Patrick Alexander wrote (quoting me; numbers added):

`Well yes, but natural objects that are likely to come up in conversation (e.g. species, or clades with distinctive apomorphies) might as well have names, otherwise communication becomes a bit laboured. That's why we have taxonomy at all. '

(1) Exactly--and that's why paraphyletic taxa are often the best solution.

`To qualify my point about giving up higher ranks, that's not necessary in this case because one could use the widely accepted rank of subgenus for Pseudacris. But what you usually see when people use subgenera is that they feel compelled (under the Linnean straitjacket) to assign every member of the 'split' genus to one subgenus or another, which usually creates at least one more paraphyletic (i.e. imaginary) group.'

(2) And there's another problem solved by using paraphyletic taxa.

`Same with 'species groups'; how often do you see people defining a bunch of monotypic 'species groups' in a large genus?'

(3) Actually, I'm not sure I've ever seen that.

`Even at this informal level of classification, the Linnean habit makes people do strange and pointless things, and then medieval-minded pedants have something else to argue about when they've settled the angels-on-pins question (or applied radical epistemic doubt to questions of their own and each others' eye colour). If we stick to naming groups that have some evidence for monophyly, there's no need for redundant ranks and we can get back to discussing biology and evolution.'

(4) From my experience, if we stop worrying about monophyletic taxa we can get back to biology and evolution. Giving up on a comprehensible hierarchical naming system, on the other hand, seems like it'd just be pointlessly confusing.


My replies:
(1-2) What advantage does paraphyly have here? It always obscures actual relationships when these are known, and it is purely arbitrary what parts of the clade are excluded.

(3) I try to avoid groups with unwieldy numbers of species per genus, but the Australian skink genera Ctenotus and Lerista are examples where a species-group classification has been used including various monotypic 'groups' (e.g. in work by Storr where phylogeny was not a consideration).

(4) Cladistics IS a comprehensible hierarchical naming system; or what part of monophyly don't you comprehend? Recognising paraphyletic taxa involves arbitrarily and subjectively jacking up subgroups of a clade to a higher rank, adding 'information' of dubious value and deleting true information about their genealogical relationships. Just because it has been done by default since before Darwin was born, doesn't mean it makes any sense, or is intuitively more satisfying than monophyly. You may find it so, but I don't.
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John D. Scanlon
Riversleigh Fossil Centre
Outback at Isa
Mount Isa, Queensland, Australia

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