Talk:Evolutionary grade

Here's the deal...

Consider the difference between paraphyly and polyphyly. For all the debate, it is agreed upon that polyphyletic taxa are entirely unacceptable, whereas many (but not all) experts agree that paraphyletic grades should sometimes be accepted and subsequently ranked by taxonomic commissions (given secondary loss of otherwise monophyletic derived traits). It's almost like a number line, in that biologists/taxonomists disagree on just how limited the limited circumstances when paraphyletic (but never poly) grades are acceptable in formal taxonomy really are. Very few are completely at one extreme or the other.

Again, though, polyphyletic as opposed to para is never ever acceptable in formal taxonomy. If you were to go back in a time machine to before terrestrial vertebrates evolved (random example), you would find that the now-paraphyletic Grade Superclass Pisces was monophyletic back then. The same can not be said for a polyphyletic group as these are totally arbitrary (consider the case of Protista). So, in essence, it must always be the case that a taxon either still is or once was monophyletic. The debate (which the Article already begins to cover) is over precisely how often the latter "once was monophyletic" should satisfy formal taxonomic criteria, and the Article should clarify this nuanced matter. The Mysterious El Willstro (talk) 07:26, 18 October 2013 (UTC)

There's actually an additional subtlety. A paraphyletic group is a monophyletic group lacking one or more monophyletic groups. The acceptability of paraphyletic taxa (for those who accept them at all) seems to depend on the number of excluded groups. Singly paraphyletic taxa are the most acceptable. Peter coxhead (talk) 12:51, 18 October 2013 (UTC)

Which is sister to tracheophytes?

The cladogram clearly shows hornworts sister to tracheophytes (vascular plants), with mosses more distantly related, but the text says "mosses closest to vascular plants". Which is correct? Please somebody who knows for sure, fix this discrepancy? 198.144.192.45 (talk) 07:22, 25 March 2015 (UTC) Twitter.Com/CalRobert (Robert Maas)

Update: I checked with OpenTreeOfLife, which seems to say the correct cladogram is: Embryophyta = (mosses + liverworts ) + (hornworts + Tracheophyta). If my reading is correct, and the OpenTreeOfLife itself is correct, then the cladogram needs a small fix and the text also needs correction. 198.144.192.45 (talk) 07:52, 25 March 2015 (UTC) Twitter.Com/CalRobert (Robert Maas)

The text was wrong, and I've corrected it. The source given clearly says that hornworts are the sister of vascular plants. However, more recent research has produced different results: see Bryophyte#Classification and phylogeny for a more detailed discussion. As of March 2015, either the cladogram shown or one in which the bryophytes are monophyletic can be supported by reliable sources. I don't know where OpenTreeOfLife got its tree from. Peter coxhead (talk) 09:08, 25 March 2015 (UTC)

Ah, thanks for fixing the internal discrepancy, and for explaining some of the unresolved issues, and for referral to the other article which explains pretty nicely. Per that article, I understand that each of the four groups (Marchantiophyta (liverworts), Bryophyta (mosses) Anthocerotophyta (hornworts), tracheophytes (vascular plants)) are agreed monophyletic, the only issues are the tree connecting them together. I also presume that the whole of those four is also monophyletic, i.e. the tree from the LCA of those four doesn't include anything else currently-living.

So that WikiPedia page you referred me to seems to prefer the tree: ((Anthocerotophyta (hornworts) + tracheophytes (vascular plants)) + (Marchantiophyta (liverworts) + allOtherLandPlants) but in this context allOtherLandPlants would seem to include only the mosses; if so, then OpenTreeOfLife is in agreement with the WikiPedia page.

Am I missing something here? 198.144.192.45 (talk) 01:21, 19 October 2015 (UTC) Twitter.Com/CalRobert (Robert Maas)

The only other point is that there are extinct plants which aren't tracheophytes, so a strictly correct statement is, as far as I know, that embryophytes (land plants) are considered to be a monophyletic group, composed of four monophyletic groups, liverworts, mosses, hornworts and polysporangiophytes. All the living polysporangiophytes are tracheophytes, also considered to be a monophyletic group. Peter coxhead (talk) 08:16, 19 October 2015 (UTC)

Requested move 5 December 2015

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: not moved. As Peter says, we generally only go with parenthetical disambiguation when natural disambiguation is untenable. Redirects can be taken to WP:RFD, but my guess is it would be kept per WP:CHEAP. Jenks24 (talk) 13:01, 14 December 2015 (UTC)

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Evolutionary grade → Grade(Taxonomy) – this can be more easily found. this is more catchy name . Ankit2299 (talk) 18:56, 5 December 2015 (UTC)

• Oppose Parenthetical disambiguation is usually only used when natural disambiguation fails, which it doesn't here. I doubt anyone would search for "Grade (taxonomy)". Grade is probably how people will find this article. Peter coxhead (talk) 19:35, 5 December 2015 (UTC)

  I made a redirect for the page, since there is no harm in extra redirects, Sadads (talk) 22:30, 7 December 2015 (UTC)

  Apart from the fact that it's a poor redirect for three reasons: (a) nobody will be searching for "Grade (taxonomy)", (b) there should be a space in it, and (c) taxonomy should be lower case. -- Necrothesp (talk) 13:57, 9 December 2015 (UTC)

  In fact the redirect Grade (taxonomy) already exists, so Grade(Taxonomy) should be deleted. Peter coxhead (talk) 16:45, 9 December 2015 (UTC)

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The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

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