Im new here...but would like to add something of what I feel is a good point for this particular debate.
I would consider myself a amateur herpetologist, but my field is mainly boa constrictors...and looking at these I feel would be of SIGNIFICANT value to those interested.
I believe that creatures of all kinds form mutations of the genes during every successive generation...and over an amount of time...those genes may become so different that they would indeed be considered different species. For instance...stingray being related or descended from sharks. These are obviously at this point 2 different animals, biologically, and would not reproduce a "hybrid" if they somehow mated. Apes to Humans could be considered the same...but I will leave that alone.
But onto the matter I wanted to add...the boa constrictor can be found all over Central and South America...and the islands of Central America. By these I mean the boas classified as BC(x) (boa constrictor...x being the individual subspecies).
In this case, I personally believe that the boas of each region developed a particular look and behavior about them that helped in the survival of those areas they inhabit, while still being technically the same species.
I will not list them all, but key differences are as follows.
The boas found in the southern regions of S. America, and in this case I will point out the Argentine Boa...or BCO (boa constrictor occidentalis) have to withstand temperatures of the region...winters being very cold there. How does a boa succeed in survival in this area? Develop darker colors (thereby absorbing more heat) and being girthier (wider...in this case...helpful in having more body area exposed to sunlight...also helping to heat the snake). The BCO are dark brown to black for the most part as adults.
http://i137.photobucket.com/...tic25/800px-Argentine_Boa.jpg
Further to the North we see several species...but will point out a few. The BCC (boa constrictor constrictor) is the largest of the BC, and inhabits many areas...with subtle changes in looks and length of the animals. Quite beautiful...but biologically, what helps them to survive in their areas? Generally, u can find these in Brazil, Guyana, Peru, Venuzuela, among other insular varieties found in smaller parts of said countries. These boas are very thin bodied looking down at them from above...but on closer inspection, u find that their body shape is rectangular...they are much taller than they are wide...not a round body like u would think a snake should have. How does this help? I would venture a guess that it allows for more surface area vertically, which would aid in doing what boas do best...constrict around their prey. It would allow the snake to be more adept at catching...and killing...larger animals than other boas. But once again, this is my own speculation.
http://i137.photobucket.com/...s/q212/Franatic25/99male2.jpg
Other boa subspecies exist, but will only point out one other...because it is the most interesting...biologically speaking...to me. BCI (boa constrictor imperator) inhabits the greatest area, and is the most successful subspecies. In fact, there are several BCI that have entirely different looks to them, but are considered the SAME subspecies simply because of how close the individual locales are to each other. Columbian BCI being the common boa you will see at petstores. Very large, girthy, animals. But lets consider them the "control" of the BCI.
Going further north, into Central America...we see nothing but BCI...but their differences are distinct. Boa's that inhabit the mainlands of Central America...El Salvador, Nicaragua, Honduras, are all very similar...but smaller than their columbian brothers. But it gets VERY interesting when you consider the Islands varieties of BCI. Here we see survival of the fittest at its best.
The small island (now islands...separated into 2 parts by Hurricane Haittie) of Caulkers Cay isone of the smallest of all BC locales (Tarahumaran Mexican boas being the smallest, but I will leave them alone for now). Their variety being the Caulkers Cay boa (considered BCI). What u will see on Island boas is 2 things...they are smaller than their mainland brothers...but also because of the small population...these boas ALL have their own distinct looks, probably due to the few boas that were on the islands when they seperated from the mainland...or another theory is they drifted their from debris from Belize several thousand years ago. In any case, the point is that since the genetic pool is much smaller, the boas tend to develop differences in color, size, more quickly, by way of the better part of the boa population having a particular gene for size, or color, pattern, etc.
In the case of Caulker's Cay...the boas found there are very nearly all anerythristic (lacking color pigment). They also must avoid the crab population during the turning of the tides...so they are also one of the leanest and arboreal (able to climb trees) of the BC. Less prey on the island (only 5 miles x 1 mile) made the success of the smaller boas more apparent. They thrived on less sustanance, and therefore passed the genes for "small" boas onto their offspring.
