`Not so. Elaphe scalaris, which is one of the species analyzed by Lopez and Maxson is considered a member of the monotypic "Rhinechis" by Utiger et al.'



Ah yeah, I'd forgotten that they included Rhinechis. Rhinechis'd already been split off before Utiger et al.'s study, though, and, given the large amounts of both morphological and genetic disparity involved, I don't think there's much reason to doubt that the split was warranted. And, since some of that morphological disparity is in nice and obvious features of scalation and head shape, even you should approve. : )



`If several species evolve from a single species so quickly that there is no time for the mtDNA to evolve into more than 1 lineage, then all of the species will have identical ancestral mtDNA markers, with subsequent autapomorphic changes appearing in each descendant species but no common markers to link any species pair more closely to each other than to other species. The result is an unresolved polytomy involving multiple species, such as the kind seen in Rodriguez-Robles et al.'s analysis of the Lampropeltini. Adaptive radiation can result in polytomies. This is something that competent systematists know.'



Ok. I'd guessed that rapid lineage divergence and the resulting `shallow' phylogeny was what you were referring to, but since this isn't inherent in adaptive radiation, and can result from other processes such as sudden range expansion, I wasn't sure.



So, is there any reason to suspect that this is the case in Elaphe sensu lato? I seem to recall Utiger et al. discussing phylogeography at the end of their paper, but don't have the paper with me...



`That is not possible. This is the first time I brought up Tong et al's bootstrap value for this node.'



The bootstrap value isn't the problem. The taxon representation is the problem.



`Tong et al. show that all of the Old World species of Elaphe, including the most basal member, Elaphe mandarina, form a monophyletic group with Ptyas as the outgroup.'



They can't show that, because they didn't study all Old World members of Elaphe sensu lato. Outgroup representation would also need to be much higher for this to be compelling.



`Lopez and Maxson show that all species of New World Elaphe (along with their descendants in the Lampropeltini) form a monophyletic group with the Old World species they study basal to the New World clade. Ptyas is the outgroup.'



Lopez and Maxson don't study all New World species that were in Elaphe at the time of their publication, so they don't demonstrate anything about all of them. Furthermore, all studies of lampropeltinine phylogeny I've seen show Pantherophis to be one of the more derived clades within Lampropeltini. Though lacking sufficient taxa to provide good support for this, Lopez and Maxson's results are also consistent with a derived status for Pantherophis within Lampropeltini.



It's also worth mentioning that Ptyas is not the taxon most closely related to Elaphe sensu lato in Lopez and Maxson's study, so is not `the' outgroup.



`That is not possible. Their data shows that New World members of Elaphe are all part of a monophyletic group they call "Elaphini." As I said, they have a hunch that Old World Elaphe and New World Elaphe may form a polyphyletic group, but they have no data to show one way or another. Utiger et al., nevertheless, cites this paper for evidence that some authors have concluded that Elaphe is polyphyletic. Dowling et al. are merely speculating about this possibility since their data cannot answer that question one way or the other.'



Ok.



Did Dowling et al. conclude that Elaphe sensu lato is polyphyletic, BTW? I ask because, if they did, then whether or not this conclusion was speculative is irrelevant to their having been cited as having concluded that Elaphe sensu lato is polyphyletic--your wording above suggests that you think Utiger et al. cite him for this erroneously, and I'm curious as to whether or not this is the case.



`If any author had convincingly demonstrated that Elaphe is polyphyletic, it would not have survived the past decade and a half intact. It is quite obvious that Dessauer et al. are speculating based on that fact alone.'



There's a large gulf between `convincingly demonstrated' and `speculated'. My guess is that Dessauer et al. fall into this gulf.



`I might not have read it, but Tong et al. did. I have since read it, and there is nothing in there that shows Elaphe is polyphyletic. Dessauer et al. find that Elaphe quatorlineata is basal to New World Elaphe and the Lampropeltine species.`



Which paper are you referring to, here? I'm guessing you're referring to the 1987 paper. As per my corrective post, the 1983 paper was what I was referring to.



`That is consistent with the results from the newer papers that refute Elaphe polyphyly.'



I do wish you'd quit begging the question like that...



`I do not remember any such paper. Please refresh my memory.'



See the link.



`They would have dismantled Elaphe if they had proof that it is polyphyletic. Absolutely! They have no proof that Elaphe is polyphyletic. That is why they do not dismantle it. Nothing wrong with my argument, especially since I have shown that Dowling et al. and Dessauer have no data to prove that Elaphe is polyphyletic. I still haven't read Minton but I am confident that he has no data to show that either.'



I suggest you re-read what I wrote. Note that I was phrasing this in terms of

belief rather than proof. There's a pretty wide gulf between the two, and I put it in those terms because that's what I thought was implied in your post. AFAIK, it is the case that Dessauer, Minton, and Dowling believed that Elaphe sensu lato is polyphetic. They didn't dismantle the genus, however. My guess is that they thought that a revision of the genus should await more comprehensive and definitive studies.



I said:

`Apart from that, a taxon's long-term recognition is very poor evidence of mono- or paraphyly.'



You said:

`Do you have any evidence that a polyphyletic taxon, any polyphyletic taxon, has continued to be recognized despite its polyphyletic status?'



Many taxa now known to be polyphyletic have been recognized. A couple examples that come to mind are Natrix, when it included Nerodia, and Coluber. The problems of Coluber still haven't been comprehensively addressed, though Schatti and Utiger (Revue Suisse de Zoologie, 2001; 108 (4): 919-948) have begun to sort it out.



`True. But a lineage that is basal to another can indeed be ancestral to it.'



If two groups form sister taxa (as you say Elaphe quatuorlineata and Lampropeltini do in Dessauer et al. (1987)), one by definition cannot be ancestral to the other. So, according to this phylogeny, Elaphe quatuorlineata cannot be ancestral to Lampropeltini.



`If New World Elaphe and E. quatorlineata share a recent common ancestor, then there are two possibilities. Their common ancestor is a species of Elaphe or they are only convergently similar, meaning that their common ancestor is not like Elaphe and that the New World species of Elaphe are only convergently similar to E. quatorlineata. The second alternative is certainly possible, but not as parsimonious.'



That is incorrect. If we take Lampropeltini and Elaphe quatuorlineata to form a monophyletic clade, then if Pantherophis and Elaphe quatuorlineata share similarities not found in a common ancestor, their similarities evolved once in an ancestor of Pantherophis and once in an ancestor of Elaphe quatuorlineata. Because Pantherophis is a derived taxon within Lampropeltini, if Pantherophis and Elaphe quatuorlineata share similarities present in a common ancestor their similarities arose once in a common ancestor, were lost in an ancestor to Lampropeltini, and arose again in an ancestor to Pantherophis. So you've got two state changes vs. three.



`Most systematists would agree that New World Elaphe is descended from an Old World species of Elaphe. Most systematists would agree that Elaphe is not polyphyletic.'



Have you asked them?



Patrick Alexander
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