[Taxacom] Long-distance oceanic dispersal (rafting) of Nothofagus species
John Grehan
calabar.john at gmail.com
Sun Jun 3 19:49:18 CDT 2018
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:kinman 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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>
>
>
> --
> -So many mites, so little time!
> Barry M. OConnor
> Professor & Curator
> Department of Ecology & Evolutionary Biology
> Research Museums Center
> University of Michigan phone: 734-763-4354
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