[Taxacom] Meliaceae (vicariance??)

[John Grehan]

Nicely summarized with precise details (vs my overly general description).
And I overlooked that remark about panbiogeographers ignoring dispersal -
which they do not of course and never have. Its one of those myths that
keeps popping up over the decades.

John Grehan

On Sat, Nov 16, 2019 at 6:18 PM Michael Heads via Taxacom <
taxacom at mailman.nhm.ku.edu> wrote:

> The mahogany family Meliaceae (700 spp.) and its sister Simaroubaceae (100
> spp.) form a pantropical clade that also occurs in some warmer temperate
> regions. The most striking anomalies in the distribution are two great
> areas of absence, one in a large region of the central Pacific (Hawaii,
> Cooks to Marquesas) and one in SW Australia. There are no known
> *ecological*
> factors that would exclude the clade from these regions, and introduced
> members of the clade are naturalised there. So what is the reason for the
> absences? An enquiry into possible *historical* factors soon comes up
> against three facts:
>
> 1. Meliaceae + Simaroubaceae are absent from the two regions, but the
> clade’s sister, the orange family Rutaceae, has notable centres of endemism
> and diversity in both.
>
> 2. The two regions are also well-known as centres of endemism for many taxa
> other than Rutaceae, and centres of endemism are invariably areas of
> anomalous absence in other groups.
>
> 3. Despite their allopatry in the two regions, Meliaceae + Simaroubaceae
> and Rutaceae *do* occur together through tropical America, Africa and Asia
> and on thousands of islands (in the West Indies, Indonesia, Melanesia, SW
> Pacific).
>
> Because of molecular clock dates, it is now common to ascribe allopatry not
> to vicariance but to priority effects – the first colonizers keep out new
> entrants by competitive exclusion. For example, as Ken suggests, dispersal,
> priority, and competitive exclusion might account for Rutaceae being on
> islands where Meliaceae + Simaroubaceae are absent. However, the theory
> does not account for the distributions of the two families as a whole,
> without bringing in further, ad hoc arguments.
>
> The facts can be accounted for by 1. Initial vicariance between the two
> clades; 2. Massive overlap through most of the tropics, with the initial
> allopatry preserved in just two regions.
>
> Ken wrote that: ‘There is already lots of published evidence that a
> considerable amount of dispersal occurred in this case. Panbiogeographers
> just dismiss all of it...'. This is incorrect; no-one is denying dispersal.
> For example, in my paper the geographic overlap of Meliaceae +
> Simaroubaceae and Rutaceae through most of the tropics is explained by
> early range expansion of one or both clades by normal dispersal using
> normal means.
>
>
> On Sat, Nov 16, 2019 at 8:02 AM Kenneth Kinman via Taxacom <
> taxacom at mailman.nhm.ku.edu> wrote:
>
> > Hi All,
> >            There is already lots of published evidence that a
> considerable
> > amount of dispersal occurred in this case.  Panbiogeographers just
> dismiss
> > all of it with the same old arguments about fossil calibration errors.
> If
> > they would only widen the taxonomic context (as I did in the
> > Lepidoptera-Trichoptera posts on November 4th), perhaps they would
> realize
> > that the evidence presented by dispersalists is good science (not to be
> > dismissed with the same old tired arguments).   Go beyond the
> > Meliaceae-Simaroubaceae-Rutaceae clade, and you are likely to see how
> > evidence from outgroup relatives fits better with dispersal than with
> > vicariance.
> >        Muellner-Riehl et al. (2016) proposed that Sapidales arose about
> > 112 million years ago, and that the two subfamilies of Meliaceae split as
> > early as 89.8 million years ago.  This fits in pretty well with the
> recent
> > 2018 (Atkinson, 2018) report of a stem-lineage fossil of Meliaceae dated
> at
> > 79 million years ago, and the stem-lineage could easily go back more than
> > 10 million years before that fossil.  But that still does not mean it
> goes
> > back far enough  that vicariance explains the biogeography of Family
> > Meliaceae.   Africa and South America separated much earlier (about 140
> > million years ago), and they had separated from East Gondwana about 180
> > million years ago.   Arguments seem unconvincing blaming an imagined poor
> > fossil record that far back.
> >        A center of origin in Africa of Family Meliaceae makes more sense
> > (about 85-90 million years ago), although an origin in Eurasia is also
> > possible.    It would then have expanded north into Europe and from there
> > into North America before they separated about 80 million years ago.
> > Therefore, with the stem-lineage fossil of Meliaceae (Atkinson, 2018) in
> > North America at 79 million years ago, one would expect that they had
> > spread from Africa into Europe about 80-85 million years ago.   The
> > eastward expansion through southern Asia could have begun about the same
> > time (but didn't reach Australia until much much later, so Rutaceae could
> > have claimed SW Australia first and competitive exclusion kept Meliaceae
> > out).   Competitive exclusion could also explain the absence of Meliaceae
> > in Hawaii.
> >                                  -----------Ken Kinman
> >
> > Muellner-Riehl et al. 2016
> > https://onlinelibrary.wiley.com/doi/abs/10.12705/655.5
> >
> > Atkinson, 2018:
> >
> >
> http://2018.botanyconference.org/engine/search/index.php?funcÞtail&aid27
> >
> > Koenen et al., 2015
> > https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.13490
> >
> >
> >
> >
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >
> >
> >
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>
>
> --
> Dunedin, New Zealand.
>
> My books:
>
> *Biogeography and evolution in New Zealand. *Taylor and Francis/CRC, Boca
> Raton FL. 2017.
>
> https://www.routledge.com/Biogeography-and-Evolution-in-New-Zealand/Heads/p/book/9781498751872
>
>
> *Biogeography of Australasia:  A molecular analysis*. Cambridge University
> Press, Cambridge. 2014. www.cambridge.org/9781107041028
>
>
> *Molecular panbiogeography of the tropics. *University of California Press,
> Berkeley. 2012. www.ucpress.edu/book.php?isbn—80520271968
>
>
> *Panbiogeography: Tracking the history of life*. Oxford University Press,
> New York. 1999. (With R. Craw and J. Grehan).
> http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC
> <
> http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC&dq=panbiogeography&source=gbs_navlinks_s
> >
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> Nurturing nuance while assaulting ambiguity for 32 some years, 1987-2019.
>