Coevolution in Reptiles

Coevolution is generally defined as a change in the genetic composition of one species in response to a genetic change in another species. The key to a coevolutionary relationship between two species is that a particular trait in each species has evolved as a direct result of the interaction between the two species. Although the concept of coevolution has been present in the Origin of Species theory for some time, the term itself is typically attributed to a study of butterflies on plants by Ehrlich and Raven (1964). In their study, Ehrlich and Raven showed that plant compounds determined their usage by butterflies. There are countless examples of coevolution between two or more organisms, with the most drastic ones stemming from host-parasite interactions.

Coevolution can act in different ways, depending on the nature of the interaction between the species involved. One mode of coevolution involves coevolutionary arms races between two given species, in which each species involved continuously evolves more efficient means of attack or defense, as a direct result of the interaction with the other species. For example, a study by Geffeney et al (2002) showed that populations of the Common Garter Snake (Thamnophis sirtalis) have evolved a resistance to the toxins of their prey, newts of the genus Taricha. As the newts continue to evolve more potent toxins, the garter snakes evolve an increased amount of resistance to the poison. Anytime that one of the two species has an advantage, selection favors those individuals that can equalize that advantage. The strength of selection is geographically variable, depending on a range of ecological factors, including resource availability and geographic structure (Brodie et al, 2002). This is a process called “geographic mosaic theory of evolution” (Thompson, 1994).

Cases of predator-prey coevolution with deadly toxins and predator resistance are rather unique. An organism that is toxic to its predator does not derive an immediate benefit from this trait, if it is killed by the predator. Conversely, predators that die from the consumption of the prey item are unable to evolve a degree of resistance against the toxins. Therefore, the outcome must be variable to both species, in order for a coevolutionary relationship to develop. Becky et al (2002) showed that snakes assessed their own resistance relative to newt toxicity, and rejected newts that were deemed too toxic.

Another example is that of the Australian Broadheaded Snake (Hoplocephalus bungaroides), a relatively small member of the venomous Elapidae family that feeds primarily on velvet geckos (Oedura lesueurii). Downes and Shine (1998) demonstrated that velvet gecko populations that are sympatric with this snake species have evolved the ability to detect and react to the scent of this predator. Their experiments showed that the geckos are significantly less likely to enter rock crevices if the scent of the snake was distributed in the area. In turn, the snake has evolved to remain sedentary for extended periods of time, which minimizes the extent to which its scent is spread over the rocks. Furthermore, they showed that while specimens from populations of geckos that are sympatric with the snake predator react to the scent, those that came from allopatric populations did not. Additionally, the geckos did not respond in the same manner to other snake species that do not prey on geckos. These examples demonstrate that those particular traits have evolved in response to the appropriate trait in the other species, as a product of the predator-prey interaction.

Another form of coevolution is the competitive interaction between two species. In those cases, two species continuously coevolve to outcompete the other one for resources. For example, two species of salamanders of the genus Plethodon occur in sympatry in the Great Smokey Mountains, where they compete for resources. This is indicated by the fact that the removal of one species leads to an immediate increase of population size in the other. Adams and Rohlf (2000) found significant morphological differentiation in sympatric populations that was determined to be associated with a reduction in food consumption and prey segregation, whereas allopatric populations showed no differences in resource uses. These morphological differentiations were found to relate to functional and biomechanical differences in jaw closure. Since these differences in jaw closure are associated with the differences in prey consumption, this case of character displacement links changes in form with changes in function (Adams & Rohlf, 2000).

While these cases have been instances of pairwise coevolution, that is, a coevolutionary process between two species, there are also numerous cases, in which multiple interacting lineages have influenced one another in some reciprocal manner (Weiblen 2003). For example, different taxa of insects may attack a particular plant lineage. However, such processes among broad groups of taxa are still based on interactions between individual sets of two species, and the degree of interconnection between the sets of pairs may vary significantly. Regardless of the nature of the interspecific relationship, genetic components and a phenotypic variation in traits that influence the cost and benefit of the interaction for each involved species must be prevalent for coevolution to occur (Weiblen 2003). Phylogenetic analysis is an important component of coevolution.

Recent research in this field has focused on coevolution and its maintenance of maladaption (Thompson et al, 2002), as well as its dynamics among geographically structured populations (Thompson 1997). Blatrix & Herbers (2003) demonstrated host specificity and geographical variation between slave-making ants and their hosts. Mutualism (Pellmyr 2003; Tschapka 2003) and the coevolutionary interactions between hosts and parasites have also been subject of much recent study. For example, Nuismer et al (2003a) recently showed that parasite adaptation is inversely proportional to the fraction of its host's distribution range that it occupies. This mechanism may limit a parasite's distribution range, as it becomes increasingly maladapted to the host. In another study, Nuismer et al (2003b) showed that gene flow is not required for generating empirical patterns as predicted by the geographic mosaic theory. Restif and Koella (2003) presented a model that entails shared control by the host and the parasite in determining the traits of the relationship. In predator-prey interactions, Kopp and Tollrian (2003) showed possible evidence for interaction between an inducible defense and an inducible offence in ciliates, one of the first examples of reciprocal phenotypic plasticity in such context.

