Brummitt on paraphyly: a response

out any being paraphyletic is a logical absurdity [impossibility]" (2002: 33, 40): "If we are classifying all the products of evolution, i.e., the whole evolutionary tree of life, every taxon we recognise must make another taxon paraphyletic. That is a simple logical fact". To illustrate this fact, Brummitt offered a phylogenetic tree (2002; Fig. 1, top). He did not explain the circles and the lines that interconnect them, but each circle may be seen as a taxon, and each line as an ancestordescendant relationship between two taxa: "The whole diagram is one clade, and the dark circles together form a.lesser clade within the larger clade. It doesn't matter what rank we are talking about, so, just for the sake of convenience, let us think in terms of genera. If I call all the dark circles one genus defined by the characters at 1, then the open circles must be a different genus. But then the genus of open circles is paraphyletic. " (Brummitt, 2002: 33). He refers to some circles as ancestors and others as descendants, and the whole as "a diagram of what actually happened in evolution" (p. 37). He does not consider the possibility that the open circles might comprise more than one genus, but he asserts that the circles "have remained comparatively little changed or unchanged-a situation that has arisen millions of times in evolution" (p. 33). Part of Brummitt's repeated message (Brummitt, 2002) is a challenge: "Until somebody can draw for us a phylogenetic tree.divided fully into Linnaean taxa without any being paraphyletic, we will continue to believe that our arguments on the inevitability of paraphyletic taxa are correct (Brummitt & Sosef, 1998). That was three years ago. We have had no takers. The offer is still open". In 1918 such a phylogenetic tree of this type was published by Daniele Rosa (pp. 137-138) with the following remarks: "The following scheme [Fig. 1, bottom] . represents the connections of affinity between the species of a group, such as they would be if the species were the result of dichotomous speciation. Having before us 32 terminal species, represented by the black dots above, we would be able to make four groups (such as genera): A, B, C, D. "It is clear that, even without paleontological knowledge of the connections, an adequate knowledge of the morphology of these species would suffice to indicate that genus B is more closely related to genus A than to genus C; and that, before grouping the 32 species into four genera, it would be necessary to group them into two 'supergenera' or subfamilies: AB and CD. And within each genus it would be possible also to recognise subgenera and even smaller groups of more closely related species". "If this scheme corresponds to reality, one may conclude that the distinction between groups of equal taxonomic rank cannot be arbitrary; and also that the distinctions are not caused by gaps in the system, gaps produced by extinction. Even in the absence of extinction, the distinctions would be quite clear. And while it might be arbitrary to consider group A a genus, no good systematist would ever combine some species of group C with AB, and the other species of group C with D". Rosa's scheme may be used to illustrate the classification of the eucalypt group, which includes the genus Angophora Cavanilles, 1797 (13 species)-corresponding to Rosa's group B. Most remaining eucalypts have traditionally been placed in the genus Eucalyptus L'Heritier, 1788 (700+ species)-Rosa's groups A+C+D. Eucalyptus was eventually found paraphyletic, with bloodwoods and ghost gums (100+ species), subgenera Corymbia and Blakella (Pryor & Johnson, 1971), most closely related to Angophora (Ladiges & al., 1995; Udovicic & al., 1995). The paraphyly was rectified (Hill & Johnson, 1995) simply by recognising bloodwoods and ghost gums as one genus, Corymbia-Rosa's group A-leaving Eucalyptus with fewer species (600+)Rosa's group C+D. Recognising Corymbia as a genus does not create paraphyly but rather eliminates it by making Eucalyptus monophyletic. For Brummitt, however (Brummitt, 2002: 33), "As soon as we assign a rank to a group, we create paraphyly".