[Taxacom] Oceanic dispersal vs. vicariance

[John Grehan]

Hi Jason,

Thanks for the latest comments. I have inserted my responses below:

“ Anyway, it seems that we can all more or less agree that timing is the key
difference between both mechanisms”

In my experience I would say that what one believes about timing may
determine how vicariance proposals are accepted or not.

“ patterns in themselves can´t distinguish either mechanism, so they are not
informative in this specific instance and we can dispense with tracks and
other such pattern searching.”

Well that is your view. I hold a different view.

“The problem is that if the timing is not in agreement with the tectonic
evidence then
vicariance can no longer be a contender for the time being.”

If the timing is correct, then sure. But the timing that is usually invoked
is in the form of divergence estimatins that are minimal rather than
actual. That’s the problem clear and simple.

 This is not a rejection of vicariance but a simple observation that
the evidence
available just isn´t´t in agreement and dispersal must be considered as
likely.”

Trouble is that what is often presented as falsifying evidence is not. When
divergence stimates are presented as falsifying evidence of earlier origins
one is, whether intentional or not, presenting a große Lüge.

“is semantic footplay posing as scientific rigour. There are limitations
and these have always been acknowledged by molecular taxonomists from
the beginning,
but not to be used as an underhanded, semantic mallet to clobber dissent.”

OK. But still a problem for me.



“And therein lies the issue I have with you and Michael. Nobody is
questioning vicariance, you question dispersal.”

Very sorry about that. Problem is that biogeography leads me to question
the role of dispersal. Can’t be helped.



“So really, we only need one example of dispersal to invalidate your
epistemological
building”

No.

“It only involves the Big Lie about molecular estimates.” Quacks like a
duck and all that.”

Meaning molecular estimation quacks like a duck?



“ Neither vicariance nor dispersal are on trial here. They are both
generally accepted mechanisms (except by you two it seems)”

How they work is on trial. Panbiogeography presents evidence that
vicariance and dispersal do not work according to Darwinian assumptions.


“ The available evidence, the research on this topic, is pretty much in
agreement with Ken´s assertion.”

What evidence?


What do you bring to the table to refute this”

Refute what?


“Claiming that “One can only assert otherwise by the Große Lüge that fossil
calibrated molecular estimates are not minimums.” is pure semantics.”

A minimum is a minimum is a minimum. The semantics come in when people
misrepresent minimums as something else.


“The burden of proof is with you providing fossil evidence or a new dataset
that, when calibrated, contradicts the previous studies”.

That’s one argument. Or there are other forms of evidence such as
biogeographic correlation.



“Ken also mentions the Malagasy fauna as having recent elements that precede
its split from Gondwana, and he is correct in this regard as well.”

How so?

“There are truly ancient lineages that are vicariant but much more recent
ones that cannot have arrived by means other than dispersal (e.g. The dung
beetle fauna is a combination). “

Evidence?

“If you can provide counterfactual evidence that can be profitably
discussed then that would be great. Semantics not so much.”

Need to know your evidence first before profitable discussion.

Cheers,

John Grehan


On Tue, Jun 12, 2018 at 4:21 PM, JF Mate <aphodiinaemate at gmail.com> wrote:

