[Taxacom] Panbiogeography

[Michael Heads]

Hi Jason,

Another colleague sent a good paper on the 'everything is everywhere'
debate - it's:
O'Malley, M. A. (2007). The nineteenth century roots of'everything is
everywhere'. *Nature Reviews Microbiology*, *5*(8), 647-651. 'The
identification of geographical patterns in microbial distributions has
begun to challenge purely ecological explanations of biogeography and the
underlying principle of 'everything is everywhere: but the environment
selects'.' It's a good review. Of course, no-one is suggesting that
dispersal does not occur, but chance dispersal/ecology does not seem to be
the explanation for these patterns.

You wrote: In regards to the range overlap of sister species, sympatric
speciation doesn?t have to result in broad sympatry. In fact it probably
will lead to the opposite result due to local adaptation'. But imagine a
species found in an area  of hilly rainforest say 50 km across that
differentiates by ecological adaption into a ridge species and a
gully species. Wouldn't you expect them to have more or less the same
geographic distribution?

Michael


On Sat, Apr 19, 2014 at 2:34 AM, JF Mate <aphodiinaemate at gmail.com> wrote:

> Apologies to Taxacomers for this ongoing thread.
>
> Dear Michael, out of curiosity I have checked the book (or what was
> available to me) and I will point out the following quotes:
> p248-249:  "To summarise, in spite of the unsatisfactory knowledge of
> their taxonomy, Gastrotricha do exhibit specific
> patterns of diversity and distribution. Notwithstanding possible
> problems and biases in the interpretations of
> gastrotrich distribution, some blueprints emerge: the percentage of
> widespread taxa is high, especially among the highly
> speciose chaetonotids; some species have a more restricted geographic
> range, but even these species are relatively
> widespread within one biogeographic region."
> p252: " Notwithstanding possible problems and biases in the
> interpretations of rotifer distribution, one pattern is
> clear: the percentage of widespread taxa is high; some species are
> more restricted geographically, but even the species
> with more restricted distributions are relatively widespread within
> one biogeographic region. Moreover, almost all genera
> and higher taxa are really cosmopolitan, one feature that is
> completely different from macroscopic organisms, even if
> the defi nition of taxa higher than species in diff erent groups may
> not be directly comparable."
> p254: "The confusion over group-complexes and potential errors in
> published taxonomic records would imply that the phylum
> Tardigrada was not a good subject for biogeographic studies. However,
> there seems to be a general understanding that
> while there are cosmopolitan genera, most of these exhibiting
> parthenogenesis and capable of cryptobiosis (Pilato, 1 979),
> not all genera are cosmopolitan and many of these have a lower
> capacity for cryptobiosis and/ or reproduce sexually (Kristensen,
> 1987 )
>
> Some things stay put, many are very widespread. Still, the number of
> "widespread" microbial species is north of 20-30% which is
> unheard of in pretty much any other group that I can think of. As to
> the "strawman", if you read carefully other publications by the
> editor you can see that the "paradigm" he is challenging is really
> this, a paper by Finlay, B.J. (2002: Global dispersal of free-living
> microbial eukaryote species. Science 296, 1061-1063). It is behind a
> paywall so I can?t acess it right now. But from the
> abstract (plus other later papers Finalya and collaorators) I can
> conclude that in their research they find Protozoa to be "widespread"
> and that they are essentially different to bigger organisms. So out
> comes the "forgotten phyla brigade" to say, not so fast.
> Everybody needs a target to stick their own research but this
> paragraph from a separate paper (Fontaneto, D. & Hortal, J. (2012).
> Microbial biogeography: is everything small
> everywhere? In Microbial Ecological Theory: from Individuals to
> Ecosystems (ed. by L.A. Ogilvie and P.R. Hirsch)) puts everything in
> perspective: "Only recently, microbial biogeography has gained renewed
> vigour because of the resurgence of the
> ?Everything-is-Everywhere? hypothesis (Finlay, 2002; Fenchel & Finlay
> 2003; Finlay  & Esteban, 2007; see O?Malley, 2008 and Williams, 2011
> for historical reviews of
> this idea). We will not deal with the discussion on whether it is a
> true hypothesis in strict terms, as ?regardless of detail or
> explanation, the phrase ?everything is
> everywhere? is clearly false, and in any case, one would need to know
> in what sense the words ?everything? and ?everywhere? are intended. As
> soon as something is not
> found everywhere then everything (obviously) is not everywhere. This
> much could be easily agreed upon? (quotation from Williams, 2011)."
> So Fontanto et al agree that the statement is at best a catchy
> sound-bite, so why use it at all I wonder? Hardly a paradigm shift. So
> how does this throw a spanner into dispersal exactly?
>
> As for sympatric speciation:
>
> "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."
>
> Feder et al are clear that it is introgression and not lineage
> sorting. Further, they provide a mtDNA tree so you can see that it is
> not
> Mexican flies moving into apples (i.e. there is only one
> metapopulation in the US and not two cryptic, sympatric populations)
> but Northern
> flies which had some genes from a different population.
> But once infused into the Northern population it was sorted and
> selected along a latitudinal cline and they were an exaption (probably
> amongst
> others, as the authors concede) that allowed R. pomonella to exploit
> apples when introduced much later.
> The actual speciation only started afterwards as a consequence of the
> different fruiting times, assortative mating, etc. All sympatric
> processes.
>
> In regards to the range overlap of sister species, sympatric
> speciation doesn?t have to result in broad sympatry. In fact it
> probably will lead to the opposite
> result due to local adaptation. Focusing on the R. pomonella complex,
> host races? ranges will be contained within that of their host and not
> of the original R. pomonella population.
> Furthermore, chromosomal inversions, although they do not preclude
> mating they can facilitate local adaptation (reduced recombination)
> and in
> the process kickstart speciation (genetic isolation). For a recent
> example check Lowry D. B, Willis J. H (2010) A widespread chromosomal
> inversion polymorphism contributes to a major
> life-history transition, local adaptation, and reproductive isolation.
>
> 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—80520271968

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