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Posted by WW on March 01, 2003 at 01:46:42:
In Reply to: WW, thnx....& a bit more.... posted by regalringneck on February 28, 2003 at 21:23:10:
Thanks for that..
:RxR: Well I'll be happy to share a drink w/you in any case! But your example re: uniformity of subspp. to a steep cline is what I observe in the viridis rattlesnakes, and getulus kingsnakes here in Az where they intergrade???
Well... there are plenty of people now who would call these separate species, at least in the case of C. viridis. Ashton & de Queiroz suggested two species should be recognised, Douglas et al. recognise seven. See http://biology.bangor.ac.uk/~bss166/update.htm for a summary and references. Personally, since my student Catharine Pook and I have worked on these and have data beyond mtDNA, I would not support the more extreme views on this, but even so, just because they have traiditonally been viewed as a single species does not mean that this is fixed in concrete.
:RxR: I guess what I'd like to hear is your definition of a species...
:WW: An independently evolving lineage. The major question, of course, is defining "independently evolving" and what evidence is required to fulfill that criterion.
:RxR: Im old fashioned & like the "reproductively isolated" criteria & ideally some niche differentiation to boot.
I guess I just don't adhere to the single criterion "reproductive isolation" as the one and only marker of species status. Moreover, for allopatric forms, it's untestable. There are plenty of taxa that act as good species in the wild and yet turn out to be reproductively compatible under artificial conditions.
:WW: Personally, when I see two "forms" such as melanurus and corais, which are morphologically +/- invariant over vast ranges, consistently distinct, and sympatric in N Venezuela, and approaching a third, equally distinctive form, then to me, the most parsimonious interpretation is that they are 3 species. After all, what evidence is there that they are NOT separate species? Sure, it's a hypothesis that should be tested, but with the evidence available at the moment, the multiple species hypothesis seems the most parsimonious interpretation.
:RxR: I was unaware of the sympatry in Venezuela, this more than anything else requires me to accept your thesis that they are "good spps".
Check the distribution map in the .pdf of my paper (available from my site): both melanurus and corais occur in and around the Cordillera de la Costa in northern Venezuela. Moreover, they do show habitat differences: D. melanurus occurs in higher moutains, primarily in mesic habitats, whereas D. corais occurs in hotter lowlands.
: Your DNA work will be most interesting. Meanwhile if one of the lads here would just cross melanurus & corais, we might create the pattern of that most unattractive guardian...caudomaculatus!
Not sure - I doubt you would get the isolated cream or dark scales, or the mottled throat. You are right about the attarctiveness of caudomaculatus, I am pretty sure we would not have a Drymarchon forum here if they all looked like that one! ;-)
: Lastly for now...I submit if the morphometric characters you have chosen & measured occur as a range in larger sample sizes...the most parsimonious interpretation is for your beast to be an intergrade.
No! Check the PCA ordination plot on the side: D. caudomaculatus is not in any way intermediate between D. corais and D. melanurus. If anything, D. corais is intermediate between D. melanurus and D. corais.
In terms of mtDNA sequence, D. caudomaculatus differs by ~ 9% in cytb sequence from D. melanurus - those two are the ones I happen to have samples of. Obviously, if the good people on this forum were willing to provide small tissue samples or blood of the other species, then that would help considerably... hint, hint!
> Also be aware some pretty odd looking cribos have shown up here before, purportedly from Peru, one of the organized waifs of this forum probably archived those jpgs...
So did I ;-) I do lurk here from time to time. That Peru critter looks pretty amazing, but is almost certainly a colour variant of D. melanurus, occupying the extreme south of the range of the species in extreme NW Peru, near the Ecuadorian border.
:WW: I am hoping to do a DNA follow-up, as well as a more comprehensive morphological study of the entire genus one of these days, but at the moment, I don't have samples for enough taxa. Too many snakes, too little time, to quote Rick Shine.
:WW: Just a few thoughts... Cheers, Wolfgang
:RxR: Please keep us in mind as others come to you, I wish you would spend more time here & less on that %#@-elapid forum :)
Sorry John - the main thread of my life is "no fangs - no fun" - Drymarchon are honorary cobras as far as I am concerned ;-)
:One day I hope you'll share what you learned about Clelia whilst prowling the tierras del sur...
Not a huge amount, except for the fact that they, like other Pseudoboines (Pseudoboa, Oxyrhopus, Drepanoides, Phimophis) are pretty unique in *always* racing across roads at night, as opposed to crossing slowly, like other snakes.
Catching a 198 cm specimen in Belize was a highpoint of my field herping career. Having to explain it to the hotel manager after a chambermaid stumbled upon it in my room was one of the low points... until the manager grinned broadly and said that this sort of thing ought to happen more often to keep the staff on their toes. Ah, the joys of tropical herping...