[Taxacom] more on iguanas

[John Grehan]

To the biogeographic hobbyists: in my opinion, the primary problem of the
molecular age underestimate papers is not even so much about their
misrepresentation of fossil age calibration, but the way this technique
lets such authors escape from any responsibility to be familiar with
biogeographic patterns in general. After all, if each individual taxon has
its own history of 'chance' dispersal, then there is no need to see any
connection with the biogeography of any other taxon or the possibility of
tectonic correlations. In effect, an intellectual curtain is drawn over the
biogeographic stage. What is not seen, does not exist. For the iguanas, for
example, there seems to be no comprehension of the basic distributional
facts as noted in Heads & Grehan (2021): "The Iguanidae and their sister,
Agamidae (with Chamaeleonidae), are almost perfectly allopatric, and this
is consistent with the origin of each clade more or less in situ, by
vicariance in a global ancestor (Heads, 2014 p. 119). In this model,
Iguanidae did not cross the Pacific in either direction. The origin of the
trans-Pacific affinity is explained by breaks in a global ancestor at sites
that correspond with the western margin of the Pacific plate. The only
dispersal required in either Iguanidae or their sister group is in or
around Madagascar, where the two clades overlap." I do hope the critics on
Taxacom make due note of the reference to the evidence for dispersal here!
But of course, it is not the imaginary conception of 'chance' dispersal,
but ordinary ecological dispersal (an observable phenomenon) responsible
for range expansion. The real biogeographic issue has never been about
contesting vicariance against dispersal [which has generated the trite
conclusion that both are involved in different taxa], but coming to an
understanding about how the two processes are interrelated in the evolution
of distributions. Croizat's work was, in my opinion, the first substantial
effort to accomplish that - by making reference to the by far greatest
biodiversity resource available - the distributions of animal and plant
taxa that are made evident through the combined sciences of taxonomy,
systematics, and geography.

As for my characterizations sometimes being seen to be 'over the top', I
suppose they might be. Perhaps from now on I will just refer to such papers
as 'really, really, really terrible'. Hope that will be a widely acceptable
expression of an opinion. And of course always, with reference to why that
opinion is reached, since how one reaches an opinion in science is more
important than the opinion itself.

Interesting that those who are so outraged by language are evidently not
able to come to the table with responses to questions about their
assertions (as in recent questions by Heads). I think that says a lot.

Cheers, John Grehan