When I published my first article involving phylogenies, the editor waited until the last round of corrections to suggest that I should abolish the word "basal" in my text. In fact, whenever an OTU was the sister of another, I used the term for the OTU sister. He then explained that the word refers to the basal node that gave rise to the current OTUs, not the sister group chosen for analysis. I always thought this makes sense, however, whenever I read articles or watch lectures on phylogeny, I see the word applied to sister groups (in several cases, extant sister groups). I would like to know what the members of Research Gate think about it.
I couldnt understand your point exactly, do you mean asking in your case "which one is real either clade as a category (sister group etc) or individuals ?"...
My point is only the use of the term "basal" to refer to sister groups or OTUs.
The point is that "basal"should refer to ancestral organism and not current organisms.
Suggest that a clade (a monophyletic sister group) do not contain an ancestor but current organisms. Howvever, same clade do contain ancestor because it is basal at the same time (a big problem of cladistics). Conclusion, basal ancestor is a contradiction.
The editor was right, basal implies primitivity...while a sister group (even if composed by a single species) is not necessarily more primitive respect to the other one. Hence, it is better to use the terms "early branching". I suggest you to read the very interesting paper of Crisp & Cook "Do early branching lineages signify ancestral traits?" published in Trends in Ecology and Evolution 20(3): 122-128 (2005)
Editor is right, but problem is still hanging in terminology, at least to me. You said "sister group (even if composed by a single species) is not necessarily more primitive respect to the other one", however, they must also be basal to bifurcate into another branch. Moreover, they are extant and real in front of eyes. thank you about the paper you suggested...
only the common ancestor (i.e. the taxon before the node) is actually basal and primitive. It is that common ancestor that goes extinct, and then bifurcates...
Have also a look on the artcile of Krell & Cranston (2004) Which side of the tree is more basal? Syst, Ent.
below the link.
Hope that helps...
http://onlinelibrary.wiley.com/doi/10.1111/j.0307-6970.2004.00262.x/abstract
Nice paper dear Koenig...reporting at the end "Argumentation with sister-group relationships is easy and shows relationships much more clearly than declaring one sister group to be basal. The ‘basal position’ within an ingroup always means ‘sister to the remaining taxa’The ‘basal position’ within an ingroup always means ‘sister to the remaining taxa"
The editor suggested me the krell & cranton paper, and convinced me to do not use the term basal to extent organisms.
The editor is right. The term "basal" is often misused in phylogenetic papers. For a phylogenetic tree, if it rooted, being basal means being near the root; if unrooted, being basal means being near the internodes. So for OTU, they are all concurrent, it is impossible to tell which is basal. I think the misuse just comes from our intuition on the spatial position of objects. In space, we often think the objects at the lower part are basal. Many people used this perception in a phylogenetic tree, but it is definitely wrong.
The next question is, Shi, when you see the bad use of the term in a talk, for example, what do you do?
Hi Karla,
I think this kind of misuse is prevalent in community of non-phylogenetics and I guess most people of this conmmunity percieved the term "basal" spatially as refer to the figure of the phylogenetic tree . This should be ok, but if they disccussed something basal in the context of history. It is wrong and we should point out.
I don´t think so... In several good journals as Plos ONe or MPE, it is very common the bad use of the term basal... I try to be optimistic, but it is increasingly harder for me...
'Basal' means at the base, or below something, and is a relative term. But you can apply it to extant taxa. In your case, if you have two sister clades, then any clades that precede them in time (branch off before your sister-clade node) are basal to them. It can be a useful word to use, avoiding more awkward and longer descriptions, just so long as you use it correctly. So, like all words, don't avoid it, just use it correctly if it makes a situation easier to explain.
you maybe read this paper about insect ralated basal phylogenetic: Ashe, J.S. (1994) Evolution of aedeagal paramerres of aleocharine staphylinids (Coleoptera: Staphylinidae: Aleocharinae). The
Canadian Entomologist, 126, 475–491
I agree, basal is a relative term which implies primitivity in comparison to the OTU you discuss. I think an extant taxon can be more basal than another when it is part of the stem group of the dicussed taxon and has fewer apomorphies sepperating it from the LCA of the OTU dicussed and the taxon of the stem group.
