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Date: Mon, 14 Jun 2004 14:35:37 +0200
From: cej@gli.cas.cz
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: RE: LITU, and lineage names
Hi, folks, i post a short debate with Fredrik Pleijel [hi, Fredrik!], to know where = *you* stand... >> I would vote for your LITU's: at long last, a clean concept appeared! = >> We paleobiologists (paleontologists, if you wish) face another = problem:=20 >> we got used to consider "species" being parts of phylogenetic = lineages=20 >> between two apomorphies -- and we need names for them. These are not = clades,=20 >> unlike LITU's, so what we should do? Although extant "species" can = sure be=20 >> transformed into clades, non-terminal extinct ones can not.=20 >> Just as clades are defined by single nodes, these "chronospecies" are = >> the internodia, or their parts. Yes, and we need names to refer to = them=20 >> (and there is to be much more these "chronospecies" than = nodes=3Dclades=20 >> (actually as many as independent apomorphies recognized)). >> Litu has no sense when you include time within the play:=20 >> what is LITU today will become a clade tomorrow (read: after = radiation event(s)). > I would say LITUs certainly make sense when you include time (after=20 > all, we are historicians). A LITU does not make any absolute=20 > statement=20 > about the group being indivsible, it only states that it's=20 > the smallest=20 > (least inclusive) group that we have recognised at present (whether=20 > recent or extinct). The moment someone subdivides it, it=20 > ceases to be a=20 > LITU. however, it is not the entity I would like to refer to: I need to = *exclude* all its decsent that differs! > As for the species problem in palaeontology, I think it's just a=20 > special case of a much larger one, namely identifying paraphyletic=20 > groups.=20 If I got it right: yes, "species" is, by definition(s ;-), a = paraphyletic group of individuals as it can evolve into other "species" > I just don't think we should recognise them as taxa, and that=20 > for a number of reasons, possibly the most important being that we=20 > don't know what we're naming - 1 lineage, or 100 different lineages,=20 > only united by their lack of diagnostic features? That is the problem=20 > one runs into in the case you mention with "species" being parts of=20 > phylogenetic lineages between two apomorphies. My view is that we=20 > should know something about the things we label... And when we think=20 > about it, how important is it to name all of these 'things" that we=20 > don't know much about in terms of lineages? What do they permit to=20 > conclude?=20 usually, only that entity1 differs from entity2 :-( but, isn't it enough = for a name? surely we should *not* mix these entities (whatever they are called) = with clades, and perhaps we should *not* include them (recall: speaking about = "species") within the phylocode. then, however, I would vote for a "Nomenclature for Species", making = these two independent, for the sake of clarity -- of course biologists should refer to them = both, but I am against expressing (hypothesized) clade membership within the "species" names -- = put the connections to the database. Thus, we can have, e.g.: merula (Aves: Turdus)=20 as a name and hypothesized relationship, as it can appear in papers... or something alike. > For the rare cases when it really is important to relate to=20 > them, then I would just use an informal name. But I guess I'm in=20 > minority... Love to know your opinion(s), regards, Peter. Peter A. Cejchan Lab of Paleobiology and Paleoecology Prague, EU http://www.gli.cas.cz/home/cejchan =20