[Taxacom] Madagascar's biota overwhelmingly from Cenozoic dispersers

[Michael Heads]

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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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