[Taxacom] Long-distance oceanic dispersal (rafting) of Nothofagus species

Sun Jun 3 19:59:21 CDT 2018

Hawaii is a classic example of a biota derived mainly (exclusively?) by chance dispersal rather than vicariance, with consequent radiation of lineages into unoccupied niches. Makes sense to me!

Stephen

--------------------------------------------
On Mon, 4/6/18, John Grehan <calabar.john at gmail.com> wrote:

 Subject: Re: [Taxacom] Long-distance oceanic dispersal (rafting) of Nothofagus species
 To: "Stephen Thorpe" <stephen_thorpe at yahoo.co.nz>
 Cc: "Barry OConnor" <bmoc at umich.edu>, "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
 Received: Monday, 4 June, 2018, 12:55 PM

 Hawaii is
 a classic example of what?
 John Grehan
 On Sun, Jun 3, 2018 at 8:53
 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
 wrote:
 Evidence
 for long distance dispersal over vicariance must take into
 account entire biotas, not just selected taxa. Hawaii is the
 classic example.

 Stephen

 ------------------------------ --------------

 On Mon, 4/6/18, John Grehan
 <calabar.john at gmail.com>
 wrote:

  Subject: Re: [Taxacom] Long-distance oceanic dispersal
 (rafting) of    Nothofagus species

  To: "Barry OConnor" <bmoc at umich.edu>

  Cc: "taxacom at mailman.nhm.ku.edu"
 <taxacom at mailman.nhm.ku.edu>

  Received: Monday, 4 June, 2018, 12:49 PM

  Barry,

  An answer to your question requires a bit of a

  clarification about

  dispersal and its

  relationship to biogeographic origin of allopatric taxa

  (which is what most biogeographic controversies

  are about), although

  probably best to read

  discussion about that in a more structured account

  such as you will find in Heads' books .

  Dispersal as an ordinary ecological

  process

  is what we observe in real time. It results in survival
 of

  the

  species and may result in range

  expansion under particular circumstances.

  Differentiation of allopatric taxa requires

  isolation. If dispersal is so

  pervasive as

  to preclude isolation then there cannot be allopatric

  differentiation. This is the tangle that

  emerges when dispersal is used as

  the

  mechanism to explain biogeographic patterns of allopatry.
 A

  resolution

  of this paradox is to view

  dispersal as operative in establishing ancestral

  range rather than creating isolated entities.

  So seeing  *Anolis* lizard on

  a raft of

  hurricane debris just off a Caribbean island is
 effectively

  no

  different from seeing any other organism

  moving or moved about. It has

  immediate

  ecological significance (in terms of metapopulation
 survival

  for

  example - again characterized in more

  detail by Heads) but its

  biogeographic role

  cannot be assumed.

  John

  Grehan

  On Sun, Jun 3, 2018

  at 7:28 PM, Barry OConnor <bmoc at umich.edu>

  wrote:

  > I'm curious

  - what is *evidence* of chance dispersal other
 than, say,

  > seeing an *Anolis* lizard on a raft of

  hurricane debris just
 off a

  > Caribbean

  island? - Barry

  >

  > On

  Sun, Jun 3, 2018 at 7:08 PM, Kenneth Kinman <kinman at hotmail.com>

  wrote:

  >

  >>

  John,

  >>

  >>   

     Well, you tossing out such red herrings will not

  dissuade me.

  >> Including the

  scientific one about frogs.  The two primitive frog

  families

  >> originated way back in the

  Paleozoic when the world map was much different

  >> (Gondwanaland still largely intact). 

  No long-distance dispersal

  >>

  necessary.  Vicariance explains that case quite
 nicely. 

  Nothofagus evolved

  >> much later

  (after the break up Gondwana), so I don't know why
 you

  tossed

  >> out that red herring.   

  And comparing my hypothesis to UFOs or an Act of

  >> God could be interpreted as a bit

  insulting.  And in your second post

  >> saying that "Chance dispersal

  continues to hold a very visceral appeal for

  >> evolutionary biologists", seems

  to indicate to me that many

  >>

  panbiogeographers tend to overstate the importance of

  vicariance and too

  >> often either

  ignore or attack evidence for chance dispersal when it
 is

  >> presented.  I suspect that is what

  will happen if any evidence is found to

  >> support my hypothesis.  One thing is

  certain---we won't find such evidence

  >> if we don't look for it.

  >>

  >>         

        -------------Ken

  >>

  >> P.S.  Your latest comment about

  "fairy tales" was a bit rude.  I don't

  >> see why the explanation I put forward

  and question I asked of Bart should

  >>

  be characterized as fairy tales.

