I look forward to reading it. I am particularly interested since it was
probably your 2011 paper with Phillip (Mitteroecker and Bookstein, Evol
Biol 38:100-114) which advocated its use for ordination and has resulted in
its current widespread use, but which you address in an amusing way in this
current paper in figure 10 and with the term "less inappropriate" than CVA.


On Tue, 14 May 2019 at 13:32, MORPHMET <> wrote:

> Dear MorphMetters,
> Some of you may have been in the auditorium in the Department of Botany,
> University of Vienna, back in March when Philipp Mitteroecker and I were
> the two scheduled discussants for the conference "GMAustria19" on
> applications of geometric morphometrics.  Several of the papers delivered
> there used between-group principal components analysis (bgPCA), and after
> each of those papers I mentioned in the course of my commentary that bgPCA
> was fatally flawed in applications to most GMM data sets and should NEVER
> be used here. In my keynote address, which closed the meeting, I had one
> cryptic slide about this assertion, with an example that flashed on the
> screen but was immediately replaced by the next slide.
> The typical response to both my own talk and my criticism of the talks of
> others, as far as bgPCA was concerned, was along the lines of "Hunh?" or
> sometimes "What are you blathering about this time? Isn't bgPCA in the
> standard toolkit?" I answered that the Bookstein paper they should read was
> just then being written, as one of a pair jointly arising from
> conversations with Andrea Cardini, Jim Rohlf, and Paul O'Higgins following
> an original hunch of Cardini's, and that my argument would be pretty
> convincing once it was actually written down.  The claim isn't that people
> are using bgPCA incorrectly. They're using it according to the published
> formulas, yes, but the method itself yields biological nonsense much too
> often.
> That was March.  In April, two different articles in Nature (one by
> Detroit et al., one by Chen et al.) buttressed claims about sister species
> of Homo sapiens using the bgPCA method, and so suddenly it became clear
> that we authors had to do something quickly lest this become an epidemic of
> bad biometrics. So we accelerated our writing. My paper was the first to be
> finished, probably because it is a single-authored item by an emeritus with
> no other obligations, and it seemed like a good idea to upload the final
> draft to even before submitting the paper, so
> that any letter to the editors of Nature could include a link to  the
> argument as to exactly WHY bgPCA is nearly always unsound and its
> inferences invalid for applications in contemporary GMM.
> That is the draft that has just appeared as
> For those of you who were at the March meeting, this is the argument
> (complete with formulas) defending my stern condemnation there. I won't try
> to summarize it in this morphmet note -- if you're interested, just read
> the abstract on page 1 of the link.  For those of you who have already
> published bgPCA analyses, you know who you are -- my paper argues strongly
> that you need to go back and revisit the inferences of those papers in a
> mood of much more intense multivariate skepticism.  For the rest of you,
> please consider this draft manuscript to be a wake-up call. A technique
> that has appeared in dozens of papers and that was, alas, specifically
> praised by Mitteroecker and Bookstein personally (back in 2011) could
> nevertheless, when examined closely (for the first time!), turn out to be
> algebraic garbage when applied to data sets where there are far more shape
> coordinates than specimens. But isn't that the usual situation in GMM these
> days?
> As always, I welcome all responses, both positive and negative. The
> biorxiv posting is permanent, but there is plenty of time for me to make
> changes before the paper is published (at present it has not yet even been
> submitted anywhere), so feel free to try to find the flaws in my argument.
> But I hope you will want to try some of these simulations on your own
> before you argue against mine. You will also want to study the companion
> piece by Cardini, O'Higgins, and Rohlf that should likewise be available
> for download before too long.
> Fred Bookstein
> --
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Ian Dworkin
Department of Biology
McMaster University
Office phone 905 525 9140 ext. 21775
Lab phone 905 525 9140 ext. 20076

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