Taxacom: supposed evidence of Pacific ignuana dispersal
Michael Heads
m.j.heads at gmail.com
Sun Mar 23 17:27:48 CDT 2025
2025
it's nothing to do with wording. They don't mention the standard vicariance
model for iguanas-agamids. They don't seem to be aware of it, but maybe
they are.
On Mon, Mar 24, 2025 at 10:36?AM Geoff Read via Taxacom <
taxacom at lists.ku.edu> wrote:
>
> One more try at those ignus.
> John Grehan wrote:
> "That the Fiji iguana are most closely related to iguanas in America has
> never been at issue."
> Thanks John. However, that's what the paper is about. Really, of course you
> are free to criticise, but I don't think these authors deserve your scorn.
> They present their data, they discuss it thoroughly, and they include as
> possible explanations similar scenarios to those you believe in even if
> they don't use the specialist wording you would use. It's a molecular
> paper. Let's assess it on that basis. Future papers with further molecular
> data from a wider array of species might confirm their conclusions or might
> have a different interpretation. This is the usual progression, as we know.
> We shall see.
> Cheers,Geoff
> --
> Geoffrey B. Read, Ph.D.
> Wellington, NEW ZEALAND
> gread at actrix.gen.nz
>
> ---- Original Message ----
> From: John Grehan
> To: "Michael Heads"
> Cc: "Geoff Read" , "taxacom"
> Sent: Sun, Mar 23, 2025, 4:39 AM
> Subject: Re: Taxacom: supposed evidence of Pacific ignuana dispersal
> Geoff,
> Interesting to see your feedback. You conclude that the PNAS
> article and
> does ?seem? [what does ?seem? mean?] to be a very thorough
> even-handed assessment of all the possibilities in their discussion. I
> agree fully if ?thorough? and ?even handed? means that its
> even-handed to misrepresent fossil calibrated ages as actual or approximate
> rather than minimums, to represent their six areas as having some kind of
> empirical existence rather than fabrications (from where one knows not),
> and to be thorough it to ignore (or worse be ignorant of) a competing
> biogeographic hypothesis (The Pacific tectonic model). Yep ? if all those
> practices are ?thorough? and ?even-handed? then it?s certainly
> that.
>
> Regarding your reference to humans having observed iguanas making
> landfall
> on islands. That demonstrates nothing at all about allopatric divergence.
> All it shows is ecological dispersal effecting range expansion of a species
> range. No different to some bug being blown onto my vege garden (to my
> detriment)
>
> So, when you say that ?they seem to cover every prior hypothesis?.
> Well, they don?t and that?s a fact.
>
> Not sure what you mean when you say ?Don't go way up the
> classification.
> Do that and anything is a possibility.? Not really. The point is that
> the iguanas and their sister group is allopatric other than Madagascar. If
> one wants to invent all sorts of wanderings, how is it that over all this
> time these taxa are so allopatric, and as Heads notes, why do details of
> Old World distribution match standard biogeographic breaks? Vicariance
> origin would give a coherent explanation that allows for subsequent range
> expansion of either or both groups in what is now Madagascar.
>
> That the Fiji iguana are most closely related to iguanas in
> America has
> never been at issue. Not sure the context of your comment.
>
> Altogether a great paper if one is into sensationalist
> fabrications that
> leave out completing research findings. All very much the order of the day
> in many biogeographic works
>
> One of the popularist outlets included ?expert reaction? commentary
> ? from a dispersalist of course. I suggested they include my ?expert?
> reaction as well. This went to the Australia contact and they kicked the
> can to their NZ office. Perhaps I am a cynic, but I am guessing I won?t
> be surprised at the outcome (knowing what a closed shop the NZ
> institutional biogeography situation is).
> Cheers, John
> On Sat, Mar 22, 2025 at 6:26?AM Michael Heads via Taxacom wrote:
> If protoiguanid-agamids, and then pre- and proto-iguanids were already in
> the west Pacific, there is no need for fully-fledged iguanids, let alone
> Brachylophus, to migrate anywhere. The allopatry within Iguania
> (pleurodonts - Fiji and east, vs acrodonts - Solomons and west) is the key
> to the family distribution boundaries there (i.e.
> phylogenetic-biogeographic breaks), but the authors don't mention it.
