[Taxacom] Antarctic dispersal (was: Another blow to vicariance in ratite evolution

[Michael Heads]

Hi Ken,

The Indian Ocean clade of Crossosomatales (Madagascar - New Zealand and
vicinity) has its sister group neatly allopatric to its north (New Guinea,
Sri Lanka etc. northwards), so the simplest explanation is that they both
originated by vicariance. The break between the two (located between
Madagascar and Sri Lanka, between New Caledonia and New Guinea, etc.)
coincides with belts of major rifting as well as breaks in countless other
groups.

The 80 m.y. date for the clades is fossil calibrated and so it is a mimimum
age. This is useful as it rules out earlier events (not older ones) as
possible causes.

For the ratite clade, you seem to be supporting the idea that everything
was everywhere and then gradually the distributions formed by extinction.
So how and why were they everywhere to start with? It just gets more and
more complicated for a very simple case of allopatry.


On Mon, Jun 9, 2014 at 2:55 PM, Ken Kinman <kinman at hotmail.com> wrote:

> Hi Mike,
>         The Crossosomatales southern clade is probably only about 80
> million years old, so dispersal to Madagascar seems to be a good bet (and I
> believe it also dispersed to the Seychelles and Mascarene islands as well).
>  This clade probably existed in Antarctica and Australia (fossil pollen
> records), so the current distribution is no doubt a combination of early
> vicariance, later dispersals, and then extinction in intervening areas
> (including Antarctica and Australia).  I don't know much about the beetle
> family Chaetosomatidae, but perhaps Stephen Thorpe might have an opinion on
> that.
>
>          In any case, since only that beetle family has the same
> distribution as the elephant bird-kiwi clade, I would certainly not call
> that much of a pattern!!!  And the elephant bird-kiwi clade is probably
> even younger than 80 million years old, so dispersal of a flighted ancestor
> (of kiwi and elephant birds) from Antarctica in the early Cenozoic seems a
> very probable hypothesis, and again followed by extinction of the clade in
> Australia (due to competition with other ratites) as well as extinction in
> mainland Africa (due to competition with early ostriches).
>
>         So if there is a pattern to be seen in such cases, I would suggest
> that Antarctica is going to be a major factor, and that the massive
> extinction of the biota in Antarctica during the early-to-mid Cenozoic (and
> paucity of a known fossil record there) makes vicariance more appealing
> than it actually is for many taxa.  In particular, the multiple losses of
> flight among ratite taxa makes perfect sense to me.  Why John calls such
> suggestions ignorant (much less stupid) baffles me.
>                          ----------------------------Ken Kinman
>
>
> ------------------------------
> Date: Mon, 9 Jun 2014 11:12:39 +1200
> Subject: Re: [Taxacom] Another blow to vicariance in ratite evolution
> From: m.j.heads at gmail.com
> To: kinman at hotmail.com; taxacom at mailman.nhm.ku.edu
>
> Hi Ken,
>
> On p. 74 of my 2014 book I cited the beetle family Chaetosomatidae, known
> only from Madagascar (Malgassochaetus) and New Zealand (Chaetosoma,
> Chaetosomodes). A similar pattern in plants occurs in the southern
> hemisphere clade of Crossosomatales; it's in Madagascar (also the adjacent
> coast of Africa and Cape Town) (Aphloia, Geissoloma) , New Zealand (Ixerba)
> and New Caledonia (Strasburgeria). (Both examples are cited, with
> references, in my 2014 book, p. 74).
>
>
> On Mon, Jun 9, 2014 at 10:42 AM, Ken Kinman <kinman at hotmail.com> wrote:
>
> John,       I would be interested in examples of those taxa with a
> Madagascar-New Zealand relationship.                                -----Ken
> John wrote:
>  There are other taxa with a Madagascar (and or S Africa) - New Zealand
> relationships and they are perfectly concordant with geologically mediated
> origins. Perhaps instead of stupid I should just say ignorant.
>
>
>
>
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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
>



-- 
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