[Taxacom] Dispersal paradigm (was: Antarctic dispersal)

[John Grehan]

Ken,

I thought Mike was just citing the ducks as another example of a
Madagascar-NZ connection so I am not sure how you see it that he "fails to
mention that the "Madagascar-New Zealand-subantarctic island" duck clade is
only about 2.9 million years old (between a most likely minimum 1.78 mya
and most likely maximum 3.95 mya)." But one might ask you why you quote the
assertion that the duck clades is "only about 2.9 million years old
(between a most likely minimum 1.78 mya and most likely maximum 3.95 mya)"
when the divergence estimates are calibrated using fossils and so even the
'maximum 3.95 mya' is a minimum.

It may indeed be hard for you and other to "imagine stretching those dates
back far enough for a vicariance event" but that disbelief has no bearing
on how old the taxa are.

You say that the seeds of Euphorbia "probably" stuck to the bodies of a
flying bird. Can you back up that assertion of "probably"?

John Grehan


On Wed, Jun 18, 2014 at 1:28 PM, Ken Kinman <kinman at hotmail.com> wrote:

> Hi all,
>       I'm glad Michael brought up the paper by Mitchell et al., 2013.
>  What he fails to mention is that the "Madagascar-New Zealand-subantarctic
> island" duck clade is only about 2.9 million years old (between a most
> likely minimum 1.78 mya and most likely maximum 3.95 mya).   How one could
> imagine stretching those dates back far enough for a vicariance event just
> makes me shake my head in disbelief.
>        The ratite dispersal was no doubt earlier, but still during the
> Cenozoic.  As for how Euphorbia seeds got from New Zealand to Madagascar or
> vice versa (or even from Antarctica in both directions), they probably
> stuck to the bodies of ducks or flying ratite ancestors or some other kind
> of bird.  Anyway, I am now even more convinced that dispersal was a major
> factor in ratite evolution.
>  --------------------------Ken
>
> -------------------------------------------------------------------------------------------------------------------
> > Date: Wed, 18 Jun 2014 16:40:29 +1200
> > From: m.j.heads at gmail.com
> > To: deepreef at bishopmuseum.org; taxacom at mailman.nhm.ku.edu
> > Subject: Re: [Taxacom] Dispersal paradigm (was: Antarctic dispersal)
> >
> > Hi Richard,
> >
> > You mentioned vicariance and dispersal in groups other than birds and
> > plants. Birds are used a lot in biogeography because they're the best
> known
> > group, but different groups of algae, fungi, insects, fishes (marine,
> > freshwater and diadromous), etc. are discussed in my Australasia book as
> > they illustrate standard patterns.
> >
> > You suggested that 'there are very, very few generalities we can make
> > concerning broad patterns in the history of evolution of life on Earth'.
> > One generality seems to be that the same distributions are, surprisingly,
> > repeated in groups with completely different ecology and means of
> > dispersal.
> >
> > For example, Ken brought up the Madagascar - New Zealand connection in
> > ratites (elephant birds and kiwis). The same distribution also occurs in
> > the beetle family Chaetosomatidae, and a correspondent has just written
> to
> > me citing a clade of  ducks comprising four NZ species and A. bernieri in
> > Madagascar (Mitchell et al., 2013). In plants, Euphorbia glauca of NZ is
> > sister to E.  emirnensis of Madagascar (Riina et al., 2013). These groups
> > all have very different ecology and means of dispersal, suggesting that
> > these factors are not the cause of the pattern.
> >
> >
> >
> >
>
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