In conclusion, coevolution is an area, in which ecology, genetics and phylogeny interact. The endless inter- and intraspecific interactions between the countless organisms leave much to be discovered, as scientists have likely merely scratched the surface to understanding the complex interactive structures that form the engine to evolutionary processes.

References

Adams DC, Rohlf FJ. 2000. Ecological character displacement in Plethodon: biomechanical differences found from a geometric morphometric study. Proc Natl Acad Sci U S A. 2000 Apr 11;97(8):4106-11.

Becky LW, Brodie ED Jr, Brodie ED III. 2002. Coevolution of deadly toxins and predator resistance: self-assessment of resistance by garter snakes leads to behavioral rejection of toxic newt prey. Herpetologica: Vol. 59, No. 2, pp. 155-163.

Blatrix R, Herbers JM. 2003. Coevolution between slave-making ants and their hosts: Host specificity and geographical variation. Molecular Ecology, October 2003, Vol. 12, iss. 10, pp. 2809-2816

Brodie ED Jr, Ridenhour BJ, Brodie ED 3rd. 2002. The evolutionary response of predators to dangerous prey: hotspots and coldspots in the geographic mosaic of coevolution between garter snakes and newts. Evolution Int J Org Evolution. 2002 Oct;56(10):2067-82.

Ehrlich P.R and P. H. Raven. 1964. Butterflies and plants: a study in coevolution. Evolution 18:586-608.

Geffeney S, Brodie ED Jr, Ruben PC, Brodie ED 3rd. 2002. Mechanisms of adaptation in a predator-prey arms race: TTX-resistant sodium channels. Science. 2002 Aug 23;297(5585):1336-9.

Kopp M, Tollrian R. 2003. Reciprocal phenotypic plasticity in a predator-prey system: Inducible offences against inducible defences? Ecology Letters, August 2003, Vol. 6, iss. 8, pp. 742-748

Nuismer, SL; Thompson, J N; Gomulkiewicz, R. 2003a. Coevolution between hosts and parasites with partially overlapping geographic ranges. Journal of Evolutionary Biology, November 2003, Vol. 16, iss. 6, pp. 1337-1345

Nuismer, SL; Gomulkiewicz R; Morgan, MT. 2003b. Coevolution in temporally variable environments. American Naturalist, August 2003, Vol. 162, iss. 2, pp. 195-204

Pellmyr, O. 2003. Yuccas, yucca moths, and coevolution: A review. Annals of the Missouri Botanical Garden, Winter 2003, Vol. 90, iss. 1, pp. 35-55

Restiff O, Koella JC. 2003. Shared control of epidemiological traits in a coevolutionary model of host-parasite interactions. American Naturalist, June 2003, Vol. 161, iss. 6, pp. 827-836

Thompson JN. 1994. The Coevolutionary Process. Chicago: University of Chicago Press.

Thompson JN. 1997. Evaluating the dynamics of coevolution among geographically structured populations. Ecology. 1997 78(6):1619-1623

Thompson JN, Nuismer SL, Gomulkiewicz R. 2002. Coevolution and Maladaptation. Integ. And Comp. Biol., 2002 42:381-387

Tschapka, Marco. 2003. Pollination of the understorey palm Calyptrogyne ghiesbreghtiana by hovering and perching bats. Biological Journal of the Linnean Society, October 2003, Vol. 80, iss. 2, pp. 281-288

Weiblen, GD. 2003. Interspecific Coevolution. Encyclopedia of Life Sciences.

Member Comments: Add A Comment

Coevolution in Reptiles	Reply
Anonymous post on January 9, 2005	Mail this to a friend!
While there are instances in nature where we can find evidence of coevolution to some extent, I believe many of the relationships between prey and species should be considered 'learned behavior' or 'conditioned response' as opposed to 'coevolution.' For the sake of discussion, we can use the relationship between the Austrailian Broadhead Snake and the Velvet Gecko. I believe the statement was, "Velvet Gecko populations that are sympatric with this snake species have 'evolved' the ability to detect and react to the scent of this predator." Wouldn't this simply be the ability of this particular gecko to learn to stay away from this snake, in much the same way we learn not to step out in front of a speeding car? Food for thought - that has coevolved with my ability to think and reason for myself... Just a ponder...

