----- Forwarded message from andrea cardini <[email protected]> -----
Date: Wed, 10 Apr 2013 06:18:04 -0400
From: andrea cardini <[email protected]>
Reply-To: andrea cardini <[email protected]>
Subject: curves, surfaces and homology in morphometrics
To: [email protected], [email protected]
Dear All,
following from the discussion on semilandmarks,
I'd say that the whole issue of homology in
geometric morphometrics is, at least for me, far from trivial.
Many people have written about it. Some of my
favourite, and, I fear, under-read and under-cited papers on this topic are:
O’Higgins P (1997) Methodological issues in the
description of forms. In Lestrel PE, ed. Fourier
descriptors and their applications in biology.
Cambridge, UK: Cambridge University Press.
Klingenberg, C. P. (2008). Novelty and
“Homology-free” Morphometrics: What’s in a Name?
Evolutionary Biology, 35(3), 186-190.
Oxnard, C., and O’Higgins, P. (2011). Biology
Clearly Needs Morphometrics. Does Morphometrics
Need Biology? Biological Theory, 4(1), 84-97.
There's many others, and indeed plenty of refs in those papers.
In general, the morphometric descriptors one
decides to use should be functional to the
hypothesis being tested, and sometimes more may not necessarily mean better.
Semilandmarks are great tools if used with caution.
In my poor understanding of the whole issue,
sliding, for instance, improves the geometric
correspondence of those points according to
clever and elegant mathematical models, but none
of those I know are based on biology. This is why
I don't think that they "improve homology", if we
are talking about the underlying biology.
Curves or surfaces described by semilandmarks may
indeed be homologous but they're measured by
variables generated by 'discretizing' them with
points which lack the clear biological
correspondence of well defined anatomical
landmarks. What's interesting to me is whether
these 'special points' accurately map on
corresponding biological features across
specimens in a study, and that's something that I
find far from obvious. The example shown in Fig.
7 of Oxnard & O'Higgins (2009) may be a special
case or may be more common than we assume:
possibly, we just don't know for sure and that should be acknowledged.
As I said, I have a very limited experience and
understanding of an issue, which is complex and
has deep roots in morphometrics, as one can
appreciate by reading the paper written by
O'Higgins in 1997 and its extensive bibliography.
Overall, I feel as fascinated and appealed by
semilandmarks and related methods, as I feel
worried of what they may be actually measuring
and whether their use may become sometimes (not
certainly in all cases) a matter of fashion as
user-friendly software becomes available.
Cheers
Andrea
At 07:58 10/04/2013, [email protected] wrote:
>----- Forwarded message from "Singleton,
>Michelle" <[email protected]> -----
>
>Date: Tue, 9 Apr 2013 09:03:22 -0400
>From: "Singleton, Michelle" <[email protected]>
>Reply-To: "Singleton, Michelle" <[email protected]>
>Subject: RE: Why semilandmarks when I can use lendmarks?
>To: [email protected]
>
>Hi Bernd,
>
>
>
>Semilandmarks are useful when you are working
>with (presumably) homologous contours or
>surfaces that have few or no well-defined
>landmarks. To give examples from primatological
>studies (my area), the supraorbital torus,
>zygomatic arch, and calvaria  are often
>analyzed using semilandmarks. Hope this is helpful.
>
>
>
>Best regards,
>
>
>
>Michelle Singleton
>
>
>Department of Anatomy
>
>
>Midwestern University
>
>
>
>From: [email protected]
>[mailto:[email protected]]
>Sent: Monday, April 08, 2013 10:57 PM
>To: [email protected]
>Subject: Why semilandmarks when I can use lendmarks?
>
>
>
>
>----- Forwarded message from
>"[email protected]" <[email protected]> -----
>
>Date: Mon, 8 Apr 2013 13:49:19 -0400
>From: "[email protected]" <[email protected]>
>Reply-To: "[email protected]" <[email protected]>
>Subject: Why semilandmarks when I can use lendmarks?
>To: [email protected]
>
>
>Hey guys,
>
>
>
>sorry for asking such a basic question, however,
>I have to admit that I don´t understand what semilandmarks are there for.
>
>
>
>Why should I use semilandmarks when I can use
>real landmarks as well? - I have the feeling
>that I miss an important point there.
>
>
>
>Can somebody tell me what makes semilandmarks
>important and when it is reccomended to use them?
>
>
>
>Best wishes and thanks in advance,
>
>
>
>
>Bernd
>
>
>
>
>
>----- End forwarded message -----
>
>
>
>
>
>
>----- End forwarded message -----
>
>
Dr. Andrea Cardini
Researcher in Animal Biology
Dipartimento di Scienze Chimiche e Geologiche,
Università di Modena e Reggio Emilia, l.go S. Eufemia 19, 41121 Modena, Italy
Honorary Fellow
Centre for Anatomical and Human Sciences
University of Hull, Cottingham Road, Hull, HU6 7RX, UK
University of York, Heslington, York YO10 5DD, UK
Adjunct Associate Professor
Centre for Forensic Science , The University of Western Australia
35 Stirling Highway, Crawley WA 6009, Australia
E-mail address: [email protected], [email protected]
Webpage: http://sites.google.com/site/hymsfme/drandreacardini
Datasets:
http://ads.ahds.ac.uk/catalogue/archive/cerco_lt_2007/overview.cfm#metadata
Editorial board for:
Zoomorphology:
http://www.springer.com/life+sciences/animal+sciences/journal/435
Journal of Zoological Systematics and
Evolutionary Research: http://www.wiley.com/bw/journal.asp?ref=0947-5745&site=1
Hystrix, the Italian Journal of
Mammalogy: http://www.italian-journal-of-mammalogy.it/
----- End forwarded message -----
