Thanks, you 2, for a great comment and response..N/P

Subject:

Comments:
: : : W/o giving us the criteria by which your 17 distinguishing parameters were selected; ie why not head scalation/tail length ratio/ etc. : : The characters were chosen on the basis of preliminary observations suggesting that they showed significant variation between corais, melanurus and caudomaculatus. : : The characters used were: : : 1. Ventrals : : 2. Subcaudals : : 3. Anterior temporals : : 4. Contact upper anterior temporal - posterior temporal(s) (0 = none, 0.5 = one side, 1 = both sides) : : 5. Posterior temporals : : 6. %VS position of reduction 19 to 17 rows : : 7. %VS position of reduction 17 to 15 rows : : 8. %CS position of reduction 10 to 8 rows : : 9. %CS position of reduction 8 to 6 rows : : 10. %CS position of reduction 6 to 4 rows : : 11. Change of colour along dorsum (1 = darker at front, 0 = uniform, -1 darker at back) : : 12. Oblique black mark on side of neck (1 = present, 0 = absent) : : 13. Presence of individual paler scales (1 = present, 0 = absent) : : 14. Change of colour along ventral side (1 = darker at front, 0 = uniform, -1 darker at back) : : 15. Underside of tail pale or dark (1 = dark, 0 = pale) : : 16. Presence of individual dark subcaudals (1 = present, 0 = absent) : : 17. Presence of obvious dark edges on supralabials : : : While no systematist myself, & an admitted lumper...I would think in this day of DNA (though please note: some arbitrary criteria in this "wonder technology" is employed there; deciding which markers are meaningful) to make this claim, one today needs to complete this analysis. I note from you list of publications, you have considerable experience in this regard. I presume the DNA analysis is still a work in progress? : : DNA is not the be-all and end-all of systematics. If you look at the journals, a very large number of reptile species are still being described without recourse to molecular markers, simply because they are often not needed. In this case, the blindingly obvious qualitative pattern differences, and quantitative scalation differences, provide more than enough evidence to show caudomaculatus to be a new species and corais and melanurus to be separate species. The two species do approach each other very closely in N. Venezuela, and show clear ecological segregation. You don't need DNA to tell you that these are separate species. I am slowly accumulating samples, and hope that one day I will have enough to do a Drymarchon phylogeny. However, bear in mind that this project was very much a sideline - I happened on the new species while working on Bothrops and Crotalus, and felt that it needed description. I retain an interest in Drymarchon, but only as one of (far too many!) side projects. : : : A clade chart depicting Drymarchon as well as the guardians within Colubridae ought to be bundled in this type of paper. : : Depends what the paper is supposed to achieve. The main aim of this paper was simply to describe the new species. You don't need a cladogram to show that a species is distinct. The only reason why we went on to reclassify the remainder of the genus is that we did not want to leave the nomenclature in limbo - since all Drymarchon were previously believed to be ssp. of the S. American D. corais, but are clearly not conspecific with it, we had no choice but to address this. Throughout the paper, we have emphasised that this was a purely provisional arrangement and that more studies are required (as an aside, I find it quite amazing that nobody has done more work on Drymarchon before!). A phylogeny of Drymarhcon, preferably molecular, would certainly be a very nice addition. : : : For me, I like to see an ecological/behavioral aspect to speciation. If there are not definitive barriers to recent gene flow, such as Fla. to Texas, Cuba to S. America, theres no reason not to presume a cline in a monotypic genus. : : There is ecological separation between D. melanurus and D. corais in northern Venezuela - D. melanurus occupies higher elevations in the northern Cordilleras, whereas D. corais occurs in the lowlands. We have looked at specimens from localities within a few 10s of km of each other, and there is absolutely no evidence of intergradation. If there are occasional hybrids or hybrid zones, then they are very narrow indeed, and do not, in my view, preclude these taxa from being considered as separate species. : : The whole thing relates to the question of species concepts. I am pretty skeptical of the biological species concept, certainly if one applies it rigorously at the first sign of a hybrid. Even if there is a 10 km wide hybrid zone bewteen melanurus and corais along the foothills of the Venezuelan Cordilleras, so what? These two forms are morphologically homogeneous over 1000s of km, so does a slightly fuzzy edge really stop them from being to all intents and purposes evolutionarily independent lineages? I would answer that with a strong negative. : : In any case, I disagree that we should presume there to be a cline unless proven otherwise. In the presence of clear, categorical differences between two forms, it strikes me as more parsimonious to assume that they are entirely separate than to assume that they are not. Maybe I am just more of a splitter at heart... (although one of my last papers actually lumped two species!) : : : I do agree that erebennus appears to be a melanistic cribo, & have noted the cribo neck markings are sometimes apparent on them. I assume the Eastern indigo neonates & yellowtail cribos do not have these neck bars??? : : I have not seen them in any of the material of juveniles that I have examined. The juvenile pattern of D. caudomaculatus is unknown, I am not aware of any juvvies having been found. : : : It would be interesting to know if the guardians on their far S. distribution (Argentina?) also tend towards melanism? : : They don't. : : : I'm not there yet for 5 reproductively isolated guardians, but Im open minded & enthusiastic that you & your colleagues are examining them. : : Reproductive isolation, as I said, is very much a matter of what species concept you apply. D. margaritae and D. couperi are geographically isolated and differ consistently from the other species - whether or not they can hybridise in captivity is pretty irrelevant. D. melanurus, D. corais and C. caudomaculatus occur in close proximity, and show no sign of intergradation. Even if they are not entirely isolated, they are certainly independently evolving lineages. As to the remainder, I have taken the conservative view that reports of intergrades in the literature suggest that they may be conspecific. However, I rather expect that, once these get revised thoroughly, we will find that there are in fact more separate species than we are recognising now, not fewer. : : : Again thankyou for taking the time to share your work w/ us. I have appended your text below. Curious homonids desiring to see more of WW's considerable work should load the following URL; http://sbsweb.bangor.ac.uk/~bss166/ : : Thanks for your comments! It's the sort of thing that helps keep one sharp. : : Cheers, : : Wolfgang

Optional Link URL:
Link Title:
Optional Image URL: