Reptile & Amphibian Forums

Re: "rule of thumb" in the previous thread. How much stock is put in the alterna/rock rattler/pictigaster mimic idea? Just seems like natural selection wouldn't put much pressure in selecting for color pattern for a snake which spends so much time underground, and out on moonless nights.
-----
Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet

why not???....alterna are also out on mooned nights......predators also hunt on moonless nights.....

Also, color vision isn't needed at night so the pattern tends to look even more similar. Add Trimorphs to the mix too.
Best...
Jim

Compare monochromatic (black and white) photos of each species and then you'll get the picture (no pun). That will be the visual image most mammalian predators see. Color images are what avian predators see. Once you make the comparison it will make perfect sense to you. The snake's color pattern has evolved to deal with both groups of predatory organisms. Don't forget that substrate particle size plays a role in selection pressure for pattern in L. alterna as well.

The mimicry hypothesis makes one strong assumption: that the venemous species color/patterns determine those seen on alterna (and Trimporphodon). However, it does NOT explain why the venemous species (i.e. lepidus and piktigaster) have the patterns they do nor the range of variation they exhibit (of course the color patterns on them can be readily argued to be a function of camoulflaging). I personally do think there's something to the argument but also wonder whether a significant component of the equation has to do with two other hypotheses: The first is that there are certain adaptive patterns that are effective for camoulflaging and that alterna and trimorphs have independantly hit on the same formula as lepidus and to a lesser extent, pictigaster. An old hypothesis (at least for the blairi morphs) may also apply: flicker fusion. Everyone probably knows this one but basically its the optical illusion created with movement of a sharply banded snake that leads one to grab (as a predator or collector) where the animal was instead of where it is. That explanation does not work for speckly alternas but then they are nowhere near as common as banded ones. The brighter the color, the better the effect of flicker fusion, which could explain the fourescent colors seen in some alterna and of course many of the tricolors.

If you put these hypotheses together, they work fairly well: effective camoulflaging, mimicry so a predator is deterred, and flicker fusion so the predator misses if they are not deterred. Just wait till they evolve counter-collecting defenses! Come to think of it, they may have already done so for some collectors who have not had much luck...(its a great excuse). --Henry W.

I did a project in college to explore the issue as I was intrigued by some of what I saw with regard to the overlap of similarly patterned critters (venomous and non-venomous). While at the time I had a rather romantic view of the kinds of processes that would have to have taken place in order to make a mimicry scenario feasible, my investigation (albeit a rather elementary one) seemed to point towards the simplest and most likely answer... that the fantastic patterns and colors of gray-banded kingsnakes, lyre snakes, rock rattlesnakes, and copperheads were the result of a convergent evolution for successful patterns. I can't recall some of the specifics off-hand, but that was the gist of the finding. I'll see if I can't dig up some of my old reports and graphical representations of pattern similarity/overlaps and some of the reasons that I felt mimicry was probably more unlikely than I initially thought.

While at the time I had a rather romantic view of the kinds of processes that would have to have taken place in order to make a mimicry scenario feasible,

That's what I'm thinking too--a lot of the opinions on mimicry have been relatively unchallenged for decades, especially the alleged coral snake mimics, of which many have a far greater range than the coral snakes do!

I think the convergent adaptation scenario makes a lot more sense.
-----
Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet

I did a similar research paper in college myself . . . I came up with "convergent crypsis secondarily reinforced by mimicry". Of course, I wasn't the first to coin that notion by a long shot. LOL

Troy

The whole mimicry idea was a pretty disappointing once I did some research. I'd built it up in my mind as such a revolutionary portion of evolutionary theory just to find out there's no real way to test for or prove its existence. I feel comfortable with the idea that it applies as a minimal-impact secondary pressure, but the theory, just by its nature is such soft science... theoretical at best and practically impossible to empirically test for. On the surface it appears to explain some observations, but there are other ideas that are just as plausible and would require less effort on the part of nature. The simplest idea often proves to be the correct one. It is a lot of fun to think about though. It's funny we both did research on the same thing... I guess we know where our minds were wandering during class. LOL