> Sorry to all for dropping off the map. In particular apologies to Ken
> for leaving him steadfastly defending the fort on his own. Anyway, it
> seems that we can all more or less agree that timing is the key
> difference between both mechanisms, and in that context patterns in
> themselves can´t distinguish either mechanism, so they are not
> informative in this specific instance and we can dispense with tracks
> and other such pattern searching.
>
> So when you claim that “... much of the opposition on timing comes
> from rejection of tectonic correlations that are earlier than the
> (minimum) molecular estimates.” you are mistaken. The problem is that
> if the timing is not in agreement with the tectonic evidence then
> vicariance can no longer be a contender for the time being. This is
> not a rejection of vicariance but a simple observation that the
> evidence available just isn´t´t in agreement and dispersal must be
> considered as likely.
>
> Saying that “To me this is about as feeble as it gets with
> biogeography - that  dispersal occurred more than once but left no
> evidence. But it happened more than once for sure.” is semantic
> footplay posing as scientific rigour. There are limitations and these
> have always been acknowledged by molecular taxonomists from the
> beginning, but not to be used as an underhanded, semantic mallet to
> clobber dissent. And therein lies the issue I have with you and
> Michael. Nobody is questioning vicariance, you question dispersal. So
> really, we only need one example of dispersal to invalidate your
> epistemological building and that is pushing you to make semantics
> your arena with such choice examples as “I do not complain about
> molecular estimates of divergence, I only complain about minimums
> being misrepresentated as actual or maximal. There is a difference!”
> or “It only involves the Big Lie about molecular estimates.” Quacks
> like a duck and all that.
>
> You also try to distract the argument by introducing other groups that
> were not part of the initial discussion. Neither vicariance nor
> dispersal are on trial here. They are both generally accepted
> mechanisms (except by you two it seems) and the only question
> originally posed was, which had a hand in the Platyrrhini, so let´s go
> back to the Platyrrhini. The available evidence, the research on this
> topic, is pretty much in agreement with Ken´s assertion. What do you
> bring to the table to refute this. Claiming that “One can only assert
> otherwise by the Große Lüge that fossil calibrated molecular estimates
> are not minimums.” is pure semantics. The burden of proof is with you
> providing fossil evidence or a new dataset that, when calibrated,
> contradicts the previous studies.
>
> Ken also mentions the Malagasy fauna as having recent elements that
> precede its split from Gondwana, and he is correct in this regard as
> well. There are truly ancient lineages that are vicariant but much
> more recent ones that cannot have arrived by means other than
> dispersal (e.g. The dung beetle fauna is a combination). That is my
> bit of evidence. If you can provide counterfactual evidence that can
> be profitably discussed then that would be great. Semantics not so
> much.
>
> Have a good one.
>
> On 11 June 2018 at 05:26, John Grehan <calabar.john at gmail.com> wrote:
> > Hi Ken,
> >
> > My comments below.
> >
> >   “ I've been reading a variety of papers on the debate (beginning about
> > 2005) between Alan de Queiroz (and others) on the one hand and Michael
> > Heads (and others, incl. John Grehan) on the other.  I have come to the
> > conclusion that both sides represent polar opposites in the debate
> between
> > oceanic dispersal and vicariance.  The truth is probably somewhere in
> > between, meaning that both sides are right about some cases, but wrong in
> > others.  Not at all surprising. “
> >
> >
> >
> > There is no evidence that the ‘truth’ is ‘probably’ somewhere inbetween.
> >
> >
> >
> > “ Perhaps the strongest case for a large number of oceanic dispersals is
> > probably from the African mainland to Madagascar. “
> >
> >
> >
> > What is the purported evidence?
> >
> >
> >
> > “but there is apparently evidence that some of those dispersals were
> along
> > island chains that no longer exist.”
