Place in taxonomy

Stephen C. Carlson scarlson at MINDSPRING.COM
Wed Jul 3 23:21:25 CDT 2002

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
Synoptic Problem Home Page
"Poetry speaks of aspirations, and songs chant the words."  Shujing 2.35

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