[Taxacom] scientific predictions concerning Wallacean marsupials and primates

[JF Mate]

Michael/John,

you make a distinction of dispersal that is tailored specifically to
make panbiogeography unassailable. You define a "normal" dispersal,
the one that you like, as the dispersal that  "...can be observed
every day. The distribution of every species changes (slightly) every
day because of dispersal. ... in the weeds that colonise a garden, or
in an albatross crossing the Pacific, and takes place by normal,
observed means of dispersal." This distinction has several in built
assumptions that you haven´t discussed, either because you assume them
to be self-evident or, rather, because the distinction may not be as
clear as you hope.

The obvious one it to ask what is meant by "normal", "observed",
"slightly", etc. All these terms are very human but very vague and I
can´t see how one cannot simply say "a little more".

The second is the assertion that "it doesn´t lead to speciation". Not
only do I not understand exactly what is meant by this but further you
neither provide a basis to for your assertions nor examples to support
this. I have briefly mentioned these in the case of Polygonia
(butterflies being a well researched group), but a much better example
is the phylogeny of Vanessa (Wahlberg & Rubinoff, 2011) that John
aludes to when he mentions V. vulcanica (although it is further
removed in time). He assumes that this is an example of vicariance
when dispersal provides a simpler explanation for lineages such as
indica. The branch lengths within the V. indica group are much too
shallow, not just the stems but the tips as well, and the individuals
within each species have divergences which are very low compared with
other Vanessa species, which suggests a fast and very diversification,
more likely the result of recent climatic events rather than
geological ones. In particular the placement of this clade is derived
with respect to the basal clades (Holarctic V. atalanta and Hawaiian
V. tamemea) and both clades sister to the Ethiopian V. abyssinica,
which clearly suggests dispersal out of Africa, and not some
mysterious, and much more ancient, Tethyan vicariance event.

Furthermore, Wahlberg & Rubinoff find that highly vagile species have
highly restricted sister taxa. This demonstrates that, gene flow on
its own is not sufficient a factor to explain allopatric speciation;
and that vagility can be highly labile. Hence current dispersal
ability of a lineage is not in itself enough to rule out dispersal as
a mechanism. This examplifies why a priori assumptions about dispersal
ability (what I suspect underpins your distinction between normal and
LD dispersal) can lead you astray and how "normal" is anything but.

In regards to the Waters et al paper that Ken has kindly shared, it
may be harsh, but your rebuttal is similar to previous answers of
yours so it is difficult to see how it changes anything then and
since. It is a fact that it is futile to constructively argue when any
evidence presented by side is summarily dismissed as inherently
tainted by their limitations while you ignore your own problems. I
particularly find troubling the idea that falsification is
philosophically problematic to you and that your solution is to seek
"... corroboration – either there is subsequent evidence that is in
agreement or there is not. In the latter situation one is confronted
with unresolved conflict for which there is no objective recipe to
make a choice.". By rejecting all the other avenues that can possibly
test for mechanisms, your strictly orthodox interpretation of
panbiogeography has anchored the field out of science. It is
historical but with a bias of simply seeking to confirm what it
"knows" or create knowledge by imagining as yet unknown geological
events. Odd or contradictory examples are either fitted by a
combination of denial (of LDD, of molecular markers,), imagination
(lumping a few dispersal tracks and then assuming vicariance is a real
risk), and labelling (calling non panbiogeographers "dispersalists" as
a way of denying vicariance to anybody but panbiogeography); or simply
ignored. Only when you lose that anchor can you hope for conciliatory
discourse.

Jason