HOMOPLASY, CHARACTER FUNCTION, AND NEMERTEAN SYSTEMATICS

We question recent claims that cladistic analysis is inapplicable in n emerteans (phylum Nemertea) due to a supposedly high degree of converg ence. We further argue that terms like convergence and parallelism are historical sayings and only make sense in a phylogenetic context. The refore, an approach aiming to produce phylogenetic hypotheses cannot b e rejected on the grounds of a high degree of convergence before the a ctual hypothesis. Convergence is not an empirical observation, but a c onclusion made after an analysis. We also discuss the view that knowle dge of a character's function is a prerequisite for phylogenetic analy sis and conclude that this is an invalid approach. Function, like any other way of sharpening our observations, helps in formulating non-phy logenetic hypotheses of homology, but the crucial test is congruence w ith other characters on a phylogeny.