Talk: Paraphyletic
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In biological taxonomy, a grouping of organisms is said to be paraphyletic if it does not represent all the descendants of some common ancestor. Most schools of taxonomy advocate that groups reflect phylogeny instead, and so view the existence of paraphyletic groups in a classification as errors. Taxonomic groups that do share a common ancestor are called monophyletic.
- I'm a little confused here. The last sentence seems to indicate monophyletic means "all share a common ancestor", but the first sentence seems to indicate that paraphyletic means "does not provide complete coverage of the set of all descendants of some common ancestor". Is the first sentence instead intended to mean "contains members which may not all share the same set of ancestors"? Chas zzz brown 11:21 Dec 6, 2002 (UTC)
- Thanks for the clarification, Steve Chas zzz brown 07:51 Feb 12, 2003 (UTC)
This does not necessarily mean that older biologists meant to create them; more often it was just that they needed to have some taxonomy in order to organize the huge number of species in a way they could understand, and without modern scientific evidence, guesswork was required that later turned out to be wrong.
I don't think this is true. Older taxonomies in many cases contain groups which are obviously intended to be paraphyletic. For instance, it has long been understood that mammals and birds evolved from reptiles (making the reptiles paraphyletic), but only recently has the class Reptilia been objected to on these grounds.
- I really did not like that paragraph but wondered how best to change it. The most charitable interpretation of it seems to be at the genus level, where many paraphyletic genera have been erected because of they have been classified by overall similarity, which necessarily includes plesiomorphies, rather than by recognizing apomorphies by a cladistic analysis.
In phylogenetics, a grouping of organisms is said to be paraphyletic if all the members of the group have a common ancestor but the group does not include all the descendants of the common ancestor.
This is a tautology, any group of organisms is vacuously paraphyletic as defined here (let A be a common ancestor, let B be a parent of A, and let C be a sibling of A sharing parent B. Then C is not in the group, but it is the descendent of a common ancestor of the group, namely B). It should probably read "In phylogenetics, a grouping of organisms is said to be paraphyletic if the group does not include all of the descendents of the most recent common ancestor of all the members." I would change the page but I don't want to introduce an error, in case this isn't what the author intended to say. --A5 00:25, 26 Mar 2004 (UTC)
Another confused reader here... what does this mean?
- Groups which include all the descendants of a common ancestor are commonly termed monophyletic, although this term is sometimes taken to apply to paraphyletic groups as well, in which case they are called holophyletic.
The primary culprit is the unclear "they", but the whole sentence is as clear as mud. Should probably be broken into two carefully worded sentences. Perhaps it would be better to have three parallel definitions: paraphyletic, monophyletic, holophyletic, to make it clearer exactly how they're used and what the distinctions are. I'm not a science dunce, I promise! This just needs refining. Catherine\talk 07:06, 28 Nov 2004 (UTC)
