Taxacom: supposed evidence of Pacific ignuana dispersal
John Grehan
calabar.john at gmail.com
Sun Mar 23 18:40:55 CDT 2025
2025
Geoff?s latest comments in quotes below.
"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."
No, that is not all that the paper is about. It's also about biogeography.
?Really, of course you are free to criticize?
Agreed ? I am free to criticize their paper for transmogrifying minimum
ages into actual or maximal to preclude earlier origins. I am free to
criticize the paper for analyzing areas that have no empirical existence. I
am free to criticize the paper for creating dispersal scenarios using a
recipe that cannot empirically distinguish between vicariance and chance
dispersal.
?but I don't think these authors deserve your scorn.?
Maybe, maybe not, but its irrelevant. Science is not the study of
reactions, but the study of evidence. And in terms of evidence this paper
falls rather short.
?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.?
Actually they do not include ?similar scenarios?. They do not address the
allopatry of the agamid-iguanid sister groups - which is very pertinent
when inventing chance dispersal to supposedly explain part of that
allopatry.
?It's a molecular paper. Let's assess it on that basis.?
Did I not? There are hundreds, if not thousands of biogeographic studies
supporting vicariance using molecular evidence. Only in this case the
authors chose to ignore that.
?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.?
There is no progression in center of origin-chance dispersal approaches
based on transmogrified fossil ages, areas that do not exist, and recipes
that cannot provide empirically based evidence of vicariance or chance
dispersal. There has been no progress in center of origin-chance dispersal
biogeography from the time of Darwin, so why expect anything different in
the future? After all, center of origin-chance dispersal fails abysmally
when it comes to making any novel predictions about geological history, let
alone any that have been independently corroborated.
Cheers, John
On Sun, Mar 23, 2025 at 5:36?PM 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%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985434485%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Nx3HRFLsJvE3CkBHPcgq4afNPANAc2RkXsu%2FaGXAq%2B4%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%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985451124%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdataªyB9o7qtG%2BMI5osCT0P06loL%2BT0qG5Q972gvDTIgws%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%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985465550%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata]agfV18IM2xDOQnSpG5%2BqxtTOIOdsXgdxs2g2e7PUs%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%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985479076%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=w4I0OnN7bjoOMle0Q0yF44h%2BRuTJn5z5SufO76aG3Xk%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%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985492520%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=BZFFMHrOwlN5BC6kKRedMsSedprjvU460G8N5xUoFAM%3D&reserved=0
> (https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1073%2Fpnas.2318622122&data%7C02%7Ctaxacom%40lists.ku.edu%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985504439%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Bty%2BdJDZYYZ1bjm8DuzXMdO2A1LGb%2FQ7Tl9TAuXd05E%3D&reserved=0)
> > (https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1073%2Fpnas.2318622122&data%7C02%7Ctaxacom%40lists.ku.edu%7Cfa644dee43e14193fd1f08dd6a643e97%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783700985516211%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=B%2FUEIdClH5Ah3Uq6Gop4ssheqC%2FUm%2FofLfe7crVmVGU%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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