> >
> >
> >
> > What is the purported evidence?
> >
> >
> >
> > “Whether such islands existed or not,”
> >
> >
> >
> > Then there is no actual evidence?
> >
> >
> >
> > “the debate between the two sides seems to be largely centered on
> molecular
> > estimates of divergence (about which Grehan seems to repeatedly complain
> ad
> > nauseum). “
> >
> >
> >
> > That comes across as a misrepresentation (unintentional I am sure). I do
> > not complain about molecular estimates of divergence, I only complain
> about
> > minimums being misrepresentated as actual or maximal. There is a
> difference!
> >
> >
> >
> > “Therefore, my increasing reluctance to respond to his continued
> "baiting".
> >
> >
> >
> > ????
> >
> >
> >
> > “ If he wants evidence, there is lots of evidence in the literature from
> > many authors (many who seem to be somewhat more objective than Alan de
> > Queiroz).  “
> >
> >
> >
> > Then state what is the purported evidence. No good just saying so.
> >
> >
> >
> >  “The case for oceanic dispersal from Australia (including Tasmania) to
> New
> > Zealand is admittedly even more controversial.  That controversy not only
> > involves molecular estimates of divergence,”
> >
> >
> > It only involves the Big Lie about molecular estimates.
> >
> >
> >
> > “but also whether or not New Zealand was completely submerged at some
> time
> > in the mid Cenozoic.”
> >
> >
> >
> > This never had legs to begin with and has been generally buried by
> > geologists and even orthodox biogeographers.
> >
> >
> >
> > “ Therefore, I am  playing devil's advocate in suggesting how one or two
> > species of Nothofagus could have rafted from Tasmania to New Zealand in
> the
> > middle of the Cenozoic.  Maybe they did and maybe they didn't, but both
> > possibilities should be kept in mind. “
> >
> > If there is evidence for rafting then sure, consider it.
> >
> >
> >
> > “Given the long-standing debate between Alan de Queiroz and Michael
> Heads,
> > I find the Nothofagus case the most challenging (even though some earlier
> > Nothofagus dispersals seem likely to have been due to vicariance over
> land
> > in Gondwana).”
> >
> >
> >
> > Nothofagus is not a ‘Gondwana’ group.
> >
> >
> >
> > “Nothofagus distribution could be due to a combination of both vicariance
> > and some cases of more recent oceanic dispersal.”
> >
> > Or not. But panbiogeography shows clearly that such a combination does
> not
> > have to be invented.
> >
> >
> > John Grehan
> >
> >
> > On Sun, Jun 10, 2018 at 10:25 PM, Kenneth Kinman <kinman at hotmail.com>
> wrote:
> >
> >> Hi all,
> >>
> >>        I've been reading a variety of papers on the debate (beginning
> >> about 2005) between Alan de Queiroz (and others) on the one hand and
> >> Michael Heads (and others, incl. John Grehan) on the other.  I have
> come to
> >> the conclusion that both sides represent polar opposites in the debate
> >> between oceanic dispersal and vicariance.  The truth is probably
> somewhere
> >> in between, meaning that both sides are right about some cases, but
> wrong
> >> in others.  Not at all surprising.
> >>
> >>        Perhaps the strongest case for a large number of oceanic
> dispersals
> >> is probably from the African mainland to Madagascar.  And the case for
> >> numerous oceanic dispersals between the African mainland and South
> America
> >> (when they were closer together) is more controversial, but there is
> >> apparently evidence that some of those dispersals were along island
> chains
> >> that no longer exist.  Whether such islands existed or not, the debate
> >> between the two sides seems to be largely centered on molecular
> estimates
> >> of divergence (about which Grehan seems to repeatedly complain ad
> >> nauseum).  Therefore, my increasing reluctance to respond to his
> continued
> >> "baiting".  If he wants evidence, there is lots of evidence in the
> >> literature from many authors (many who seem to be somewhat more
> objective
> >> than Alan de Queiroz).
> >>
> >>        The case for oceanic dispersal from Australia (including
> Tasmania)
> >> to New Zealand is admittedly even more controversial.  That controversy
> not
> >> only involves molecular estimates of divergence, but also whether or not
> >> New Zealand was completely submerged at some time in the mid Cenozoic.
