[Taxacom] Dispersal... again

Wed Oct 26 18:05:53 CDT 2011

Hi Dick,
?
Anthropogenic distribution?involves a phase of mobilism and range expansion. I don't think this is chance dispersal, it's more?like the great geological phases of range expansion - as in the?last great sea level maximums in the mid-Cretaceous.??As with geological phases of range expansion, anthropogenic distribution leads to repeated distribution patterns;?a common one in Australia is: Adelaide, Melbourne, Sydney, i.e. the three large cities in the south-east.?Chance dispersal ('long distance dispersal') is another process as it only involves one group at a time -?it is not due to a separate phase of history and does not?involve a?whole 'community' of taxa. For example, someone may date the New World primates at 47.5823 Ma and infer a single event that only happened once in?history. The trans-Atlantic break in hystricomorph rodents?is dated at a different time and is attributed to a different, unrelated?event.???
?
The Fragaria chiloensis pattern: Hawaii, western North America, southwestern?South America, is an intriguing one, but repeated in many groups. It is well-documented in molecular studies now, e.g. in Silene, Sanicula and the tarweeds and relatives (Madiinae). It seems to be related to the convergence of the Americas with the East Pacific rise. This has led to the?subduction of large parts of the East Pacific (including seamounts) but also the accretion of many Pacific terranes onto western America (see my 2011 Syst Biol paper on islands).
?
Michael?

Wellington, New Zealand.

My papers on biogeography are at: http://tiny.cc/RiUE0

________________________________
From: Richard Jensen <rjensen at saintmarys.edu>
To: "Weakley, Alan S" <weakley at bio.unc.edu>
Cc: Michael Heads <michael.heads at yahoo.com>; "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
Sent: Thursday, 27 October 2011 5:25 AM
Subject: Re: [Taxacom] Dispersal... again

Well....actually my question was a loaded one.? Before I get to that, I 
already knew about Thismia - there is an annual Thismia hunt to try to 
find it again.

The example I described was based on a species known only from Australia 
and from Cook County, Illinois.? Simple enough, except that the Illinois 
location was O'Hare Field, a major international airport.? The plant had 
no known taxonomic affinities in North America and the working 
hypothesis was that it hitched a ride either on the clothing of a 
passenger or on an airplane.? Perhaps an exaggerated example of 
long-distance dispersal?

I wonder about Fragaria chiloensis, a strawberry that occurs on the 
Pacific coasts of North America, in Hawai'i, and in Chile (and, I 
believe, Argentina).? This pattern has been explained by invoking 
migratory birds as vectors.? Perhaps this is one of the one-off examples 
that Michael and John have referred to.

Dick J

On 10/25/2011 10:12 PM, Weakley, Alan S wrote:
> I suspect that the Illinois - Australia situation that Dick is remembering uncertainly is the generic distribution of the mycotrophic Thismia (Thismiaceae), which is tropical (not strictly Australian) and found once, apparently a different (and presumed extinct) species, Thismia americana, in a prairie in the Chicago area in the USA.
>
> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Michael Heads
> Sent: Tuesday, October 25, 2011 10:01 PM
> To: Dick Jensen
> Cc: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Dispersal... again
>
> Hi Dick,
>? 
> My own experience is that geographic patterns can be explained with phases of range expansion (by normal dispersal, using normal means seen every day, and not involving differentiation) alternating with phases of vicariance. There is no need for a separate process of 'chance dispersal', at least for the usual patterns, but maybe it would explain genuine, one-off distributions. My first question would be: is the Australia - Illinois plant really a one-off or is there a shared pattern? (it rings a bell - is it a Cuscuta or something?). For rare distribution patterns you have to look widely, to invertebrates for example. Other questions that can be investigated: are the Australian and Illinois populations differentiated? Where are the sister group and other relatives? Perhaps the group is a relict of a Tethyan distribution - there are heaps of Australasia - Mediterranean disjunctions.? ? 
>? 
> Michael
>
> Wellington, New Zealand.
>
>
> My papers on biogeography are at: http://tiny.cc/RiUE0
>
>
> ________________________________
> From: Dick Jensen<rjensen at saintmarys.edu>
> To: John Grehan<jgrehan at sciencebuff.org>
> Cc: taxacom at mailman.nhm.ku.edu
> Sent: Wednesday, 26 October 2011 2:26 PM
> 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 _______________________________________________
>
> 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

-- 
Richard J. Jensen, Professor
Department of Biology
Saint Mary's College
Notre Dame, IN 46556
Tel: 574-284-4674