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

[John Grehan]

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:

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> 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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