[Taxacom] Panbiogeography

[Michael Heads]

Hi Jason,

You say: "I´m surprised that you, of all people, use the numbers game to
bolster your
position. Nevertheless, and in spite of the 412 papers quoting "Everything
is everywhere"...".

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.

"What I can say is that panbiogeography, through its outright
rejection of dispersal...",

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.

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).

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.


On Thu, May 1, 2014 at 6:44 PM, JF Mate <aphodiinaemate at gmail.com> wrote:

> Dear Michael
>
> I´m surprised that you, of all people, use the numbers game to bolster your
> position. Nevertheless, and in spite of the 412 papers quoting "Everything
> is everywhere", smaller organisms, or at least their genes, appear to be
> better at dispersing (30%+ very widespread according to your own sources),
> than bigger organisms, a not unexpected result. I have even provided the
> example of an arthropod (D. pullex) that is so widespread throughout the
> globe it barely has genetic structure throughout the N. hemisphere. So what
> are you arguing exactly? That vicariance is more important? I can´t argue
> with that. What I can say is that panbiogeography, through its outright
> rejection of dispersal, has less explanatory power than other approaches.
>
> The reference by Rossberg etal (2013) is just to prove a simple point, that
> we don´t know what exactly we are dealing with when we talk about
> "microorganisms". We may have reticulation to such a degree that the idea
> of "species" may be meaningless (for example of E. coli strains).
>
> On sympatric speciation. Allopatry´s effects are community-wide, whereas
> sympatry will occur in particular lineages when conditions conducive to
> speciation (whatever they may be) are met . By definition it will be rare,
> so this in itself is not evidence against it´s existence. We may assume
> that most lineages will speciate no-sympatrically and only rarely will a
> species-pair speciate via sympatry. Barraclough and Vogler´s method doesn´t
> (can´t) account for this. So mapping is not going to help you very much.
> Furthermore, as shown in the R. pomonella complex, if the genes involved in
> speciation form a gradient (i.e. they are an exaption that determines their
> geographical distribution) then the expectation of range overlap cannot be
> met.
>
> Bolnick and Fitzpatrick´s (2007) review of sympatry provides a large number
> of examples with varying support for sympatry. There are certainly gaps in
> the knowledge so some may prove to be nonsympatric speciation, and Howea
> may be such a case (however see reply to Tuessy (2006) by Savolainen et al
> (2006) which answers your concerns). That still leaves a lot of other
> cases, including R. pomonella, which strongly indicate sympatric
> speciation.
>
> Finally, regarding your comments on Peccoud et al. They are not making any
> phylogeographic claims. Instead they are looking at the genetic structure
> of a single species, the pea aphid, in a small area (40Km). They identify
> 11 clades which correspond to host races, with hybridisation ranging from
> 0% in 3 lineages to 9% in two others. The low hybridisation is due to
> assortative mating (mating happens on the host plant, like in R. pomonella)
> and lower fitness of hybrids or of races switching hosts.
>
> Other studies looking at phylogeography in this species using mtDNA have
> found very little variation, suggesting a very recent origin for these
> races. A later paper by Peccoud et al (2009 PNAS) suggests a radiation
> burst 9,5-3,000 years ago for the sampled host races (sequencing the
> symbiont Buchnera sp). All this suggests that the initial diversification
> and the ongoing reinforcement has happened in sympatry.
>
> Best
>
>
> Jason
>
> >
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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