> >> Therefore, I am  playing devil's advocate in suggesting how one or two
> >> species of Nothofagus could have rafted from Tasmania to New Zealand in
> the
> >> middle of the Cenozoic.  Maybe they did and maybe they didn't, but both
> >> possibilities should be kept in mind.  Given the long-standing debate
> >> between Alan de Queiroz and Michael Heads, I find the Nothofagus case
> the
> >> most challenging (even though some earlier Nothofagus dispersals seem
> >> likely to have been due to vicariance over land in Gondwana).
> Nothofagus
> >> distribution could be due to a combination of both vicariance and some
> >> cases of more recent oceanic dispersal.
> >>
> >>                                    ------------------Ken
> >>
> >>
> >> ------------------------------
> >> *From:* John Grehan <calabar.john at gmail.com>
> >> *Sent:* Thursday, June 7, 2018 10:08 AM
> >> *To:* Kenneth Kinman
> >> *Cc:* Michael Heads; Taxacom
> >> *Subject:* Re: Oceanic dispersal (rafting) of mammals in particular
> >>
> >>
> >> Hi Ken,
> >>
> >>
> >> Thanks for your latest observations on the subjects. Some reflections
> >> below.
> >>
> >>
> >>
> >>       “I do not object to vicariance (it explains many distribution
> >> patterns).  I just think panbiogeographers tend to overdo vicariance,
> and
> >> you in particular have a tendency to start ranting when vicariance is
> >> challenged in some cases.  So I probably won't be doing any more posts
> on
> >> the subject.”
> >>
> >>
> >>
> >> No problem with that. All counter responses may be viewed that way. That
> >> is why I have said that what is important is how a particular view is
> >> connected to the evidence and the nature of that evidence. And why
> should I
> >> not 'rant' when vicariance is challenged? Is that not the nature of
> science
> >> in general? I suppose one could ignore alternative views and that also
> is a
> >> choice scientists often make (at least in evolutionary biology).
> >>
> >>
> >>
> >>      “I will just close by saying that there seems to be a pattern of
> >> Africa to South America transoceanic dispersal which also includes
> >> caviomorph rodents, the hoatzin, and lots of different small reptiles
> >> (amphisbaenians, geckos, skinks, lizards, and blind snakes).  So the New
> >> World monkeys would not be an isolated case.”
> >>
> >>
> >>
> >> So you keep saying. And I keep asking for your to explicitly state the
> >> nature of the evidence, which you keep avoiding. I have no problem with
> >> your presenting your view as we are all entitled to that, but to avoid
> >> making a reasoned argument as to the nature of the evidence and how that
> >> indicates your model and falsifies other evidence of  vicariance is
> >> problematic to say the least. It is as if you are trying to protect your
> >> 'evidence' from external scrutiny (which again is the nature of being
> >> scientific). If your view is so strongly supported by evidence I would
> >> have thought you would have no such trouble in presenting that evidence
> –
> >> i.e. explicitly stating the nature of the evidence and how it
> necessarily
> >> means that vicariance evidence is not real evidence. I get the
> impression
> >> that chance dispersal is so obvious to you that you decline to provide
> the
> >> supporting evidence and have little patience with your viewpoint being
> >> challenged.
> >>
> >>
> >>
> >> As you know, I have analyzed some lizard patterns attributed to
> >> trans-oceanic dispersal and shown in detail that in these cases there
> is no
> >> actual evidence of dispersal and that the patterns conform to a process
> of
> >> allopatric differentiation. My arguments and evidence may be contested
> >> (which is fine by me), but at least I present the nature of evidence
> for my
> >> views in considerable detail.
> >>
> >>
> >>
> >> “There are presumably lots of invertebrates and plants that also show
> this
> >> pattern, but I don't have the time to delve into that.”
> >>
> >>
> >>
> >> No worries, since more assertions of your model would not add anything
> in
> >> the absence of evidence.
> >>
> >>
> >>
> >> “Vicariance does explain lots of Africa-South America relationships,
> but I
> >> still think it needs to be challenged in some cases.”
> >>
