[Taxacom] Panbiogeography

[Michael Heads]

Hi Jason,

I don't get the impression from the microbiologists that the new critique
of 'everything is everywhere' is just an attack on a strawman. It looks
much more like a genuine paradigm shift. E.g. have a look at the papers in
a recent volume: Fontaneto, D. (ed.) *Biogeography of Microscopic
Organisms: Is Everything Small Everywhere? *Cambridge University Press.
There's a real mood of excitement. After our last correspondence a
colleague sent Chapter 2, a very nice review by David Williams at the
British Museum titled 'Historical biogeography, microbial endemism and the
role of classification: everything is endemic'.



On Rhagoletis, Feder et al. (2003) wrote: ?we infer that an ancestral,
hawthorn-infesting *R. pomonella* population became geographically
subdivided into Mexican and North American isolates ?1.57 million years
ago. Episodes of gene flow from Mexico subsequently infused the North
American population'. Michel et al. (2007 Mol Ecol) suggested that
?volcanic activity in the eastern EVTM [Eje Volcanico Trans Mexicano] may
have been responsible for the initial geographical isolation of the Mexican
and northern hawthorn-fly populations'. This is a common pattern, with
allopatric differentiation, followed by subsequent overlap and local
ecological sorting.



I'm quite open to the idea of sympatric speciation - it would be a good
explanation of overlap - but it would tend to lead to sister species with
the same geographic distribution (and different ecology), and this is very
rare. In all the papers I've seen where proponents of sympatric speciation
actually map the clades (e.g. Dawson et al., 2012 Mol Ecol; Hodge et al,
2013 J Biogeogr), the descendants have very different distributions, with
local overlap. This doesn't look like sympatric speciation to me, but you
could explain it by allopatric differentiation and subsequent overlap.








On Mon, Apr 14, 2014 at 5:22 PM, JF Mate <aphodiinaemate at gmail.com> wrote:

> Hi Michael,
>
> sorry for the delay. Currently with friends and family so I am not
> keeping up. In regards to your question,  I work on Aphodiinae (all
> aspects)  and with Hydrophiloidea for faunistics.
>
> Regarding Rhagoletis, the papers from Feder et al suggest that the
> genes involved in diapause originated, probably, in allopatry and then
> spread into the more northern  R. pomonella populations. This does not
> exclude sympatric evolution. Instead, basic genetic "adaptive packs"
> originated in allopatry and spread into the US populations
> (introgression scenario) before human introduction of apples. These
> "packs" where selected in toto thanks to the polymorphic inversions,
> and their spread facilitated, it is assumed, due to the adaptive
> advantage to hawthorn feeding flies along the latitudinal temperature
> clines. Afterwards, these inversions would have preadapted R.
> pomonella for host switching and the sympatric formation of host
> races. So the papers provides a molecular mechanism to sympatry in the
> form of "preadaptations". As to the overlap, the SN and N populations
> are broadly sympatric and haw feeding and apple feeding flies exist
> side by side. It is quite clear in the paper.
>
> Now, my issue with the statement "everything is everywhere (and the
> environment selects)" is that it is a bit of a strawman, like blaming
> Darwin for dispersalism. Things have changed quite a bit since the
> Victorians. We even accept certain forms of quasi-lamarckian
> evolution!
>
> Best
>
> 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—80520271968

*Biogeography of Australasia:  A molecular analysis*. 2014. Cambridge
University Press, Cambridge. www.cambridge.org/9781107041028