> On Sat, Mar 22, 2025 at 9:45?PM Geoff Read via Taxacom
> wrote:
> >
> > No Michael, they don't "just say" that. There is extensive discussion
> > including of a Eurasian etc origin and they seem to cover every prior
> > hypothesis.Don't go way up the classification. Do that and anything is
> a
> > possibility.Down at the subfamily level of Iguaninae their work links
> > Fijian species Brachylophus bulabula in a clade with Dipsosaurus
> dorsalis
> > of the Southwestern United States and northwestern Mexico. And the other
> > iguanas nearby in their tree are N. American, Galapagos, and
> Antilles.The
> > tree as published is the salient part, not the full tree, which would be
> > nice to see - apparently that is in the supplementary data.
> > Geoff
> >
> > --
> > Geoffrey B. Read, Ph.D.
> > Wellington, NEW ZEALAND
> > gread at actrix.gen.nz (mailto:gread at actrix.gen.nz)
> >
> > ---- Original Message ----
> > From: Michael Heads
> > To: "Geoff Read"
> > Cc: "taxacom"
> > Sent: Sat, Mar 22, 2025, 5:27 PM
> > Subject: Re: Taxacom: supposed evidence of Pacific ignuana dispersal
> >
> > They just say: 'Pleurodonta = Iguanidae sensu ( 16 ) (e.g., anoles,
> > horned lizards, and relatives), are also largely restricted to the
> western
> > hemisphere'. They don't mention the sister group, let alone vicariance
> > with it, although it's a classic case of vicariance that's been cited
> many
> > times.
> > Pleurodonta: Madagascar + Americas + Fiji/Tonga. (i..e
> trans-Pacific
> > + Atlantic).
> > Acrodonta (sis group of Pleurodonta): Madagascar + Africa + Europe
> +
> > Asia to Australia and Solomons. (Trans-Indian).
> > The groups are allopatric except in Madagascar. The distributions are
> > determined by breaks (of a global ancestor) in the Atlantic, around
> > Madagascar, and between the Solomons and Fiji, all areas of major
> rifting.
> > There is no dispersal indicated except (perhaps) in Madagascar.
> > On Sat, Mar 22, 2025 at 12:26?PM Geoff Read via Taxacom wrote:
> > Here's one of the news articles mentioned by John.
> >
> >
>
> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fapnews.com%2Farticle%2Figuana-fiji-raft-float-journey-travel-9732d828c28a8374a6873fbc1b3d4af2&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574141058%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=ctVnK1IQlzA2scLaBtsNwf%2FQMCMi53CdU%2BEItrd7Kwg%3D&reserved=0
> (
> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fapnews.com%2Farticle%2Figuana-fiji-raft-float-journey-travel-9732d828c28a8374a6873fbc1b3d4af2&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574169475%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=DJXJipM%2F5p6SsBz%2FTWqixO%2BsFxheZODkaig7n9LuFmc%3D&reserved=0
> )
> > (
> >
>
> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fapnews.com%2Farticle%2Figuana-fiji-raft-float-journey-travel-9732d828c28a8374a6873fbc1b3d4af2&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574184071%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=cs3YcS1CJUMCngEXHBGhj%2FtY5gKj31MP5rZMmMgANis%3D&reserved=0
> (
> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fapnews.com%2Farticle%2Figuana-fiji-raft-float-journey-travel-9732d828c28a8374a6873fbc1b3d4af2&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574198064%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=4WKl5TOcHP%2F6beJxif8H00FQyP26HKhUF9aGgAwgPsc%3D&reserved=0
> )
> > )
> > I've read the PNAS article and it does seem to be a very thorough
> > even-handed assessment of all the possibilities in their discussion.
> > They say humans have observed iguanas making landfall on islands and
> quote
> > this presumably famous instance:
> > "In 1995, a vegetation mat
> > with at least 15 individual green iguanas (Iguana iguana) that likely
> > originated on the islands of Guadeloupe was observed making landfall
> > on Anguilla, an island 300 km away that was already inhabited by
> > a different species of iguana, I. delicatissima"
> > One quibble is that they work at a genus-level with little mention of
> > species. The genus is an 'it' as though it is a physical entity. A
> > practice more familiar of palaeontologists rather than molecular
> > biologists.
> > This quote illustrates the style: "Brachylophus , which contains 4
> extant
> > and 1 extinct species, is morphologically divergent from other iguanas
> and
> > occurs extremely far from all of its extant relatives"
> > Substitute 'are' for 'is' and 'their' for 'its' and see how it reads.