> >>
> >>
> >> Challenging vicariance is fine, but it needs evidential argument, not
> just
> >> assertions or, as in the literature, misrepresentations of the fossil
> >> record of calibrated molecular estimates.
> >>
> >>
> >>
> >> “Anyway, if you want answers to all your questions about such
> hypotheses,
> >> you should stop calling the answers fairy tales.  I was not surprised
> when
> >> Jason said: "None of this is a fairy tale, pseudoscience nor an attack
> on
> >> vicariance."
> >>
> >>
> >>
> >> I can stop calling them fairly tales when they are sequentially
> connected
> >> to evidence and that evidence is shown to falsify vicariance. At this
> point
> >> all I see are assertions without evidence, or artificially created
> evidence
> >> (molecular divergence that is not correctly presented as minimums).
> >> Actually whether I consider them fairly tales or not is neither here nor
> >> there. Some critics have characterized panbiogeographic reconstructions
> in
> >> a similar manner. It does not matter. In science (as I understand it)
> the
> >> issue is always about the presentation and nature of what constitutes
> >> evidence. This seems to me to be as true for a laboratory experiment as
> >> it does for historical reconstruction.
> >>
> >>
> >>
> >> John Grehan
> >>
> >>
> >> On Thu, Jun 7, 2018 at 9:31 AM, Kenneth Kinman <kinman at hotmail.com>
> wrote:
> >>
> >> John,
> >>
> >>       I do not object to vicariance (it explains many distribution
> >> patterns).  I just think panbiogeographers tend to overdo vicariance,
> and
> >> you in particular have a tendency to start ranting when vicariance is
> >> challenged in some cases.  So I probably won't be doing any more posts
> on
> >> the subject.
> >>
> >>       I will just close by saying that there seems to be a pattern of
> >> Africa to South America transoceanic dispersal which also includes
> >> caviomorph rodents, the hoatzin, and lots of different small reptiles
> >> (amphisbaenians, geckos, skinks, lizards, and blind snakes).  So the New
> >> World monkeys would not be an isolated case.  There are presumably lots
> of
> >> invertebrates and plants that also show this pattern, but I don't have
> the
> >> time to delve into that.
> >>
> >>      Vicariance does explain lots of Africa-South America relationships,
> >> but I still think it needs to be challenged in some cases.  Anyway, if
> you
> >> want answers to all your questions about such hypotheses, you should
> stop
> >> calling the answers fairy tales.  I was not surprised when Jason said:
> >> "None of this is a fairy tale, pseudoscience nor an attack on
> vicariance."
> >>
> >>                             ------------------Ken
> >>
> >>
> >> ------------------------------
> >> *From:* John Grehan <calabar.john at gmail.com>
> >> *Sent:* Wednesday, June 6, 2018 10:04 PM
> >> *To:* Kenneth Kinman
> >> *Cc:* Michael Heads; Taxacom
> >> *Subject:* Re: [Taxacom] Oceanic dispersal (rafting) of mammals in
> >> particular
> >>
> >>
> >> Ken,
> >>
> >> What I interpret from your position is that when you think a
> distribution
> >> arose by chance dispersal then dispersal explains how they got there,
> and
> >> if dispersal occurred more than once and did not succeed we will have no
> >> evidence of it. And allopatry is due to competitive exclusion and
> sympatry
> >> is explained as the lack of competitive exclusion. All of this is fine
> as
> >> assertions of your personal belief and there is no falsifying that.
> What is
> >> at issue, is how you reach the dispersal conclusion in the first place,
> and
> >> for both NW primates and Nothofagus you have not explained that.
> >>
> >> Jason makes the argument that if a vicariance event to 'too much'
> earlier
> >> than the oldest fossil then it cannot be believed. I don’t know if that
> is
> >> your position or if this is your reasoning for Nothofagus and Primates.
> >> Perhaps you would be so good as to make an explicit statement on that?
> It
> >> would go a long way to clearing up the otherwise confusing nature of
> your
> >> objections to vicariance. I realize that you do not publish on
> >> biogeographic method and reasoning, but it might be helpful in general
> to
> >> better understand how your views are connected to empirical sources
> since
