[Taxacom] Oceanic dispersal vs. vicariance

Sun Jun 10 21:25:20 CDT 2018

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<mailto: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<mailto: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<mailto: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<mailto: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><mailto: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><mailto: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><mailto: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><mailto: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><mailto: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><mailto: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/pipermail/taxacom/2012-January/121575.html

-------------Ken

________________________________
From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu<mailto:taxacom-bounces at mailman.nhm.ku.edu><mailto:taxacom-bounces at mailman.nhm.ku.edu<mailto:taxacom-bounces at mailman.nhm.ku.edu>>> on behalf of JF Mate <aphodiinaemate at gmail.com<mailto:aphodiinaemate at gmail.com><mailto: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