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

JF Mate aphodiinaemate at gmail.com
Wed Jun 6 11:23:08 CDT 2018 

John,

analyzing biogeographic distributions is not very useful in the
absence of a time scale. Timing is often the only difference between
dispersal and vicariance, and all the arguments I can recall revolve
around the absolute or relative timing of splits of one lineage vs
another and/vs tectonics. That is why I think you focus so much on the
only proxy we have to complete the extremely patchy fossil record.
In the particular case of the Platyrrhini, the available evidence
suggests that the age for the group is c. 25-32mya
(https://doi.org/10.1093/molbev/msg172) and this is the most widely
accepted date (give or take but close to this range) using well
accepted molecular dating methods and fossils. You can quibble about
fossils and calibrations if the window was small enough, but the gap
is a chasm considering what you would need for the alternate scenario,
so we can only conclude, based on the available evidence at hand, that
the NW monkeys arrived there over sea and not as a result of
vicariance. Should fossils be found at a later date that push the
origin back sufficiently to consider the latter scenario then great,
but so far this is not the case. If they made it there swimming,
rafting or island-hopping (all three possible perfectably reasonable
dispersal mechanisms) is a matter of testing the ability of these
monkeys to survive each of these scenarios. None of this is a fairy
tale, pseudoscience nor an attack on vicariance.

This sort of dovetails with Michael´s often repeated question of "why
only once". My answer is because dispersal is hard, unplanned and the
chances of success slim to nil.


Jason




On 5 June 2018 at 01:00, John Grehan <calabar.john at gmail.com> wrote:
> Jason,
>
> I would suggest that the snag is not so much one side claims that molecular
> data is glorified phenetics or that dispersal is an unquantified, undefined
> amount that exists beyond the equally fuzzy "ecological dispersal". In the
> present discussion the issue has revolved around the age of extant
> Nothofagus and monkeys. In both cases the challenge presented to their being
> young was to ask for evidence. So far the response has been fossils, but
> without explaining how the present fossil record precludes Mesozoic origins
> for the taxa. There has further been the assumption that molecular dates are
> actual or absolute rather than minimal, but Ken says this is a red herring,
> I think because he was indicating that his position was not based on
> molecular divergence estimates (I may have that wrong in which Ken can
> correct).
>
> Arguments about molecular data and trees are phenetic or not is of no
> concern as far as biogeographic analysis is concerned - which can analyze
> the geographic distribution of any phylogeny.
>
> John Grehan
>
> On Mon, Jun 4, 2018 at 4:42 PM, JF Mate <aphodiinaemate at gmail.com> wrote:
>>
>> What I meant is that the topic, as far as I see it, is dead in Taxacom
>> (bar a few brave souls) since no fruitful debate is possible. The
>> discourse invariably hits the same snags:
>>
>> One side claims that molecular data is glorified phenetics with no
>> contextual value if it contradicts a particular point of
>> view/hypothesis.
>> Dispersal is an unquantified, undefined amount that exists beyond the
>> equally fuzzy "ecological dispersal".
>> More fossils can always be found.
>>
>> As for the field, what I see is that people have long moved on,
>> pursuing a hybrid model where the facts, always scarce and patchy, may
>> support one model or another, and where novel data may refute previous
>> hypotheses. In the end some things have moved (either due to luck or
>> ability) and others haven´t, but in the end every case should assume
>> that there is no de facto explanation.
>>
>> Jason
>>
>> On 4 June 2018 at 16:13, John Grehan <calabar.john at gmail.com> wrote:
>> > Jason,
>> >
>> > Not sure what you mean by 'the topic has been dead for years'. Do you
>> > mean
>> > that as far as you are concerned that there is no resolution of the
>> > different points of view and that for you the topic is dead - of no
>> > further
>> > interest to you? Certainly for biogeographers in general the topic is
>> > not
>> > dead since biogeography continues to involve active participation of
>> > many
>> > biologists. And over the last few years there have been some
>> > considerable
>> > clarity over the nature of shared biogeographic patterns and their
>> > geological correlation that are predictive (of other taxa), testable (in
>> > the
>> > sense of corroboration and also potentially future discoveries), and
>> > clear
>> > definitions that everyone can understand.
>> >
>> > The principal problem with Ken's assertion about the floating Nothofagus
>> > trees (with some upside down!) is that it is a scenario generated by
>> > imagination rather than some kind of analysis, and based on an assertion
>> > that the taxa involved evolved later than any geological separation, but
>> > this is totally without evidence, there being no fossil or calibrated
>> > molecular dates that preclude earlier origins. Same goes for his
>> > assertions
>> > about monkeys. The papers he cites simply do what Ken does, assert a
>> > belief
>> > system that monkeys rafted from one region to another, denying any
>> > possibility of earlier origin even though there is no actual evidence to
>> > do
>> > so. That is why I call such stories fairy tales. All science generates
>> > stories (even in physics). Stories are our models of explanation, but to
>> > have some integrity there must be a sequential connection to some
>> > evidence
>> > as it is the nature of evidence that can come under scrutiny and
>> > analysis
>> > and therefore be part of science. At least that is how I see it.
>> >
>> > John Grehan
>> >
>> > On Mon, Jun 4, 2018 at 6:57 AM, JF Mate <aphodiinaemate at gmail.com>
>> > wrote:
>> >>
>> >> You can´t win this Ken, that is why the topic has been dead for years.
>> >> There is a clear problem with a lack of clear, predictive and testable
>> >> hypotheses and definitions, without which advance is impossible.
>> >>
>> >> Best
>> >>
>> >> Jason
>> >>
>> >> On 3 June 2018 at 03:51, Kenneth Kinman <kinman at hotmail.com> wrote:
>> >> > 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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>> >> Nurturing Nuance while Assaulting Ambiguity for 31 Some Years,
>> >> 1987-2018.
>> >
>> >
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>> Nurturing Nuance while Assaulting Ambiguity for 31 Some Years, 1987-2018.
>
>

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