>>CK,

>>I recently received a copy of the MP consensus tree for the new mtDNA study. On a large scale, the result duplicate and confirm Javier's results of three major groupings or subclades.>>

>>Richard F. Hoyer



The terms clade and subclade are the favorite jargon of the cladists. Cladists are so named because they are obsessed with "discovering" clades, or groups that consist of a single common ancestor and ALL of the descendant species of this common ancestor. The term "all" is emphasized because if some of the descendant species of this group are excluded, the cladists no longer consider the group a clade, or a monophyletic group. The term clade has a different meaning for traditional, or Darwinian taxonomists. The traditional or Darwinian taxonomists consider Reptilia, for example, a clade because all species within Reptilia share a recent common ancestor, even though not all descendant species of this recent common ancestor are included. Cladists call such groups paraphyletic, and they will seek to either splinter or lump without regard to morphological differences until there are no more paraphyletic groups in their taxonomy.



The "clades" and "subclades" delimited by mtDNA data differ from the morphotypes within the rubber boa. For example, if the 2 large morph boa subclades are given subspecies recognition and the small morph boas of Kern County are classified as umbratica in a 3 subspecies arrangement that I favor, the small morph boas (umbratica) would become a paraphyletic taxon. The cladists would almost certainly not accept such an arrangement, because they despise paraphyletic groups, even though such a taxonomic arrangement would inform us that the small morph represents the ancestral condition and that the large morph populations were derived independently (budded) from the small morph snakes.



The current 2 subspecies or 2 species taxonomic arrangement of umbratica and bottae is unsatisfactory because bottae contain a mixture of 2 lineages of independently derived large morph snakes and also a population of small morph Kern County snakes which have changed very little (if at all) since becoming geographically isolated from the Southern California (umbratica) populations. The 2 taxa arrangement also tells us nothing of the existence of the large morphs within the northern subclade, and it tells us nothing about the separate evolutionary origins of the 2 large morph populations. Instead, it misinforms us into believing that the Kern County boas are different from the dwarf form found in Southern California and that they more closely resemble the large morph snakes in the Pacific Northwest and Sierra Nevada Mountains.



Nevertheless, the cladists would favor the 2 taxon arrangement because such an enlargement allow them to recognize taxa that consist of a single common ancestor and all of its descendant species. In other words, such an arrangement allows them to avoid recognizing taxa that are paraphyletic.

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