PRIMARY HOMOLOGY ASSESSMENT, CHARACTERS AND CHARACTER STATES

We discuss contrasting approaches to cladistic character definition an d thus to cladistic data matrix compilation The conventional approach considers character states as alternate forms of the ''same thing'' (t he character). A review of the challenges to this convention is presen ted, and their implications evaluated. We argue that the recognition o f structures which are alternate forms is a vital stage of primary hom ology assessment and is equivalent to the conceptualization of a trans formational homology. Such a view complies with the demand that charac ters are independent and that character states are hierarchically rela ted. We identify one justifiable solution to the inapplicable data cod ing problem (coding for organisms which have red tails, blue tails or no tails), and show that alternative approaches to character definitio n support spurious solutions which deny the relation of structures whi ch are ''the same but different''. We propose that the term character can be defined, in a cladistic context, as the descriptive label refer ring to a transformational homology evidenced by the similarity criter ion. (C) 1997 The Willi Hennig Society.