[Taxacom] Yoder, dispersal, and Madagascar's biota

[Ken Kinman]

Hi John,
         Perhaps the fiction is actually your imagining the existence of Jurassic primates and early Cretaceous rodents and carnivorans, etc., for which there is not a shred of fossil evidence.  And even molecular evidence would have to be stretched considerably to get the origins of such taxa back far enough to make vicariance a possibility for their presence on Madagascar.  But now that we know what the ankles of Purgatorius looked like, perhaps you will have better luck finding some of the Jurassic and Cretaceous plesiadapiforms and primates which you and Michael imagine to exist.                                                                                                          In any case, I don't think you realize how devastating the K-T extinction event was to the biota of Madagascar, and how that cleared the way for the vertebrate dispersers during the Cenozoic.  Sure, some fish and turtles apparently made it through that extinction on Madagascar, but most vertebrates didn't.                                    
         In spite of the growing amounts of evidence for Cenozoic dispersal (for invertebrates and plants, as well as vertebrates), you always retreat to your fallback position complaining about "minimal estimates", but your imagined "maximal estimates" would often have to be so old that they seem even more problematic.   Perhaps there was more Cenozoic vicariance in Australasia, but if you keep on harping about dispersal to Madagascar, it makes people wonder if you are also exaggerating the role of vicariance elsewhere.                                                -----------------Ken Kinman                                                                                    
Date: Mon, 24 Mar 2014 10:46:40 -0400
Subject: Re: [Taxacom] Yoder, dispersal, and Madagascar's biota
From: calabar.john at gmail.com
To: kinman at hotmail.com
CC: m.j.heads at gmail.com; taxacom at mailman.nhm.ku.edu

Ken,
The "overwhelming" evidence is a fiction based on the misrepresentation of minimal estimates as actual or maximal.
In what way as the review "narrow and unfair"?

It might be worthwhile for you to read Heads' assessment of relaxed molecular analysis.

Your assertion that "it stretches credibility to suggest that fossil calibration is a problem with so many of them dispersing" is problematic because their 'dispersing' is based on the calibration problem.

Ai and Huber did not demonstrate overwater dispersal by carnivores and rodents.

John Grehan


On Mon, Mar 24, 2014 at 9:45 AM, Ken Kinman <kinman at hotmail.com> wrote:



Michael and John,

      Well, the funny thing is that I was inclined to give you the benefit of the doubt on cichlids (as was Yoder and Nowak), but I am now actually less inclined to do so.   I would like to emphasize the last two sentences of Yoder and Nowak's abstract:   "For those studies that include divergence time analysis, we find an overwhelming indication of Cenozoic origins for most Malagasy clades. We conclude that most of the present-day biota of Madagascar is comprised of the descendents of Cenozoic dispersers, predominantly with African origins."   I think that their use of the word "overwhelming" is important to note, and I found no reason to think that they were exaggerating in doing so.  As for the cichlids in particular, in the text they admit that among the vertebrates, "the cichlid fishes of Madagascar represent the most challenging puzzle for differentiating vicariance from dispersal."   And then they are careful to give the arguments either way.  I thought it was a very thoughtful and balanced review, and how Michael dismisses the included studies as ONLY showing the importance of calibration method has me scratching my head in disbelief.  I think that it is a narrow and unfair assessment of the Yoder and Nowak review and of the studies they were reviewing.                                                                            It's too bad Michael (in 2012) obviously didn't have the more recently published and thorough study on the subject of cichlid biogeography, which concluded that it was dispersal, not vicariance, which produced the present distribution of those fishes:   Title: Molecular and fossil evidence place the origin of cichlid fishes long after Gondwanan rifting.    by Matt Friedman, Benjamin P. Keck, et al., 2013.    They state:  "It is important to note that our relaxed-molecular-clock analysis shares no palaeontological data in common with either our analysis of the distribution of cichlid-bearing fossil horizons or our database of outgroup-based age constraints. We interpret the convergence of these three semi-independent approaches, which all deliver age estimates for cichlids that are within error of one another, as a consequence of genuine evolutionary signal that strongly contradicts the time scales for cichlids demanded by hypotheses of Gondwanan vicariance."