http://i137.photobucket.com/...q212/Franatic25/Caymale-1.jpg
On the polar end of what u would expect...are the boas of the "Cayos de los Cochinos", or the hog isle boa, also a BCI. These could not be more different. What they have in common with other island boas and the Caulker's Cay boa is size...they are smaller than mainland boas. But the boas that ended up on this island untold time ago, came from Honduras most likely since it is roughly 10 miles from the coast. The slight difference...and the boas on said island that reproduced...passed on interesting traits. They are more naturally hypomelanistic (lacking black color pigment). Now keep in mind that anerythristic and hypomelanistic boas Do occure in other locales...but they are morphs...much like an albino. Whereas the boas of Caulker's Cay and the Hog Isles are NOT morphs...nor do they carry the gene that causes the morph. They simply have a collection of other genes (theoretically) that cause them to look the way they do. In this case, I would venture that the lighter color acts as a way of NOT taking in as much heat as the BCO mentioned earlier. They would instead reflect some of it, like wearing white clothes rather than black. They also have very pronounced color "phases". Being much darker during inactive hours, and brighter when active. The cause of this can be debated...I dont know the reason...but this is a common trait in THIS ONE subspecies (other boas can have phases....but not to the extend I am speaking of with this subspecies)
http://i137.photobucket.com/.../q212/Franatic25/DSC00076.jpg
So the question is, how do we interpret this information? It cant be disputed that a difference in appearance, among other things controlled by genes, doesnt happen elsewhere. Take the domestic dog...we have several "breeds", but any dog has the potential to produce offspring with any other dog because they are the same species, just having different genetic code causing (in this case, selective bred by people) them to look different.
These boas are like this for much the same reason I feel. Any of the boas Ive mentioned could produce offspring with any other and produce a "hybrid". On the genetic level, they are essentially the same animal.
Now going further back in time though, we can see other boas that could NOT potentially breed with a BC...they have separated genetically enough. A good example...the Dumeril's boa of Madagascar...
Once upon a time the lands of S. America, Africa, and hence (maybe) Madagascar were linked. These boas have had a longer period of time in isolation from there cousins in the americas. The differences being an obvious shift in pattern...BC have "saddles", and spears or cross patterns on the head, and tails of differing color from the body. Not the case in Dumeril's...their tails have the same color and pattern as the rest of the body, and the pattern is quite wild...beautiful. They also have much slower metabolisms, needing roughly half the intake of food as the BC, which in turn causes them to grow slower and reach sexual maturity later (BC being roughly 3 years, Dumeril's roughly 5).
http://i137.photobucket.com/.../q212/Franatic25/DSC00012.jpg
Other species of boa exist in the SAME locale as the BC boas...but are also not compatible. Everyone knows what an Anaconda is...it is a boa, but not directly related to BC...and Anacondas can get roughly 20 feet...BC's largest subspecies being 8-9 feet, but larger ones do occur...but nothing nearly the size of an anaconda.
Tree boas occur as well. Boas that live their whole lives in trees, and are very adept at climbing, and are much more vividly colored...the largest tree boas subspecies being the Emerald Tree Boa...which is green...u can figure out why. Once again we see that the boas with the better genes for the job passed them on as a direct result of their success.
Going further back, u might want to say that all snakes came from a single species...which may be. But Im not so sure. One of the BIG things that makes a boa a boa...is the fact that they have 2 lungs....other snakes (besides pythons, which have similarities to boas) have only 1. This could mean nothing, or it could mean that boas and pythons possibly developed over time from a completely different animal than any other snake.
So this would beg the question...why would 2 different species develop into something so strange as a legless reptile?
For me this is easy, because I see it every day. If a snake gets loose in my house, he could pass right through my field of vision, and I might not even see him. The body shape is superb for stealth...since they do not have much visual movement for their locomotion...only that we see that they are slowly moving forward. A lizard for example...we would see MUCH more easily...due to the fact that the leg movement would easily give them away.
My boas also have instinctual actions I find intriguing. Before lunging for prey...they will (most of the time) move their head slowly from side to side a few times...like swaying. I thought this to be the snake getting better visual information of how far away the prey is in 3D...the closer the anything is...the more it will move in your vision...while seeing a mountain that is miles away..swaying will do nothing at all...
But then it occured to me that there could be another reason for this. Since the animal is very quick on the draw so to speak...but not quick to chase, camouflage is the best bet. And the swaying could very likely be the snake mimicking a branch in the wind, which would also add to the likelihood of the argument that a snakes appearance, while strange, is a very good tool for an animal to use...the body shape could easily be mistook for a branch or root...which (to me) lends a possible explanation for MORE than 1 animal being the descendents of our current boas and snake.
No boa is poisonous, they instead squeeze the prey and dont allow it to breath, a very successful maneuver...
Other snakes use venom...not very many...but venom is another method that was developed that is very useful.
Make of this information what u will. But to me, I feel that our snakes and boas we see today are descendents of several animals...that now appear to be nearly the same...for the very reason that being that shape and having those skills is useful for the animals success.
And dont mistake the boas and snakes we see today as the "perfected" final form...its still ongoing. We wont see it in our lifetimes, but they will continue to change (like ALL animals) through the years. Not (IMO) because the genes automatically do what is necessary to survive...but rather...that mutations, however small, naturally occur, and they occur for better AND worse...but those mutations that HELP an animal out in some way will more likely be passed on simply due to the animals success at surviving.
Edited by Franatic25, : Edited FACTUAL information of the Caulker's Cay boa.
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