But a taxon (of the sister group of the OTU) that retains characters that have changed in the OTU you discuss this taxon is not necessarly a basal taxon. If you have enough upporting data you ca say the respective taxon has primitive features and this would indcate the basal condition.
I think the sister grooup of the OTU is just to close to call it basal. The taxonomic unit labeled basal should be more distant to the OTU.
I disagree with Jens Kosch: an extant taxon cannot be part of the stem group of another taxon, as a stem group is extinct by definition (it contains all the extinct species that are more closely related to the respective crown group than to any other living taxon). For me the term basal is only applicable to a node (e.g. the basal split in taxon XY), or to extinct species.
Trees do imply a time element, at least a relative one. If a particular taxon (clade) connects to the rest of the tree near the most recent common ancestor of all the species, I think it's OK to refer to it as basal; it branches from the tree at a basal position. Perhaps one could also refer to it as an early branching taxon? I realize that this terminology isn't ideal, but you want some way to refer to the branching position of taxa in the tree when discussing hypotheses about the evolution of the group. As an aside, this terminology doesn't imply anything about the "primitiveness" of the taxon, which is clearly not a sensible statement because all of the taxa were sampled at the same time and we are not discussing the characters of the taxa, only their phylogeny. Moreover, I realize that this terminology is dependent on the taxon sampling. It's possible (maybe probable) that many taxa on this "basal" branch were not sampled. Any way, my two cents.
Basal: towards the tree root relative to a given tree branch/node. The term 'sister' (groups, taxa) refers to two branches of a tree that are connected to (or arise from) a single node. Both terms make sense only for rooted trees.
Dear colleagues,
Please do not use the term “primitive” to the more ancient taxa or features, since modern taxa, by contrast, may be more primitive as a result of regression, reversion, etc.
Best regards,
Vladimir
Vladimir: I do not agree: the primary meaning of "primitive: is "at earlier stage of development/evolution", so e.g. many parasites may - "as a result of regression, reversion, etc." - be more simply built but not "more primitive"!
Roman Bohdan: This is casuistry. In fact, the interpretation of the primary meaning of term "primitive" can be very diverse. In this case, it is better to use the terms "ancestral" or "generalized".
Vladimir.
Vladimir: Sorry, I do not agree again: "ancestral" means "one of the ancestors" or "[a feature of] an ancestor", what (especially as applied to taxa) is but rarely true for a more primitive ones (Archaeopteryx is not ancestral to pigeon or eagle); while "generalized" means again something totally different ("less specialized" "more widely adapted" or the like), what also is not necessarily characteristic of more primitive organisms (hand of humans is more generalized than that of a gibbon - to say nothing of a horse or frog), but certainly not more primitve!
Of course all this is (as well from my as from your side!) a little "casuistic" hairsplitting, because usually it is evident from the context in which sense the term (either that preferred by you or by me) has been used...
As regards the "basal" (main topic of the present discussion) and "stem" (Eva Bährmann's comment):
1) Basal - as some discutants already clarified - means "close to the root", so the term makes sense only to "non-equivalent" (non-sister) branches: sister-clades (whether of equal taxonomic rank or not, whether equally diverse or not, &c.) are by definition equally "basal", so if the phylogeny was e.g. A{B[C(D,E)]}, then A is basal in relation to B, C, D, E, (D,E) or [C(D,E)], but not to {B[C(D,E)]}.
2) "Stem" vs. "crown" groups are purely formal (based on "accidental" circumstance of being entirely extinct or including one or more survived species) terms, sometimes helping to explain one's conclusion, sometimes just obscuring the discussion, but without true biological significance (Crossopterygii were "stem"-group, in 1930's they suddenly became "crown"-group only because Latimeria was found extant!), so it makes little sense to involve these terms in serious taxonomic or evolutionary considerations!
The term basal could be applied to ramification nearer to the root of phylogenetic tree or it could be represented as initial bifurcation.such bifurcated taxa will never be considered as ancestral forms.Such a cluster in any form of tree without a out group is imminent for automated computation to satisfy the statistical or arthematical values to build the tree.
as I understand from article reading, basal term typically use for an individual or group of taxon which related to the earliest branch of a tree.
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