[Taxacom] Plant Dispersal across the Atlantic (was: Biogeography of Meliaceae)

[John Grehan]

I would respectfully submit that this paper is just a comprehensive example
of nonsense science. It is all pure imagination.

John Grehan

On Wed, Oct 16, 2019 at 9:47 AM Kenneth Kinman via Taxacom <
taxacom at mailman.nhm.ku.edu> wrote:

> Hi All,
>        To put this into a much broader context, I would recommend reading
> a more comprehensive study (by Renner, 2004; "PLANT DISPERSAL ACROSS THE
> TROPICAL ATLANTIC BY WIND AND SEA CURRENTS").  It includes up to 110 genera
> of plants which are thought to exhibit Trans-Atlantic dispersals (during
> the Cenozoic) by water currents or wind currents (rather than by older
> vicariance events).   A weblink to Renner's paper is given below.
>                           -----------------------Ken Kinman
>
>
> http://citeseerx.ist.psu.edu/viewdoc/download?doi.1.1.516.6358&rep=rep1&type=pdf
>
>
>
> ________________________________
> From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of John
> Grehan via Taxacom <taxacom at mailman.nhm.ku.edu>
> Sent: Tuesday, October 15, 2019 10:50 AM
> To: taxacom <taxacom at mailman.nhm.ku.edu>
> Subject: [Taxacom] Biogeography of Meliaceae
>
> 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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