Characters, etc.

[Don.Colless at CSIRO.AU]

Erast Parmasto wrote:
"In a good data matrix of (morphological) characters, what we call "character states" are actually not different states of one character, but homologous (characters)"

This illustrates nicely a problem with the term "homology" (which, let us recall, implies some sort of sameness of reference). There are (in my humble opinion!) two separate concepts here, relating to: (1) two instances of the same attribute, e.g., "red eyed", as applied to two different creatures, because they employ the same segment of a single character; or (2) two instances of different attributes, e.g., "red eyed" and "blue eyed, because they employ states of the same character.

Happily, I don't think this causes any confusion in practice - just as taxonomists regularly use "character" in at least two different ways, without it seeming to determine the quality of their taxonomy; unless, of course, they spend TOO much time playing the philosopher!



Don Colless,
Div of Entomology, CSIRO,
GPO Box 1700,
Canberra. 2601.
Email: don.colless at csiro.au
Tuz li munz est miens envirun