Snake evolution

Shine R, Reed RN, Shetty S, Lemaster M, Mason RT (2002) Reproductive isolating mechanisms between two sympatric sibling species of sea snakes. Evolution 56 1655-1662... 

Shape-dependent curvature velocity. The effect of curvature velocity is to slow down the snake evolution at places of high curvature, effectively smoothing out the sharp corners that may otherwise be formed. 

Gans, C. (1965) Empathic learning and the mimicry of African snakes. Evolution, 18, 705. 

Brodie, E. D., Jr., Ridenhour, B. J., and Brodie, E. D., III. (2002). The evolutionary response of predators to dangerous prey hotspots and coldspots in the geographic mosaic of coevolution between garter snakes and newts. Evolution 56,2067-2082. 

Evolution is tireless in the development of natural toxins. A vast number of variations are possible with even a small number of amino acids in peptides, and peptides make up only one of a broad array of toxic compounds. For example, the predatory marine snail genus Conus is estimated to include at least 500 different species. Each species kills or paralyzes its prey with a venom that contains 50-200 different peptides or proteins. Furthermore, there is little duplication of peptides among Conus species. Other animals with useful toxins include snakes, frogs, spiders, bees, wasps, and scorpions. Plant species with toxic (or therapeutic) substances are too numerous to mention here they are referred to in many chapters of this book. 

The theory of evolution provides answers to many questions pertaining to every day fife. For instance, why are we afraid of certain animals but not of others The simple answer is that some animals are more dangerous than others, i.e. certain types of spiders or snakes are very dangerous. Therefore, it makes sense that many people are afraid of these types of animals. People who like to play with spiders or snakes may have had a slightly lower reproduction rate because some of them died when playing with these animals. 

Greene HW (1997) Snakes The Evolution and Mystery in Nature. Los Angeles University of California Press. 

Snakes are amongst the most feared of aU creatures simply because a handful of species are lethal to humans. It is perhaps a forhmate quirk of evolution that snakes strike fear into us, because this means that we leave them alone. On the other hand some harmless snakes, for example the Common Water Snake (Nerodia sipedon) from north America, are killed because they look like dangerous species (in this case the dreaded Water Moccasin or Cottonmouth Agkistrodon piscivorus)). This is an unfortimate quirk of evolution, because the Brown Water Snake has evolved to mimic the dangerous Water Moccasin in the hope of frightening away potential predators. The outcome, however, as far as humans are concerned, is quite the opposite. 

There is one, as yet, unsolved mystery in the snake world. Surely when snakes evenomate they swallow a small amount of their own poison, and when they eat their prey that has been killed by their own lethal injection they ingest these lethal chemicals. Why then are snakes not killed by their own toxins This is perfect evolution. The snakes produce some of the most lethal poisons in the world, but appear to be immune to their effects. 

O It is interesting that Nature s evolution has not yet provided the Brazilian lancehead snake with venom peptides, which contain thiol groups as higher affinity ligands for complexing zinc. 

Phenotypic, genetic and environmental correlations between chemo-receptive responses to prey in the garter snake, Thamnophis elegans, Evolution, 35 489. 

The problem we will address in this paper is how the status or suitability of the female as a mate is communicated to the male garter snake. We will also discuss how our findings contribute to an understanding of the evolution of chemical communication in vertebrates. 

I review the role of trailing in these social activities, discuss how snakes orient to pheromone trails and describe some aspects of the evolution of trail pheromones. 

An optimal group in which to examine trail pheromone evolution is the garter snakes of the Thamnophis radix complex. In the United States, this complex consists of six recently evolved but distinct species radix,... 

It appears from these studies that pheromone trail specificity played an early role in the evolution of species reproductive isolation in Thamnophis. Behavioral assays of trail specificity of a variety of snakes would be valuable as they may be important clues to ancestral relationships of snakes and the ecological pressures during their evolution. 

Although the database from experimental studies of pheromone trailing behavior in snakes is small, it is apparent from this review that such work is quite valuable in evaluating the role of olfaction in snake sociobiology. Trailing activity can be used as an easily quantified visual bioassay of chemosensory input relating to the various social responses of snakes. In addition, aspects of this activity may be useful in other disciplines of herpetology (i.e., evolution and taxonomy). 

Before delving into the evolution of various kinds of mimicry, we should explore a facet of mimicry barely touched upon above sympatry, or the idea that all models, mimics, and predators must co-exist (at least figuratively within the memory span of the predator) if successful learning is to be feasible. Most often attention has been focused on geographic sympatry. This subject has been examined extensively by Sheppard (1959), Ford (1975), and Turner (1975) and will not be discussed here beyond calling attention to two vertebrate examples of accurate sympatry coral snakes (Greene and McDiarmid, 1981) and salamanders (Huheey and Brandon, 1974). 

---