Caminalcules and Didaktozoa: Imaginary Organisms as Test-Examples for Systematics

Abstract

There are several artificial data sets created for theoretical considerations or didactic purposes in systematics (sect.1). Most famous are the Caminalcules (Figs. 1–4). They have been used for three decades for taxonomic exercises (mainly in numerical taxonomy) and subjected to intensive analysis (sect.2). Their “phytogeny” (“true tree”) is claimed to be representative for real organisms. Hence it was argued that the taxonomic procedures proved to be successful for Caminalcules could be used for living organisms with success as well.

The present paper analyses the “evolution” of the Caminalcules from the viewpoint of a morphologist and evolutionary biologist and shows that the Caminalcules are not representative of real organisms in many respects (sect.3): the tree topology (monophyla vs. paraphyla etc.), the character states in the stem-species, the absence of any serious problem of homologizing, the low number of convergences, and esp. the high number of living fossils. In Fig.2, the phenetic approach (overall similarity) and the cladistic approach are contrasted in easily understandable form. The “Didaktozoa” (Figs.5–7) are introduced and discussed (sect.4). They are more “handier” than Caminalcules, having only 12 terminal taxa. Also, they were created by rules most biologists will agree upon, and some problems with convergences are included to simulate the situation systematists are frequently confronted with. By giving alternative trees (Fig.7 vs. Fig.6) it is demonstrated that ingroup-analysis alone is usually not sufficient, rather that additional information from ontogeny and outgroups should be incorporated. Although not directly involved with molecular systematics, this article may be of relevance to molecular systematists as well (sect.5).