Taxacom: supposed evidence of Pacific ignuana dispersal

[John Grehan]

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%7C106c5d33480b4196b1c008dd67ee7220%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638780996010127910%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=7Z8I9R3ptxScRO0FH8jBqReeaZUvqzBzc1Pog%2BbLvKA%3D&reserved=0

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


I
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