[Taxacom] NZ biogeographer's exam Q3

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Sat Jan 28 19:53:58 CST 2017


"avoiding overlap with sister taxa" could be the result of competitive exclusion. Anyway, all I'm saying is that a mixture of vicariance and dispersal is pretty obviously what actually happens.

Stephen

--------------------------------------------
On Sun, 29/1/17, John Grehan <calabar.john at gmail.com> wrote:

 Subject: Re: [Taxacom] NZ biogeographer's exam Q3
 To: "Stephen Thorpe" <stephen_thorpe at yahoo.co.nz>
 Cc: "taxacom" <taxacom at mailman.nhm.ku.edu>
 Received: Sunday, 29 January, 2017, 2:34 PM
 
 Far
 fetched or not is not the issue. It's a might or might
 not be that has no informative content. It might be the kupe
 discovered the South Island rather than the North. Inventing
 might be's to explain away tectonic correlation is like
 saying that there is no informative content to correlation
 just because the correlation may not mean anything. It might
 be sheer coincidence that marine taxa conform to the same
 distributional boundaries as terrestrial and certainly one
 might prefer that view. It might be sheer coincidence that
 species disperse by chance only to make sure somehow
 (teleology?) to avoid overlap with sister taxa - time and
 time again, taxon after taxon. The alternative explanation
 raises no such paradox.
 John
 Grehan
 On Sat, Jan 28, 2017 at
 8:02 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
 wrote:
 Chance
 dispersal is not far fetched. It is very mundane. Therefore,
 it is a priori very likely to be a big factor for species
 distributions, particularly for close adjacent
 landmasses.
 
 
 
 Stephen
 
 
 
 ------------------------------ --------------
 
 On Sun, 29/1/17, John Grehan <calabar.john at gmail.com>
 wrote:
 
 
 
  Subject: Re: [Taxacom] NZ biogeographer's exam
 Q3
 
  To: "Stephen Thorpe" <stephen_thorpe at yahoo.co.nz>
 
  Cc: "taxacom" <taxacom at mailman.nhm.ku.edu>
 
  Received: Sunday, 29 January, 2017, 1:49 PM
 
 
 
  As a
 
  separate response to Stephen suggesting patterns
 either
 
  side of the Strait "might" be the result of
 chance
 
  dispersal, I would fully agree that it might be the
 case,
 
  just as all the tectonically bounded distributions within
 NZ
 
  might be the result of chance dispersal and have no
 causal
 
  relationship, or that the biogeographic boundary at
 the
 
  MacPherson/MacLeay overlap is just the result of
 chance
 
  dispersal and has no causal relationship with the
 tectonic
 
  correlation, or that the the movement of planets might
 be
 
  the result of chance rather than Newtonian laws. I
 agree
 
  that anything might be possible, even that moas swam to
 New
 
  Zealand after the (non-existent) drowning of NZ. But
 
  'might be" is just a 'might be" which
 also
 
  means "might not be" and does not seem to get
 
  anyone very far very fast. Of course, I might be wrong
 
  :)
 
  John Grehan
 
  On Sat, Jan 28, 2017 at
 
  7:17 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
 
  wrote:
 
  On the
 
  other hand, the sea barrier might be the primary
 factor,
 
  followed by chance dispersal over the strait to the
 adjacent
 
  land on the other side (followed by limited spreading).
 
 
 
 
 
 
 
  Stephen
 
 
 
 
 
 
 
  ------------------------------ --------------
 
 
 
  On Sun, 29/1/17, John Grehan <calabar.john at gmail.com>
 
  wrote:
 
 
 
 
 
 
 
   Subject: [Taxacom] NZ biogeographer's exam Q3
 
 
 
   To: "taxacom" <taxacom at mailman.nhm.ku.edu>
 
 
 
   Received: Sunday, 29 January, 2017, 12:37 PM
 
 
 
 
 
 
 
   NZ biogeographer’s exam Q3
 
 
 
 
 
 
 
   Why is it not necessary to assume that a Cook Strait
 
 
 
   boundary in a
 
 
 
   terrestrial group is the result of the sea barrier?
 
 
 
 
 
 
 
   “It is natural to assume that a Cook Strait boundary
 in
 
  a
 
 
 
   terrestrial group
 
 
 
   is the result of the sea barrier. Yet many southern
 
  groups
 
 
 
   reach their
 
 
 
   northern limit at the *northern* side of the strait
 
  (e.g.,
 
 
 
   the cicada
 
 
 
   *Amphipsalta
 
 
 
   strepitans*; Marshell et. al., 2012). In a similar
 way,
 
  many
 
 
 
   northern
 
 
 
   groups have their southern limits at the southern
 side
 
  of
 
 
 
   the strait. For
 
 
 
   example,* Hebe parviflora* (PLantaginaceae) is
 
  widespread in
 
 
 
   the eastern
 
 
 
   North Island and has its southern limit along the
 
 
 
   northeastern shores of
 
 
 
   the South Island (Marlborough Sounds, Cape Campbell)
 
  (Bayly
 
 
 
   and Kellow,
 
 
 
   2006). These distributions indicate that it is the
 Cook
 
 
 
   Strait region – not
 
 
 
   the strait itself – that marks the phylogenetic
 
  break.
 
 
 
 
 
 
 
   In a similar pattern to that of these last,
 terrestrial
 
 
 
   groups, Ross et a.
 
 
 
   (2012) reported a Cook Strait break in the estuarine
 
 
 
   bivalve, *Austrovenus
 
 
 
   stuchburyi*, but noted that the break does not
 coincide
 
 
 
   exactly with the
 
 
 
   modern strait. Instead, northwest Nelson specimens
 belong
 
  to
 
 
 
   the North
 
 
 
   Island clade, and Wellington specimens are in the
 South
 
 
 
   Island clades.
 
 
 
   Again, the pattern suggests that the modern
 topography
 
  of
 
 
 
   the Cook Strait
 
 
 
   region is not relevant to the biogeographic
 
  break."
 
 
 
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