[Taxacom] panbiogeography conversations

[John Grehan]

*I thought it desirable to comment further on the nature of responses. When
I am presented with assertions about panbiogeography that lack specific
detail I tend to respond in kind - confirmation or rejection. In that way I
avoid guessing what is intended by such assertions. But if specific details
are provided I am certainly happy to look into matters in a more specific
way.*

*So when Ziv claims that the points made by Waters et al are "solid" there
is not much I can say without knowing what points are being referred to and
why those points are considered to be solid. Getting to that specificity
allows for a more developed conversation, and I am looking forward to
seeing what Ziv presents in support of his case on 'solid points'.*

To explain a bit further with respect to a couple of comments by Ziv:

*"As presented in recent studies, the panbiogeographic approach involves
little more than mapping species distributions and drawing lines (tracks)
connecting them.”*

I said this is not true because it is indeed not true. If one reads the
panbiogeographic literature one sees that the method also involves
examining the spatial characteristics of allopatry and tectonic
correlations to name a couple. To overlook that is somewhat strange.

*In contrast, panbiogeographers have proposed scenarios that seemingly
dismiss all other data regarding the history of life on earth" (p. 2)*

I said that panbiogeography does not dismiss "all other data" because
again, I am not aware of any data being dismissed. What is often dismissed
is the misrepresentation of fossil calibrated molecular divergence
estimates as actual or maximal ages. But that is not the same as dismissing
molecular divergence estimates. Rather, they are accepted, but only as
minimums. Earlier critiques have tried to claim that
panbiogeography ignored fossils, but somehow such claims ignored the
inclusion of fossil data from the time of Croizat through the present.

*"When panbiogeographic hypotheses. . . conflict with data from geology,
paleontology and molecular genetics. . . panbiogeographers tend to dismiss
these other information sources as unreliable" (p.2).*

I said this was a fabrication as it just does not ring true with what I
know of panbiogeography studies. All data from geology is accepted. What is
not accepted are speculative extrapolations such as claims of complete
inundation of a landscape when there is no evidence of such. As above,
paleontology is used and incorporated where such information is available
(see some good examples in the study of Nothofagus by Heads). And for
molecular genetics - a bizarre claim given the 2012 book by Heads
(preceding Waters et al 2013) titled 'MOLECULAR panbiogeography of the
tropics' (my emphasis), and of course the many, many other studies using
some very effective molecular systematic data.

So, I hope that bit of elaboration will help some appreciate some of the
ironies.

John Grehan