> >> many others may share your particular perspective.
> >>
> >> John Grehan
> >>
> >>
> >> On Wed, Jun 6, 2018 at 9:18 PM, Kenneth Kinman <kinman at hotmail.com>
> wrote:
> >>
> >>
> >>      Well, competition between primate groups in Madagascar and America
> >> would have only been the deciding factor if there were later oceanic
> >> dispersals, as in Madagascar after lemurs had become so
> well-established in
> >> many different ecological niches.  Either way (later dispersals or not),
> >> the lack of overlap is primarily due to the ocean barriers which are
> very
> >> difficult to cross.  Without ocean barriers, overlap seems to be
> primarily
> >> due to noctural vs. diurnal.
> >>
> >>
> >>      It is somewhat similar in the case of Carnivora.  In Madagascar you
> >> only have Family Eupleridae, and any subsequent dispersals of the
> related
> >> Family Herpestidae would have been prevented by competitive exclusion.
> >> Elsewhere, the Herpestidae can overlap geographically with Viverridae,
> >> because Herpestids are primarily terrestrial and diurnal, while
> Viverrids
> >> are primarily arboreal and nocturnal.
> >>
> >>                      -------------Ken
> >>
> >> ________________________________
> >> From: Michael Heads <m.j.heads at gmail.com>
> >> Sent: Wednesday, June 6, 2018 7:28 PM
> >> To: Kenneth Kinman
> >> Cc: Taxacom
> >> Subject: Re: [Taxacom] Long-distance oceanic dispersal (rafting) of
> >> Nothofagus species
> >>
> >> you explain the lack of overlap between the two primate clades in
> >> Madagascar and America by competition, but the overlap in Africa and
> Asia
> >> by a lack of competition. How does that work?
> >>
> >> On Thu, Jun 7, 2018 at 11:59 AM, Kenneth Kinman <kinman at hotmail.com
> >> <mailto:kinman at hotmail.com>> wrote:
> >>
> >> Michael,
> >>
> >>       (1) I've already explained the probable reason that Haplorhines
> are
> >> absent from Madagascar.   Lemur ancestors got their first, radiated into
> >> all the available niches (which are quite varied), and competitive
> >> exclusion would have prevented any later haplorhine dispersals from
> >> becoming established (if there were any).
> >>
> >>      (2) The same is probably true for the absence of Strepsirrhines
> from
> >> America.  Haplorhines just dispersed there first.
> >>
> >>      (3)  And finally, the overlap of the two groups in much of Africa
> and
> >> Asia is probably because where they do overlap geographically, the
> >> Strepsirrhines are usually noctural and the Haplorhines are usually
> >> diurnal.  The only times they might be active at the same time would be
> >> around dusk and dawn.
> >>
> >>                       ----------------Ken
> >>
> >> P.S.  As for the two butterfly sister groups, butterflies wouldn't be
> >> killing rival intruders coming into their territories.  Primates on the
> >> other hand can be quite vicious if a rival competitor invades their
> >> territory.  The same is true for Carnivora.
> >>
> >> ________________________________
> >> From: Michael Heads <m.j.heads at gmail.com<mailto:m.j.heads at gmail.com>>
> >> Sent: Wednesday, June 6, 2018 5:49 PM
> >> To: Kenneth Kinman; Taxacom
> >>
> >> Subject: Re: [Taxacom] Long-distance oceanic dispersal (rafting) of
> >> Nothofagus species
> >>
> >> How do you explain the example I mentioned - two butterfly sister groups
> >> with partial overlap? This is a very common type of pattern.
> >>
> >> The monkeys (discussed at length in my 'Tropics' book and in Zool.
> >> Scripta.  39: 107. 2010) are another example of this:
> >>
> >> Haplorhines (monkeys etc.): America, Africa, Asia (not Madagascar).
> >> Strepsirrhines (lemurs etc.): Africa, Madagascar, Asia (not America).
> >>
> >> Competitive exclusion doesn't explain the absences in America and
> >> Madagascar, as the two groups overlap extensively through Africa and
> Asia.
> >> [https://ssl.gstatic.com/ui/v1/icons/mail/images/cleardot.gif]
> >>
> >> On Thu, Jun 7, 2018 at 10:25 AM, Michael Heads <m.j.heads at gmail.com
> >> <mailto:m.j.heads at gmail.com>> wrote:
> >> How do you explain the example I mentioned - two butterfly sister groups
> >> with partial overlap? This is a very common type of pattern.
> >>
> >> The monkeys (discussed at length in my 'Tropics' book and in Zool.
