Talk:Polyphyly

message: This is a nice image, but I don't think it actually describes a polyphyletic group.  The common ancestor of amphibians and mammals was a land vertebrate, and although the illustration does not show this, the lower land vertebrates are usually meant to include it.  As such, this is a paraphyletic group, comprising all its descendants except the mammals (and I would think the birds).  Might a better illustration might be the warm-blooded animals, highlighting Mammalia and Aves separately? Josh
Well, are you sure that the warm-blooded animals are a polyphyletic group? Was the most recent common ancestor of birds and mammals warm-blooded or cold-blooded? I think this picture actually shows a paraphyletic group, doesn't it? Because the yellow curve includes the fork between Mammaila and Aves? I don't know, I'm no biologist. Keenan Pepper 19:50, 21 July 2005 (UTC)
replies: text: New image, based on the discussion here. There is also an svg source for the image on commons, so it should be very easy to correct. Zeimusu | Talk page 15:40, 30 September 2005 (UTC)
thread_title: [[:Image:Polyphyletic.png]]

message: Please see Talk:Monophyly#Why_have_three_articles where I have asked why there should be separate articles on monophyly, paraphyly and polyphyly. Please leave comments there. Peter coxhead (talk) 15:57, 6 December 2010 (UTC)
thread_title:  Why have three articles? 

message: Wikipedia currently provides two explanations of the near-universal rejection of polyphyletic groups. In both cases, the contrast is with monophyletic groups. In the article Polyphyly, it is noted that:
::Because polyphyletic groups can frequently be defined as a sum of clades, some consider them less fundamental than monophyletic (single, whole) clades.
Also, Phylogenetic nomenclature#Philosophy cites Hennig:
As to the first reason, the fact that polyphyly is "less fundamental" than monophyly is an inadequate reason for the widespread rejection of polyphyletic groups in most areas of biology.  In this sense, monophyly is less fundamental than ancestry (monophyly is defined in terms of ancestry), but there is no parallel rejection of monophyly. As to the second reason, I am not aware of a widespread conviction among biologists that anything  must have "an independent history", whatever that is. Finally, any force these arguments have against polyphyly tells also against paraphyly. Many biologists are quite willing to accept well-supported paraphyletic groups but few would countenance polyphyletic groups as formal taxa.
I have my own ideas as to why polyphyletic groups are so totally unacceptable while paraphyletic groups are often thought useful.  To expound them, however, would be OR. Is there any discussion in the literature as to why polyphyletic groups are such a bad idea? Peter Brown (talk) 22:34, 30 July 2013 (UTC)
replies: text: As we've found before, finding modern sources which discuss these concepts isn't easy! You have to go back to the purposes of classification and then ask whether polyphyletic groups meet them. My problem in finding sources for this is that many of them are highly polemical and primarily interested in attacking each other; they generally don't discuss areas of agreement at all.  has a nice discussion which I think is relevant, although not specifically put in terms of polyphyly. It's to do with predictability. Linnaeus' Diandria (plants with 2 stamens) is a polyphyletic group. Knowing that a plant belongs to the Diandra doesn't allow you to predict anything much else about the plant: grasses, speedwells and slipper orchids are in this group. Having 2 stamens is simply a convergence. On the other hand, if you know that a plant is in Araceae sensu Stace (which is paraphyletic because it excludes Lemnaceae) it allows you to make many predictions; e.g. that the inflorescence will consist of a spathe and spadix. His Araceae possess these characters through shared inheritance, not through convergence. Peter coxhead (talk) 07:20, 31 July 2013 (UTC)
replies: text: Thanks! Just what was needed. Peter Brown (talk) 18:22, 31 July 2013 (UTC)
replies: text: I really like the way you've worded the addition. There's much more along these lines by Mayr, but he's too polemical, I think. Peter coxhead (talk) 18:26, 31 July 2013 (UTC)
thread_title:  What's wrong with polyphyly? 

message: What if a taxon had some apomorphies (novel traits) that persisted for a very long time in some lineages, rapidly disappeared in others, and persisted for a moderate amount of time in yet others. For example, labyrinthodonts. They inherited a suite of 5 traits from their tetrapodomorph fish ancestors, along with a 6th (relating to the skull table) from a basal tetrapod. These traits persisted for tens of millions of years in those lineages that remained bigger than a breadbox. In those lineages where size dropped to below the size of a breadbox, the halflife of the traits was inversely proportional to the size of the animals. The result is like a starburst pattern, with a single starting point (the first tetrapod) but many ending points. I don't think it even counts as an evolutionary grade. Ripidista (by the old definition) had a similar problem. Zyxwv99 (talk) 22:49, 14 June 2015 (UTC)
replies: text: Never mind, I found it. It's polyparaphyletic. Zyxwv99 (talk) 22:53, 14 June 2015 (UTC)
thread_title:  Is there are fourth category besides monophyly, paraphyly, and polyphyly? 

message: The following source was once in the article but is no longer cited as of the current version:
* 
 — SMcCandlish ☏ ¢ 😼  21:16, 10 September 2023 (UTC)
thread_title:  Additional sources