Place in taxonomy

[pierre deleporte]

Comment to Stephen Carlson (text below):

Methodologically, I use "heritable" the way you do: it means "likely to 
carry relevant historical information for reconstituting a history of 
descent of characters with possible modification".
Applications in the study of manuscripts is a classic (maybe preceding the 
advent of cladistic methods in biology). It should work, given a series of 
assumptions for the process (like not too much horizontal transfer or 
insertions-deletions I presume !).

There is no doubt that location MAY be inherited from parents. No doubt 
also that it MAY change. A general objection to the routinely use of 
spatial data for infering phylogenetic relatedness is (as stated by Tom 
Dibenedetto) the complete impossibility of discriminating between reliable 
and misleading silmilarities. "Standing at that place at this time" is the 
same for a contemporaneous australian kangaroo, horse, and camel. Such 
spatial data offer no possibility of further analysing the details of their 
similarity, when genetic sequence data are open to consideration of 
secondary structure for instance, and morphological traits may offer 
structural or developmental details for investigation.

But Robert Mesibov makes a good point in underlying that "spatial data" may 
sometimes be more complex and informative than simply "standing here and now".

Pierre


A 23:21 03/07/2002 -0400, vous avez écrit :
>At 04:24 PM 7/3/02 +1000, Robert Mesibov wrote:
> >In on- and off-list responses to my posts there are two recurring points:
> >
> >"You shouldn't weigh biogeographical evidence more heavily than character
> >evidence when you build a phylogeny." Of course not, and I never suggested
> >you should.
> >
> >"You shouldn't trust biogeographical evidence in building a phylogeny,
> >because location isn't heritable, and a phylogeny (a history of descent) is
> >necessarily all about heritable characters."
> >
> >The latter statement is flawed because it confuses two different things:
>
>I'm using this post as a jumping off place for clarification on
>what is meant by "heritable".  Is it co-terminous with "genetic",
>or could "heritable" be a broader concept that relates to any
>character or trait that comes from the parent?
>
>If "heritable" is a broader concept than "genetic", then spatial
>or temporal characters could qualify as non-genetic "heritable"
>characters.  For example, offspring (in most organisms) have the
>same location as their parents.  E.g., two polar bears living in
>the Arctic circle do not produce a cub in Africa.  Same for
>temporal/stratigraphic characters.
>
>Organisms do move from one location to another, but how is this
>philosophically different from changes in states of (genetically)
>heritable characters due to mutation?
>
>Two relatively unrelated organisms can occupy the same location,
>but how is this philosophically different from homoplasy in
>genetically heritable character data, esp. in molecular data?
>
>I certainly understand that in some, many, or most cases spatial
>and stratigraphic information can be much more "noisy" than
>traditional characters, which may counsel against their
>inclusion in the analysis, but I cannot understand the a priori
>objection to inclusion of spatial and stratigraphic evidence.
>
>Even if it is conceded that such evidence is generally noisier
>than traditional character evidence, they may not be so in the
>particular case.  Furthermore, cladistic methods, including
>maximum parsimony, are fairly robust to noisy data.
>
>If "heritable", however, means the same as "genetic," then what
>would be a good term for the broader concept for a character
>that comes from the parent?
>
>Stephen Carlson
>
>P.S. I am writing, not as a biologist, but as a textual critic
>who has been researching the application of cladistic methods
>to problem of determining the filiation of medieval manuscripts.
>However, for my data set, I am much more interested in time
>rather than space due to the quality of my evidence.
>--
>  Stephen C. Carlson                       mailto:scarlson at mindspring.com
>Synoptic Problem Home Page   http://www.mindspring.com/~scarlson/synopt/
>"Poetry speaks of aspirations, and songs chant the words."  Shujing 2.35