Taxacom: supposed evidence of Pacific ignuana dispersal
Geoff Read
gread at actrix.gen.nz
Sun Mar 23 16:36:13 CDT 2025
2025
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%7C0258fbd2a5ce419b142108dd6a52c3e6%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783625930400386%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=fLIYp1V1D24uudEmZ5gkMWZBWJok6WDAxN1AqUpJ47I%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%7C0258fbd2a5ce419b142108dd6a52c3e6%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783625930415590%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=pu8pwpcJmnJLk21S9pVmdiKmjHkEV3y%2F4YRy9wA8SwY%3D&reserved=0)
> (
>
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> )
> 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%7C0258fbd2a5ce419b142108dd6a52c3e6%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638783625930442168%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=KxdYGtdr9aQ9efh0DbrzMzAruxkQ9m1km2zYhjJyZfI%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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