> The
> > actual species is Brachylophus bulabula. It gets just one mention (in a
> > figure), and there are relations on different Fijian islands, plus
> > apparently also one iguana human-transported.
> > --
> > Geoffrey B. Read, Ph.D.
> > Wellington, NEW ZEALAND
> > gread at actrix.gen.nz (mailto:gread at actrix.gen.nz)
> (mailto:gread at actrix.gen.nz (mailto:gread at actrix.gen.nz))
> > >---- Original Message ----
> > >From: John Grehan via Taxacom
> > >To: "taxacom"
> > >Sent: Fri, Mar 21, 2025, 9:33 AM
> > >Subject: Taxacom: supposed evidence of Pacific ignuana dispersal
> > >
> > >Some of you may have seen this as it's been splashed around widely on
> the
> > >propaganda circuit.
> > >
> > >Iguanas rafted more than 8,000 km from North America to Fiji PNAS 2025
> > Vol.
> > >122 No. 12 e2318622122 https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1073%2Fpnas.2318622122&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574211023%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=HxRJ1NV7kHjr5a0H8jSWg40VxdsVChEsGUv9JJyvHOE%3D&reserved=0
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> > (https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1073%2Fpnas.2318622122&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574240295%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=%2BWKPzyU5xuL6dAK0yec6JiPsxh%2BuaVarQnuVqjAJD0k%3D&reserved=0
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> > >
> > >It's just another duplication of the same old trash. Abstract claims
> that
> > >?Here, we investigate the occurrence and timing of the greatest
> known
> > >long-distance oceanic dispersal event in the history of terrestrial
> > >vertebrates?the rafting of iguanas from North America to Fiji.?
> > Trouble
> > >with this is that it makes out that this ?long-distance oceanic
> > dispersal
> > >event? is an established scientific fact when it is not.
> > >
> > >
> > >Then they assert that ?Iguanas are large-bodied herbivores that are
> > >well-known overwater dispersers, including species that colonized the
> > >Caribbean and the Gal?pagos islands.? when there is absolutely no
> > >empirically based evidence that the Galapagos iguanas ever dispersed
> > >overwater to the Galapagos.
> > >
> > >
> > >
> > >And the central rot (as in decay) of their claims is the same as all
> the
> > >other center of origin-chance dispersal recipes: The divergence
> estimate
> > is
> > >based on fossil calibration which can only render minimum ages.
> Anything
> > >else (such as priors) is conjecture. So their timeline is erroneous in
> > this
> > >respect. The other is that their ancestral-areas analysis is simply a
> > >recipe that cannot empirically distinguish between chance dispersal
> and
> > >vicariance as either can generate the same phylogenetic area sequence.
> > >
> > >
> > >
> > >Given their calling attention to the Galapagos it seems an incredible
> > >oversight to have missed Heads & Grehan 2021 on Galapagos
> biogeography,
> > >including the Fiji connection. I've seen this before, where there is a
> > >narrow range of citations restricted to the same school of thought.
> > >Anything else does not exist. This, then, is the pinnacle of academic
> > >achievement in the US (maybe a good argument for the government
> trashing
> > >science?).
> > >
> > >
> > >Cheers, John
> >
>
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--
Dunedin, New Zealand.
My books:
*Biogeography and evolution in New Zealand. *Taylor and Francis/CRC, Boca
Raton FL. 2017.
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*Biogeography of Australasia: A molecular analysis*. Cambridge University
Press, Cambridge. 2014. https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.cambridge.org%2F9781107041028&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574288380%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata&s%2B0f7u3PquMiV43JyH5m4UzgfuOUzl9vqVLq5Xn9Y%3D&reserved=0
*Molecular panbiogeography of the tropics. *University of California Press,
Berkeley. 2012. https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ucpress.edu%2Fbook.php%3Fisbn%3D9780520271968&data%7C02%7Ctaxacom%40lists.ku.edu%7C9159da938a0042e7448308dd6a59f973%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783657574302516%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdataËDrCmeiNV%2Fz4INfdUnn3q2%2FsRdUIOrOVL%2Fu2ie6IyE%3D&reserved=0
*Panbiogeography: Tracking the history of life*. Oxford University Press,
New York. 1999. (With R. Craw and J. Grehan).
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