        And even if one doesn't agree with Friedman et al.'s conclusions, the cichlids are just one of many taxa reviewed by Yoder and Nowak, not only among vertebrates, but plants and invertebrates as well.  Many appear to have dispersed late enough that it stretches credibility to suggest that fossil calibration is a problem with so many of them dispersing (as opposed to a very early vicariance).  Especially the rodent and carnivore dispersal between 20 and 25 million years ago (see Ali and Huber, 2010;  Nature 463, 653-656; Mammalian biodiversity on Madagascar controlled by ocean currents).  The Ali and Huber paper solved the "problem" of ocean currents presumably going the wrong way for dispersal to occur, showing that the currents went the other way in the early-to-mid Tertiary.


                                          -------------------Ken Kinman                           Date: Sat, 22 Mar 2014 10:46:58 +1300

Subject: Re: [Taxacom] Madagascar's biota overwhelmingly from Cenozoic dispersers

From: m.j.heads at gmail.com

To: kinman at hotmail.com; taxacom at mailman.nhm.ku.edu



Hi Ken, Here is what I wrote (2012) about Yoder and Nowak's paper:    Yoder and Nowak (2006) gave a thorough

review of the molecular clock literature on Malagasy taxa. In every study of

plants the fossil-calibrated clocks dated the Madagascar clades as younger than

80 Ma and so they were all attributed to post-Gondwana dispersal, none to

vicariance. With a single exception, studies of animal taxa showed the same

result. All molecular dating studies of Malagasy invertebrates, reptiles and

mammals have concluded in favor of dispersal, as the inferred

(fossil-calibrated) divergence times were post-Mesozoic. The only sequenced

group in Yoder and Nowak’s review (2006) whose presence on Madagascar has been

attributed to vicariance is the fish family Cichlidae. Molecular dating studies

of this group avoided the use of fossil calibrations completely (Sparks, 2004,

Sparks and Smith, 2004; see Chapter 2). Instead, the vicariant distribution of

the two main molecular clades: Madagascar-Africa-South America, and

Madagascar-India-Sri Lanka, was correlated with tectonics – the opening of the

Mozambique Channel – and this was used as a calibration. (The same method is used

here for primates). So although Yoder and Nowak (2006: 416) concluded that the

importance of dispersal ‘cannot be denied’, really the only thing the cited

studies show is the importance of the calibration method.

Michael Heads





On Sat, Mar 22, 2014 at 7:49 AM, Ken Kinman <kinman at hotmail.com> wrote:



Has Vicariance or Dispersal Been the Predominant Biogeographic Force in Madagascar? Only Time Will TellAnnual Review of Ecology, Evolution, and SystematicsVol. 37: 405-431 DOI: 10.1146/annurev.ecolsys.37.091305.110239by Anne D. Yoder and Michael D. Nowak






Abstract.   Madagascar is one of the world's hottest biodiversity hot spots due to its diverse, endemic, and highly threatened biota. This biota shows a distinct signature of evolution in isolation, both in the high levels of diversity within lineages and in the imbalance of lineages that are represented. For example, chameleon diversity is the highest of any place on Earth, yet there are no salamanders. These biotic enigmas have inspired centuries of speculation relating to the mechanisms by which Madagascar's biota came to reside there. The two most probable causal factors are Gondwanan vicariance and/or Cenozoic dispersal. By reviewing a comprehensive sample of phylogenetic studies of Malagasy biota, we find that the predominant pattern is one of sister group relationships to African taxa. For those studies that include divergence time analysis, we find an overwhelming indication of Cenozoic origins for most Malagasy clades. We conclude that most of the present-day biota of Madagascar is comprised of the descendents of Cenozoic dispersers, predominantly with African origins.


















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