searched with either of these methods:

(1) by visiting http://taxacom.markmail.org

(2) a Google search specified as:  site:mailman.nhm.ku.edu/pipermail/taxacom  your search terms here

_______________________________________________

Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu
http://mailman.nhm.ku.edu/mailman/listinfo/taxacom

The Taxacom archive going back to 1992 may be searched with either of these methods:

(1) by visiting http://taxacom.markmail.org

(2) a Google search specified as:  site:mailman.nhm.ku.edu/pipermail/taxacom  your search terms here