[Taxacom] Panbiogeography

[Michael Heads]

Hi Jason,

You say: 'There is nothing naughty in asking for testable definitions'.

A definition is the meaning of a *term *(not a thing) and is not
testable (apart from reference to common usage) - it's just a convention. A
metre is the distance light travels in 1/299 792 458 of a second. A tree is
a woody plant with a single trunk having a diameter of more than 10 cm or
whatever.

'Your definition of dispersal (as I understand it) is fundamentally
at odds with experimental evidence'.

Which evidence?

'When pressed you mention the
movement of plants from one corner of the garden to the other
or by alpine plants which disperse a meter here or there. This is why I take
issue with this definition that you and John spouse'.

The cases you mention are just examples, cited because they can actually be
observed, not just inferred. Other examples include seabirds that can be
seen flying 10 000 km across the Pacific.

'You don´t reject it outright, but you seek to trivialize it by pointing at
examples
that support this idea'.

I don't reject dispersal *at all.* My books are full of examples at
many different scales. I do not trivialize it, I make it quite clear that I
see it as a fundamental process. All clades overlap with many other clades,
and so unless you accept symatric evolution explains these, you must accept
huge amounts of dispersal.

'Anybody can cherry pick in this way. It is
like saying that dispersal can be all the way to the moon
simply because Deinococcus radiodurans hitched a ride on a satellite'.

Citing examples to illustrate a concept requires cherry picking by
definition.

'Or humans for that matter. There are numerous examples
of long range dipersal that happen frequently. There are also taxa
which cannot cross a road or a river or a forest clearing. Dispersal
is a range that is much greater than you want to consider'.

The best way to know what I do and don't consider is to read my books. I
accept dispersal at all scales, from global to local. For example, I cite
seabirds. If you sail across the Pacific for example, you will
see magnificent albatrosses days of sailing away from any land. It's very
impressive. They fly for many thousands of kilometres. And yet their
breeding ranges are very precise.

For example, Diomedea sanfordi at Dunedin and Chatham Islands, its sister
D. epomophora at Auckland and Campbell Islands. This could be the result
of a freak event of a single pregnant female flying just 500 km from
Auckland I. to Dunedin, and this has only ever happened once. This doesn't
seem very likely. OR it could be explained by the rifting open of the Great
South Basin, and the natal philopatry of the birds. In this model, no 'long
distance jump dispersal' (i.e. with speciation) is required, but this does
not deny that the birds continually disperse over many thousands of
kilometres.

On the other hand, the albatross family Diomedeidae overlaps thrioughout
its vast southern hemisphere-north Pacific range with its sister group,
Procellariidae + Hydrobatidae, and so massive amounts of range expansion -
 by normal means of dispersal - must be inferred in one or both
groups (unless you think the overlap is the result of sympatric
speciation).

For other seabirds, see the mainly allopatric breeding ranges of the 15
Pterodroma species in the Pacific, which divide up the ocean basin in a
very interesting way (Fig. 8-10 in my 2012 book). One of the two large
clades is mainly in the east, and the other is mainly in the west, and so
the pattern is unlikely to be the result of ecological factors. There is
minor overlap among the species, indicating range expansion by dispersal.

On sympatric evolution: you overlooked my comment about the Savolainen
result being based entirely on a flawed calibration. The differentiation of
the two species did not occur on the modern Lord Howe Island or anything
like it.

John said: "Or they are old races that have not differentiated much." You
replied: 'You would have to provide a mechanism that can stop random
genetic mutations from accumulating in both the aphid lineages and the
symbiotic microorganisms. Wishing for this is not enough'.

You don't have to stop mutation, just slow it down. How fast is the
mutation rate in these organisms? The rate is calculated based on
a calibration, among other things, which is why calibration is so important.


