[Taxacom] another biogeographic note for those interested

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Wed Nov 30 21:59:18 CST 2016

>Vicariance does not impose this kind of contradiction<
I think "contradiction" is way too strong a word (actually, it is incorrect, there is no "contradiction"!)

>it's not just one island or archipelago that is involved in each taxon, but sometimes several<
But couldn't a species disperse from island to island?

My explanation for why each satellite only has one species is that it is small and has moved further away from the center subsequent to the dispersal event, making further dispersal harder and harder.


On Thu, 1/12/16, John Grehan <calabar.john at gmail.com> wrote:

 Subject: Re: [Taxacom] another biogeographic note for those interested
 To: "Stephen Thorpe" <stephen_thorpe at yahoo.co.nz>
 Cc: "taxacom" <taxacom at mailman.nhm.ku.edu>
 Received: Thursday, 1 December, 2016, 4:49 PM
 One could
 indeed invoke any kind of dispersal, but again one would
 have to invoke great distances and yet only in ways that
 precluded overlap other than the single center of sympatry.
 Vicariance does not impose this kind of contradiction. And
 with respect to 'satellites' it's not just one
 island or archipelago that is involved in each taxon, but
 sometimes several. So again, one requires that dispersal
 went off in different directions for each taxon, went a very
 long way (sometimes halfway across the Pacific) and to
 multiple islands, but somehow not the same islands as the
 other taxa.
 On Wed, Nov 30, 2016 at
 10:41 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
 Why can't dispersal go in both directions? If the
 "center of sympatry" is a big area, whereas the
 satellites are small areas, then dispersal back from a
 satellite to the center is more likely than dispersal in the
 other direction of more than one species to any one small
 satellite. So we could start with one species in the center
 which disperses to each of the satellites independently,
 speciates on each satellite, and then each new species
 disperses back to the center creating sympatry at the
 center. If this is combined with tectonic events causing the
 distance between center and satellites to increase over
 time, then it will become less likely that any species which
 disperses back to the center will be able to subsequently
 disperse to another satellite, maintaining allopatry between
 ------------------------------ --------------
 On Thu, 1/12/16, John Grehan <calabar.john at gmail.com>
  Subject: [Taxacom] another biogeographic note for those
  To: "taxacom" <taxacom at mailman.nhm.ku.edu>
  Received: Thursday, 1 December, 2016, 4:22 PM
  Star vicariance represents a
  significant biogeographic pattern and process
  that is either generally overlooked, or explained away
  dispersal from a
  common center of origin. Star vicariance is exemplified by
  pattern of
  distributions that are largely or entirely allopatric
  for a common
  center of sympatry, giving the appearance of a
  star (depending
  on the number of taxa involved).
  Dispersal explanations attribute the region of sympatry as
  center of
  origin from which each of the taxa spread out. The
  with this view
  is that it does not explain why each taxon managed to
  so far and
  wide and yet keep out of each other’s ‘territory’
  other than the region of
  sympatry. Vicariance does not impose this quandary, but
  recognizes that the
  allopatry is the result of vicariance of a multitude of
  subsequently underwent local dispersal resulting in
  in a
  relatively localized area. Sympatry is effectively
  of dispersal.
   In “Biogeography and Evolution in New Zealand”
  draws attention to
  star vicariance with respect to several taxa, including
  very nice example
  in the plant genus Astelia which has two main clades
  the Indian and
  Pacific basins respectively. The Pacific group forms a
  pattern with
  New Zealand at the center. Even though the overlap of
  individual ranges
  looks complex against present day geography, it is
  to offer
  reconstructions of the possible ancestral range of each
  member group prior
  to the dispersal that led to the present day overlap.
  Even though the examples are presented for New Zealand,
  star pattern
  could apply to any region of the globe and as such should
  a pattern that
  any student of biogeography could recognize. At the
  least it would not
  be unreasonable for recognition of star vicariance to be
  standard exam
  question for graduate students (or any students for
  matter). I’m have
  not seen star vicariance presented in any university
  biogeography text
  book, but admittedly I have not read every one that is
  there. However,
  it goes without saying that “Biogeography and Evolution
  New Zealand”
  should be considered as a standard university text book
  biogeography course anywhere.
  John Grehan
  Taxacom Mailing List
  Taxacom at mailman.nhm.ku.edu
  The Taxacom Archive back to 1992 may be searched at: http://taxacom.markmail.org
  Injecting Intellectual Liquidity for 29 years.

More information about the Taxacom mailing list