  >>

  >>

  >>

  ______________________________ __

  >>

  From: John Grehan <calabar.john at gmail.com>

  >> Sent: Sunday, June 3, 2018 9:46 AM

  >> To: Kenneth Kinman

  >> Cc: Stephen Thorpe; taxacom at mailman.nhm.ku.edu

  >> Subject: Re: [Taxacom] Long-distance

  oceanic dispersal (rafting) of

  >>

  Nothofagus species

  >>

  >> Ken,

  >>

  >> Its not a testable notion in any real

  sense any more than attributing the

  >>

  connection to UFO's. Further, it is not an
 'odd'

  distribution, but one that

  >> is very

  even (meaning standard). One can invoke any number of

  imaginary

  >> events to toss plants and

  animals from one side of the Tasman to the other,

  >> or even just place them there by an

  Act of God, but there is no empirical

  >> imperative to do so for this any more

  than imagining a tsunami to toss

  >>

  frogs from Vancouver to New Zealand.

  >>

  >> John

  Grehan

  >>

  >> On

  Sun, Jun 3, 2018 at 8:38 AM, Kenneth Kinman <kinman at hotmail.com

  >> <mailto:kinman at hotmail.com>>

  wrote:

  >> Hi Stephen,

  >>

  >>       But

  it could be somewhat scientifically testable if some

  organisms

  >> (mostly likely insects)

  have the same odd distribution in New Zealand and

  >> Tasmania (or adjacent Australia).  So

  I am hoping that some entomologist

  >>

  might know of insects that fit the bill.  And if there
 were

  more than one

  >> such organism, the

  more likely this dispersal scenario would become.

  >>

  >>       

  And note that I cited two different Nothofagus species

  groups with

  >> the same odd

  distribution (one in subgenus Lophozonia and the other
 in

  >> subgenus Fuscospora).  And those two

  dispersals could have happened at

  >>

  different times.  So that already increases the
 probability

  of dispersal.

  >> Anyway, at least Fred

  understood what I was suggesting:

  >>

  http://mailman.nhm.ku.edu/
 pipermail/taxacom/2006- December/108388.html

  >>

  >>

  >> -----------------Ken

  >>

  >>

  ______________________________ __

  >>

  From: Stephen Thorpe <stephen_thorpe at yahoo.co.nz<
 mailto:

  >> stephen_thorpe at yahoo.co.nz>>

  >> Sent: Saturday, June 2, 2018 8:59

  PM

  >> To: Kenneth Kinman

  >> Cc: taxacom at mailman.nhm.ku.edu<
 mailto:taxacom at mailman.nhm.ku.
 edu>

  >> Subject: Re: [Taxacom] Long-distance

  oceanic dispersal (rafting) of

  >>

  Nothofagus species

  >>

  >> "Could certain insects, mosses,

  or other organisms have hitched a ride on

  >> such a Nothofagus raft?"

  >>

  >> Impossible to

  rule out just about anything that doesn't
 constantly

  >> require running freshwater. If it

  happened during summer, there could be a

  >> desiccating effect, but at other times

  the amount of freshwater dampness

  >>

  could remain at acceptable levels.

  >>

  >> The problem

  though, as I see it, is that these dispersion events
 are

  >> entirely random and unpredictable, so

  it is hard to base much in the way of

  >> science on it.

  >>

  >> Stephen

  >>

  >>

  ------------------------------ --------------

  >> On Sun, 3/6/18, Kenneth Kinman <kinman at hotmail.com<mailto:kin

  >> man at hotmail.com>>

  wrote:

  >>

  >> 

  Subject: [Taxacom] Long-distance oceanic dispersal
 (rafting)

  of

  >> Nothofagus      species

  >>  To: "Kenneth Kinman"

  <kinman at hotmail.com<mailto:kin
 man at hotmail.com>>

  >>  Cc: "taxacom at mailman.nhm.ku.edu<
 mailto:taxacom at mailman.nhm.ku.
 edu>"

  <

  >> taxacom at mailman.nhm.ku.edu<
 mailto:taxacom at mailman.nhm.ku.
 edu>>

  >>

  >>  Received:

  Sunday, 3 June, 2018, 1:51 PM

  >>

  >>  Hi all,

  >>

  >>  The recent thread got me thinking

  about a debate that some

  >>  of us

  were having on taxacom almost 12 years ago.  Namely

  >>  whether long-distance oceanic

  dispersal (by rafting) was a

  >> 

  significant factor in the geographic distribution of
 some

  >>  species of Nothofagus (sensu

  lato).

  >>

  >>  

  My hypothesis was that large rafts of dislodged

  Nothofagus

  >>  trees (due to tsunami

  or other massive flooding event) could

  >>  have held some of their fruit above

  the ocean surface and

  >>  rafted from

  Tasmania to New Zealand, where one or more  new

  >>  species could evolve (due to founder

  effect).  This would

  >>  be a

  relatively short rafting event compared to the much

  >>  longer driftwood oceanic rafting

  that happened from South

  >>  America

  to Tasmania: Barber, 1959, in the journal Nature;

  >>  "Transport of Driftwood from

  South America to

  >>  Tasmania".

  Is there other evidence that such dispersal

  >>  of Nothofagus could have happened?

  Could certain insects,

  >>  mosses, or

  other organisms have hitched a ride on such a

  >>  Nothofagus raft?

  >>

  >>         

           --------------Ken Kinman

  >>  http://mailman.nhm.ku.edu/
 pipermail/taxacom/2006- December/108385.html

  >> 

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