Echinoid Character Set

[Peter Stevens]

  Such a compilation will be very useful.  However, unless you can
also find a way to store the actual measurements, etc., the value of
the compilation may be less than it might be.  There are four main
reasons for this (I lifted the following from a ms.):

1. We can check earlier decisions that there were states by examining
the observations available to the authors who made those decisions.
2.  The same character may be quite properly divided in different
ways for different taxa within a larger group.  When studying the
larger group, we need to combine all the raw data from which states
were separately abstracted in smaller studies.  Combining raw data
may destroy states, looking at a subset of the raw data may suggest
additional states.
3. There is no knowing how new observations will relate to a gap that
was used to separate two states (but see 4).  Similarly, if specimens
were misidentified, or were correctly identified, but were placed in
the wrong genus (for example), observations based on these specimens
can be readily reassigned, at the same time evaluating any effects
this may have on state delimitation.
4. Gap coding is not universally accepted, and there are at present
no sound reasons for preferring one method of coding over another.
There are few studies that code the same observations in different
ways and compare the results, although Wiens has recently found
substantial topological differences after analysing data sets that
had been produced by using different criteria for coding
morphological data.  Absent such reasons and comparisons, we need to
be able to code observations in different ways, and for this we need
access to measurments.

best of luck!

Peter S.


>In the spirit of the Tree of Life Initiative, and to facilitate
>communication among researchers interested in taxonomic or systematic
>analyses of regular echinoids, I would like to compile a morphological
>character-set potentially suitable for systematic analysis of any regular
>echinoid group.
>
>As characters are submitted, I will compile a list (citing the source
>(author and/or publication) of the characters).  Once the character-set is
>complete, I will make it available on appropriate list-servers and any
>other media in which it might be suitably presented (e.g., the Echinoderm
>Newsletter).
>
>If you are interested in commenting on, or contributing to this character-
>set list, please reply to me (off-list) at bneill at bestweb.net.  I will
>gather the addresses of those interested parties and proceed to compile the
>character-set.
>
>Thank you and my apologies for cross-postings.
>
>Bruce Neill, Ph.D.
>bneill at bestweb.net