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

[Michael Heads]

Hi Ken,

You said about Yoder's study: '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'.

All the studies (except one) used one calibration method (fossils) and
inferred the same process (dispersal). The only other paper used a very
different calibration method (tectonics) and inferred a totally different
result (vicariance). The only obvious conclusion is that calibration is
crucial and that there are unresolved issues.

Looking at it in more detail, neither the reviewed papers nor the review
itself addressed the problem of the 'priors' used in dating analyses. In
other words, how much older than the oldest fossil can its clade be?

The Yoder work on Madagascar is discussed in more length elsewhere in my
2012 book. I also discussed the Ali and Huber work you mentioned: 'The Ali
and Huber paper solved the "problem" of ocean currents...'. I think you
should read my book! A&H explained how lemurs might have been stranded in
Madagascar by rafting, but this is only part of the Madagascar puzzle.
Strepsirrhines are in Africa and Madagascar (lemurs), but not
America, while haplorhines are in Africa and America, but not Madagascar.
This is a very symmetrical structure. If strepsirrhines could raft to
Madagascar, why did not haplorhines? And why could haplorrhines manage to
raft to America when they couldn't even get to Madagascar? A&H didn't
address these aspects. You can't just answer one part of the problem -
anyone can think up an ad hoc reason for one particular step. In addition,
haplorhines are more diverse in western Africa, strepsirrhines in east
Africa - you have to explain that in a way that fits with the rest of the
pattern.

Michael


On Tue, Mar 25, 2014 at 2:45 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<http://rspb.royalsocietypublishing.org/search?author1=Matt+Friedman&sortspec=date&submit=Submit>
> ,
> Benjamin P. Keck<http://rspb.royalsocietypublishing.org/search?author1=Benjamin+P.+Keck&sortspec=date&submit=Submit>, 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.
>
>
>
> ______________________________________________
>
>
>
>
>


-- 
Dunedin, New Zealand.

My recent books:

*Molecular panbiogeography of the tropics.* 2012. University of California
Press, Berkeley. www.ucpress.edu/book.php?isbn=9780520271968

*Biogeography of Australasia:  A molecular analysis*. 2014. Cambridge
University Press, Cambridge. www.cambridge.org/9781107041028