On Mon, May 5, 2014 at 12:44 AM, JF Mate <aphodiinaemate at gmail.com> wrote:

> Dear Michael and John,
>
> sorry if you received a half-baked draft. I let my son play with the
> phone and he did what kids do. So if it left you scratching your head,
> now you know why.
>
> "You've misunderstood my position - my work is based on the law of
> large numbers. I'm not interested in one-off phenomena,
> but in patterns that are repeated many times.
> You seemed to think that the 'everything is everywhere' topic was not
> a major issue, that's why I looked up the large
> number of recent papers that deal with it."
>
> I don´t understand your answer in the context of, say, <1mm organisms.
> If widespread dispersal is a double digit phenomenon, isn´t this
> relevant to consider? As Pierre said, if Panbiogeography accepted
> dispersal as most people understand it, they would just be a flavour
> of vicariance biogeography. As for "everything is everywhere". If you
> can produce a paper that supports this from 1950-1970 I will concede
> that this was the accepted dogma.
>
>
> "Why do you keep saying that I reject dispersal when I've already told
> you that my books propose large numbers of examples?
> I use dispersal - rather than sympatric speciation - to explain
> overlap, and because so many groups overlap,
> I regard dispersal as very important." ... (John) "Just saying so does
> not make it true. I think this is a bit naughty."
>
> There is nothing naughty in asking for testable definitions. Your
> definition of dispersal (as I understand it) is fundamentally
> at odds with experimental evidence. When pressed you mention the
> movement of plants from one corner of the garden to the other
> or by alpine plants which disperse a meter here or there. This is why I
> take
> issue with this definition that you and John spouse. You don´t reject
> it outright, but you seek to trivialize it by pointing at examples
> that support this idea. Anybody can cherry pick in this way. It is
> like saying that dispersal can be all the way to the moon
> simply because Deinococcus radiodurans hitched a ride on a satellite.
> Or humans for that matter. There are numerous examples
> of long range dipersal that happen frequently. There are also taxa
> which cannot cross a road or a river or a forest clearing. Dispersal
> is a range that is much greater than you want to consider.
>
> "For many dispersalist approaches the explanatory power generates
> acknowledged mysteries, puzzles, anomalies etc.
> This is greater explanatory power? "
>
> I call it reality, but to each their own.
>
> "On the Lord Howe island palms, you say "see reply to Tuessy (2006) by
> Savolainen et al (2006) which answers your concerns".
> Stuessy's points are important and the reply by Savolainen et al. is
> very weak. It depends entirely on their clock date for
> the 'sympatric' speciation event, and this was calibrated by assuming
> that Mascarenes endemics could be no older than their
> island! (See my critique of this naive approach in Syst Biol 60: 204.
> 2011)."
>
> Amongst the points mentioned by Savolainen et al, they pointed out
> that island lacked the structural
> complexity to account for physical barriers of any sort. Allopatry
> also requires a smoking gun you see, like vicariance it cannot be
> assumed.
> If you can provide actual evidence of a barrier that could have
> divided the ancestral island population then you have a case.
> Otherwise
> sympatry can be assumed, at least for now.
>
> "You say Peccoud et al. "are not making any phylogeographic claims".
> They map localities (geography) onto a phylogeny
> and use that to make deductions about 'sympatric speciation' (one of
> their keywords). That's phylogeography. "
>
> If they used samples from another locality they have to indicate so in
> the phylogram. That is just proper way to go about it.
> The indication on sympatric evolution comes not just from the evidence
> of a range of hybridisation rates discovered in the paper
> and the monophyly of the host races, but from the the lack of mtDNA
> variability which indicates very recent origin for the lineages and
> no allopatric mechanism to account for it.
>
> "Or they are old races that have not differentiated much."
>
> You would have to provide a mechanism that can stop random genetic
> mutations from accumulating in both the aphid lineages and the
> symbiotic
> microorganisms. Wishing for this is not enough.
>
> Jason
>
> _______________________________________________
> Taxacom Mailing List
> Taxacom at mailman.nhm.ku.edu
> http://mailman.nhm.ku.edu/mailman/listinfo/taxacom
> The Taxacom Archive back to 1992 may be searched at:
> http://taxacom.markmail.org
>
> Celebrating 27 years of Taxacom in 2014.
>



-- 
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