[Taxacom] Biogeography of Meliaceae

[Michael Heads]

Dear Colleagues,

Here's a link to the high resolution version of my paper in the Mabberley
Festschrift volume:
https://drive.google.com/open?idFUJKtBnZtof_RGdjalazhXBW1enYR8P

On Wed, Oct 16, 2019 at 4:51 AM John Grehan via Taxacom <
taxacom at mailman.nhm.ku.edu> wrote:

> Heads, M 2019. Biogeography and ecology in a pantropical family, the
> Meliaceae. Gardens’ Bulletin Singapore 71(Suppl. 2):335-461.
>
> A copy of this paper can be obtained via the author. It provides a
> comprehensive approach to the biogeography of a widespread taxon. Also
> included is a critique of fossil based molecular dating (excerpts below).
> Any counter points posted to Taxacom would be of interest, but please read
> the paper first. Note Bromham's (2019) characterization of molecular
> dating. It seems that more researchers are starting to catch on to the
> absurdity of magically transmogrifying minimums into maximums.
>
> John Grehan
>
> ABSTRACT. This paper reviews the biogeography and ecology of the family
> Meliaceae and
> maps many of the clades. Recently published molecular phylogenies are used
> as a framework
> to interpret distributional and ecological data. The sections on
> distribution concentrate
> on allopatry, on areas of overlap among clades, and on centres of
> diversity. The sections
> on ecology focus on populations of the family that are not in typical,
> dry-ground, lowland
> rain forest, for example, in and around mangrove forest, in peat swamp and
> other kinds of
> freshwater swamp forest, on limestone, and in open vegetation such as
> savanna woodland.
> Information on the altitudinal range of the genera is presented, and brief
> notes on architecture
> are also given. The paper considers the relationship between the
> distribution and ecology of
> the taxa, and the interpretation of the fossil record of the family, along
> with its significance for
> biogeographic studies. Finally, the paper discusses whether the evolution
> of Meliaceae can be
> attributed to ‘radiations’ from restricted centres of origin into new
> morphological, geographical
> and ecological space, or whether it is better explained by phases of
> vicariance in widespread
> ancestors, alternating with phases of range expansion.
>
> Excerpts
>
> Bromham (2019) suggested that molecular clock dating “requires us to
> believe six impossible things before breakfast�. Many of the assumptions
> “are based
> on statistical tractability rather than being informed by improved
> understanding of
> molecular evolution, yet changing the assumptions can influence molecular
> dates.
> … If our assumptions are wrong, then our inference could be misleading,
> however
> much data we have…. All molecular dating analyses require us to make
> statements
> of belief, irrespective of whether we call them models, assumptions, or
> priors. We
> need to recognise that while some disagreements between molecular dates are
> due
> to differences in data or method, many are due to different beliefs
> codified in the
> analyses…�.
> To summarise, a fossil gives a minimum age for its clade, and we do not
> know
> how much older than this date the actual clade age is. Biogeographic
> calibrations
> suggest that many clades are much older than their oldest fossil (Heads,
> 2014).
>
>
> Koenen et al. (2015) ran three analyses with different maximum age priors,
> as
> follows: 1. Using a fossil-calibrated crown age for Sapindales (c. 71 Ma)
> as a hard
> maximum bound; 2. Using a fossil-calibrated stem age of Sapindales (98 Ma)
> as a
> hard maximum bound; 3. Using the age of the first tricolpate pollen (127
> Ma) as a hard
> maximum bound for the age of eudicots.
>
> The authors regarded the third method as most likely. Nevertheless, the
> authors
> found that in scenarios 2 and 3, the crown age of the Sapindales becomes
> ‘unrealistically
> old’, especially when the tricolpate pollen age is used. (Using tricolpate
> pollen, the
> authors calculated that Sapindales originated at 120 Ma and Meliaceae at 80
> Ma, but
> biogeography indicates that this last date is still much too young).
> By stipulating such narrow priors and thus calculating such young clade
> ages,
> the authors were able to support traditional chance dispersal over
> vicariance: “…
> Old World/New World disjunctions are indeed substantially too young
> (Oligocene
> or younger) for vicariant explanations… [Thus] Our results indicate
> [Oligocene or
> younger] trans-Atlantic dispersal from Africa to the New World…� (Koenen et
> al.,
> 2015). Again, this simply reflects the very narrow priors that were
> imposed. The time
> and place of origin of Meliaceae can be regarded as open questions.
>
> Twenty years ago, most authors argued that species had their origin in the
> Pleistocene (since 2.6 Ma). The argument that species could ever be
> Cretaceous
> (before 65 Ma), made on the basis of treating fossils as minimum clade ages
> and on
> biogeography (Craw et al., 1999), was controversial. Now, most authors
> accept that
> species may be as old as Miocene (5–20 Ma). However, recent molecular
> studies have
> proposed that species of plants, such as Gunnera herteri Osten (Bacon et
> al., 2018),
> and animals, such as petalurid dragonfly species and the frog Leiopelma
> hochstetteri
> (Ware et al., 2014; Carr et al., 2015), date back to the Cretaceous (65
> Ma).
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> Nurturing nuance while assaulting ambiguity for 32 some years, 1987-2019.
>


-- 
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>