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

Wed Jun 6 11:52:11 CDT 2018

Jason, Many thanks for thoughtful and reflective comments. I think you have
articulated the core issues and perspectives quite well. My responses below:

“analyzing biogeographic distributions is not very useful in the absence of
a time scale.”

Perhaps, but certainly agree with desirability of estimating a temporal
dimension.

“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.”

Agreed that much of the opposition on timing comes from rejection of
tectonic correlations that are earlier than the (minimum) molecular
estimates.

“That is why I think you focus so much on the only proxy we have to
complete the extremely patchy fossil record.”

Not sure of what ‘proxy’ you refer to.

“In the particular case of the Platyrrhini, the available evidence suggests
that the age for the group is c. 25-32mya”

Actually it does not. One can only assert otherwise by the Große Lüge that
fossil calibrated molecular estimates are not minimums.

“and this is the most widely accepted date (give or take but close to this
range) using well accepted molecular dating methods and fossils.”

Meaning that most people accept the Große Lüge.

“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.”

This is “I cannot believe it” kind of argument. Many times people in the
past took this route, both science (e.g. I cannot believe that genes can
move about), military (e.g. I cannot believe that planes can sink battle
ships), and in politics (e.g. I cannot believe that Hitler could possibly
want to exterminate Jews).

How bit a gap between a molecular estimate and other predicted age is too
large? On what objective basis?

“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.”

How many millions of years earlier would be sufficient?

“rafting or island-hopping (all three possible perfectly 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.”

It’s a fairly tale in the sense that the scenario is imagined and there is
no objective criterion to investigate. It comes down to “I cannot believe
that the primates are that much older than the current (minimum) molecular
date and therefore they had to swim (or raft or whatever).

“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."

Mikes point is that time and again, for taxon after taxon, one is supposed
to believe that successful long distance dispersal occurred only once even
over the span of tens of millions of years (and often gave rise to the same
distribution patterns and patterns that also correlated with tectonics). If
one wants to believe that, then no worries. My concern is how one reaches
what one wants to believe as the decision making process interpreting the
data to hand falls within science, but what we individually or collectively
believe does not (i.e. it is actually scientifically irrelevant how many
people believe something. It might be true or it might not).

John Grehan

On Wed, Jun 6, 2018 at 12:23 PM, JF Mate <aphodiinaemate at gmail.com> wrote:

> 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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> >> >> > 1987-2018.
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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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> Nurturing Nuance while Assaulting Ambiguity for 31 Some Years, 1987-2018.
>