Willem Heijns wrote:In my opinion it is interesting, Tachymarptis (btw: why would Cichlid Room Experts want to hide behind a nickname?).
To me it is quite logical to try and define taxa as natural groups.
After all it reflects history and relationships in nature.
Saying that in Linnean nomenclature it is impossible to do without paraphyletic taxa can be just as dogmatic.
In this case the close relationship between Aequidens and Cichlasoma at least calls for a discussion about wether to keep these two genera apart or join them into one. What do you think?
Willem Heijns wrote:
Another important factor is speed. Speciation takes time. I believe that most of the phylogenetic studies are studies of a situation (a moment in time) reflecting the current relationships between species (and higher taxa). That is probably why none of these studies (as far as I know) designates extant species as ancestors or descendants of other extant species. All studied taxa are terminal taxa and all we can do is make statements about the relationships between those terminal taxa and their hypothesized ancestors.
Willem Heijns wrote:Thanks for your reply Patrick.
But if the isolated population is larger (maybe even as large as half of the original population) it gets more complicated. Which of the two resulting populations is the ancestor? What if both populations change (considerably)?
Tachymarptis wrote:It is a dogmatic perversion of cladistic methodology to absolutely want to suppress paraphyletic taxa
Tachymarptis wrote:You will find as many examples as you want. Species give birth to other species, so unless they vanish completely, species are paraphyletic taxa. The reasoning is same for genera, which are, or are to become paraphyletic taxa if they do not disappear. For higher taxa, you could possibly (with great difficulties) keep them only as clades, but all ranks become obsolete, taxa become simple matryochka dolls with very few significance for use by human mind (hence Juan-Miguel's remark, which is shared by many people).
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