> >> Scripta.  39: 107. 2010) are another example of this:
> >>
> >> Haplorhines (monkeys etc.): America, Africa, Asia (not Madagascar).
> >> Strepsirrhines (lemurs etc.): Africa, Madagascar, Asia (not America).
> >>
> >> Competitive exclusion doesn't explain the absences in America and
> >> Madagascar, as the two groups overlap extensively through Africa and
> Asia.
> >>
> >> On Thu, Jun 7, 2018 at 9:58 AM, Kenneth Kinman <kinman at hotmail.com
> <mailto:
> >> kinman at hotmail.com>> wrote:
> >>
> >>        Competitive exclusion as it relates to oceanic dispersal does not
> >> have to be between groups that are that closely related.  It perhaps
> >> explains why there are no monkeys in Madagascar.  The lemur ancestor
> >> dispersed to Madagascar first.  If any monkeys dispersed to Madagascar
> >> later, they would have found all their niches filled by well-established
> >> lemurs.
> >>
> >>      And likewise, lemurs may have dispersed back into mainland Africa,
> >> but if they did, they would have found their niches already filled by
> >> monkeys.  So many monkeys that the lemur invaders would probably be
> killed
> >> by them.
> >>
> >>      So your question "why only once" is answered.  It probably wasn't
> >> only once.  There are probably lots of cases with multiple dispersals
> of a
> >> group, but only the first to disperse became well-established, and small
> >> numbers of later dispersers simply died very soon after arriving.  They
> >> would have left no evidence of their dispersal.
> >>
> >>                 ---------------Ken
> >>
> >> ________________________________
> >> From: Michael Heads <m.j.heads at gmail.com<mailto:m.j.heads at gmail.com>>
> >> Sent: Wednesday, June 6, 2018 4:18 PM
> >> To: Kenneth Kinman
> >> Cc: Taxacom
> >>
> >> Subject: Re: [Taxacom] Long-distance oceanic dispersal (rafting) of
> >> Nothofagus species
> >>
> >> the competitive exclusion idea only works if the clades are allopatric.
> In
> >> many cases two groups overlap in large parts of their range. For
> example,
> >> the Polyura 'eudamippus  group' of butterflies: China to Sumatra and
> >> Borneo; P.  'pyrrhus group':Sumatra (not Borneo) to SE Australia and
> Fiji.
> >> The two groups overlap through Sumatra.
> >>
> >> On Thu, Jun 7, 2018 at 5:26 AM, Kenneth Kinman <kinman at hotmail.com
> <mailto:
> >> kinman at hotmail.com>> wrote:
> >>
> >>
> >> Hi Jason,
> >>
> >>        Excellent post.  Regarding Michael's "why only once" argument, I
> >> would only add that I have provided another explanation in a post back
> in
> >> 2012.  Namely: competitive exclusion, where the first dispersal is so
> >> successful that it fills all the niches for that animal or plant.  If
> >> another dispersal happens millions of years later, they usually can't
> >> compete with the already well-established populations of its relative.
> >>
> >>       Here is a quote from the end of my posting on 01 January 2012:
> >>
> >> "In view of John's criticisms, it should be remembered that dispersal
> >> ability certainly does not ensure that oceanic dispersals will be
> >> successful in most cases. Being able to disperse long distances is only
> the
> >> first step, but lack of suitable habitat, and more importantly
> competitive
> >> exclusion by other taxa already well-established, are obviously
> barriers to
> >> even good dispersers being automatically spread geographically. Such
> >> arguments against dispersalist hypotheses are therefore unconvincing
> >> (perhaps simple, but perhaps too often simplistic)."
> >>
> >> Here's a weblink to that post: http://mailman.nhm.ku.edu/pipe
> >> rmail/taxacom/2012-January/121575.html
> >>
> >>
> >> -------------Ken
> >>
> >>
> >> ________________________________
> >> From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu<mailto:
> taxacom-bounces at m
> >> ailman.nhm.ku.edu>> on behalf of JF Mate <aphodiinaemate at gmail.com<
> mailto:
> >> aphodiinaemate at gmail.com>>
> >> Sent: Wednesday, June 6, 2018 11:23 AM
> >> To: Taxacom
> >> Subject: Re: [Taxacom] Long-distance oceanic dispersal (rafting) of
> >> Nothofagus species
> >>
> >> 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
> >>
> >>
> >>
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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.
>