[Taxacom] Panbiogeography and geological 'facts'

[John Grehan]

Since Ziv appears to have declined to back up his claim that the claims by
Waters et al, are 'solid', which seems to be a classic technique (i.e.
throw out accusations without providing supporting detail) used by some
politicians. This sort of leaves the potential for scientific discussion
rather mute. So to at least be of some assistance to those interested, I
refer briefly to an example involving geology:

Waters et al noted:

“Application of the panbiogeographic approach to the Chatham Islands biota
led to claims that ancient tectonic evolutionary processes stretching back
over 100Ma explained its apparently composite nature with respect to the
distribution of relatives on different parts of the New Zealand mainland”

This they refute by the assertion that:

“Subsequent geological and palaeontological analyses, however, clearly show
that the islands themselves were completely submerged until less than 10Ma”

To this, Heads (2015) responds (and note this is an example of responding
to critics and not avoiding the accusations):

“In fact, geologists have agreed that islands existed in the area currently
occupied by the Chathams before 10 Ma, but that there were no emergent
islands from 6 until 3 Ma”

This might seem to corroborate Waters et al, at least for a time period,
but this then conflicts with molecular data (that panbiogeographers are
supposed to ignore) as noted by Heads:

“Nevertheless, on the basis of older clock dates for various plants endemic
to the Chatham Islands,

Heenan et al. (2010) suggested that islands also existed in the region
between 6 and 3 Ma.”

In other words, molecular folk also are prepared to support panbioeographic
argument for the existence of islands even without geological evidence!

And to cap it all off, Heads offers further geological information that
would be consistent with metapopulation survival of biota in the immediate
vicinity over these time periods:

“In addition to the islands that geologists have accepted in the Chathams
archipelago before 10 Ma, and the islands that Heenan et al. (2010)
proposed there between 6 and 3 Ma, there is now excellent evidence for
many, now-submerged seamounts (former islands) around the Chatham Islands
and the Chatham Rise, lying between the islands and the New Zealand
mainland (Rowden et al. 2005). Multibeam surveys of seamounts around part
of the Chatham Rise have shown that the largest volcanic cones are ~2000 m
in diameter and that most of the cones have flat tops (Collins et al.
2011), indicating erosion to sea level before subsidence. Waters et al.
(2013a) argued that: ‘. . .multiple independent lines of evidence clearly
indicate that the modern Chatham Islands biota was established by
trans-oceanic dispersal [from the mainland]’ (p. 496), but they overlooked
the seamounts.”

I welcome any criticisms of panbiogeography, but I would naturally prefer
that when Ziv and others repeat claims in the literature, they at least
take the time and trouble to explain why they consider such claims 'solid'
with respect to how such claims have been addressed by panbiogeographers.
Failure to do so obfuscates the real nature of the debate. In Ziv's case,
he says he has read the literature, so why not mention responses such as
this and why they are, in his opinion, wrong? What could be harder than
that? In this example I have illustrated why I am justified in calling the
geological claim by Waters et al untrue and a fabrication. And I have
provided detail. Can Ziv do as much?

Cheers, John