[Taxacom] North America, Central America + S.E. Asia sister taxa

John Grehan jgrehan at sciencebuff.org
Tue Dec 20 12:03:59 CST 2011


Kip,

Thanks, that's understandable. Yes there are different patterns in
geographic detail with respect to east Asia and the New World, and yes
your group is a particular distribution in that respect. The term
'Trans-Pacific' does, of course apply to all such patterns regardless of
their differences in detail, but its not vague at all with respect to
identifying that massings as having proximity over the Pacific basin
rather than the Indian or Atlantic. That in turn identifies the Pacific
basin as having something more to do with the disjunction than the other
basins and the tectonics they represent.

When you say "different historical events" it is true at some level of
detail that for individually different distributions might have
differences in 'history' but that does not mean it is necessarily so. It
depends on what one means by 'history'. For example, the same historical
event involving the geological history of the Pacific basin may have
resulted in different trans-Pacific distributions because of differences
in the ancestral range of each group prior to that historical event or
process.

I'm not sure that occurrence east of the Rockies increases the
likelihood of a trans-Atlantic biogeography (is that what you mean by
'Laurasian'?) since many Pacific taxa are widespread in N America while
others are more western, others more eastern(Fagus is a good example for
the living representatives).

John Grehan  

-----Original Message-----
From: Kipling (Kip) Will [mailto:kipwill at berkeley.edu] 
Sent: Tuesday, December 20, 2011 11:56 AM
To: John Grehan
Cc: TAXACOM
Subject: Re: [Taxacom] North America, Central America + S.E. Asia sister
taxa

Johan,
Peculiar in the sense that it is atypical for ground beetle
distributions, thus my search to see if it found in other group. 
However, I would not describe it as "South East Asia and the New World",
since the New World is a much, much bigger area than the area where the
beetles are found, nor does "trans-Pacific" clearly capture the pattern.

The latter strikes me as vague since Australia-New Zealand-Chile and
Korea-California are both "trans-Pacific", but surely due to different
historical events, and these different from North America, Central
America-S.E. Asia.

To be more specific the New World clade is only found east of the
Rockies would be more likely have a Laurasian connection to the
Thailand-Vietnam clade, I think. We have plenty of Laurasian or
Beringial connections in ground beetles, but typically these have some
elements also in the Paleartic, which is lacking in my beetles. Perhaps
they had a much wider distribution once and extinction has eliminated
the middle. However, such a scenario feels a bit too Darlingtonian for
my me at this point.

Kip


On 12/20/2011 7:03 AM, John Grehan wrote:
> Kip,
>
> Thank you for the clarification. I guess I am puzzled about your 
> referring to it as a 'peculiar' distribution, at least with respect to

> a taxon existing in South East Asia and the New World since these 
> types are patterns are commonplace and are spatially diagnostic as 
> being trans-Pacific.
>
> Admittedly, many such groups may lack a rigorous phylogenetic 
> analysis, but on the other hand I suspect many do.
>
> John Grehan
>




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