RE: Coevolution in Reptiles	Reply
by BitisG on January 30, 2005	Mail this to a friend!
This is all adaptation at work. Athough these are reptiles with no "paternal bonds" ,specifically, having no "parents" to learn from. Case in point, the Broad Headed Snake and Velvet Gecko. I agree that that is a display of learned behavior. They still have instics that will cause them to "learn" each others behavior while co-existing in the same environment. However the garter snake and toad that is adaptation in the sense of a built up immunity to the toxin over time. This is not co-evolution.

Coevolution in Reptiles	Reply
by ChurleR on February 11, 2005	Mail this to a friend!
Actually, resistence to toxins and increased toxicity is coevolution, the newts would have no reason to increase their toxicity nor the snakes to increase their resistence if they weren't living together. He's not talking about resistance building over a period of a year, he's talking about resistance to toxins and hence toxicity building over generations. This means the newts that weren't toxic enough got eaten, the ones that were overly toxic survived, and pread their genes, and vise versa. That's all basic evolution is.

RE: Coevolution in Reptiles	Reply
Anonymous post on April 7, 2005	Mail this to a friend!
Science is never religiously neutral. Science deals with cause and effect. Unless one makes the dogmatic presupposition that causes can only be natural, it must be said that causes can be either natural or supernatural. In the case of the origin of the universe, the origin of life, and the appearance of most, if not all, new species, science can show us no natural causes. In the case of the universe, direct proof now exists that the cause, or causer, must transcend matter, energy, length, width, height, and time. In other words, the causer must be supernatural. If this is true, then one must assume that the fossil record can be interpreted in 2 ways. Either evolution is true, or a supernatural being created life in quantum leaps. Why is it okay for evolutionists to defy the law of maximum entropy, but other disciplines may not? Take your pick, but I must ask, where are all of the transitional fossils that tie all of these species together? The lack of transitional fossils cannot be explained as being due to the scarcity of material can it? No, the deficiencies are real, and they will never be filled. Have you ever met an evolutionist that was researching information that would undermine the theory? They aren't looking for that data, and therefore will never arrive at a fully educated conclusion.

RE: Coevolution in Reptiles	Reply
by Nightflight99 on November 1, 2005	Mail this to a friend!
The anonymous post was way off-topic, but so satured with misinformation that it actually deserved a response. Actually, religion is outside of the realm of science. Science operates on a set of particular rules (i.e. scientific method) and is based on evidence, whereas religion is based on faith, and therefore a tautology. Because religion fails to pass even the easiest of scientific tests, explanations that are based on faith are not alternatives to scientific laws, despite the constant attempts of religious groups to pass them off as such. Furthermore, statements such as "In the case of the universe, direct proof now exists that the cause, or causer, must transcend matter, energy, length, width, height, and time. In other words, the causer must be supernatural" offer little except evidence of selective reading. It is most ironic that some people will refuse to accept evolution at large, but gladly acknowledge changes in allele frequencies. There is nothing wrong with religious beliefs, but to attempt to pass them off as science is not only misleading, but also demonstrating a lack of understanding of science and the rules that it is based upon.

RE: Coevolution in Reptiles	Reply
by Coralsnayk on December 4, 2008	Mail this to a friend!
Let’s pick this apart. The anonymous poster said… “Science is never religiously neutral. Science deals with cause and effect.” Science’s findings may have implications to religions. But the observations that science makes, and the questions that it asks are not religious in quality. Science does not (because it cannot) address the question, “Was a deity the cause of this?” Therefore, since it does not take a stance in assumption either way on questions of this kind, it is neutral with respect to religion. Science, and indeed, logical thought as a whole, deal with cause and effect. In this sentence, anonymous was correct. Anonymous continued, “Unless one makes the dogmatic presupposition that causes can only be natural, it must be said that causes can be either natural or supernatural.” There is no such dogmatic presupposition in science. Science is not dogmatic, but instead, tentative, pending better evidence. If something is thought of as supernatural and then is later understood, it is then included in the realm of nature. We call nature that which we can observe, perceive, study, and objectively test. If something is supernatural, then it by definition, it exists outside of nature, therefore we cannot observe it, perceive it, study, test it or make any definitive pronouncements about its existence. There may be a super (or sub) natural realm that actually exists, but until such a time as it is observable, science will be neutral with respect to the parameters or the existence of such things. Indeed, those who posit the existence of such things bear the burden of evidence. Evidence, not proof, but I'll get to that in a minute. Anonymous continued, “In the case of the origin of the universe, the origin of life, and the appearance of most, if not all, new species, science can show us no natural causes.” The origin of the universe is known as the Big Bang. We KNOW this because we can still see the movement of the expansion happening. The rate of expansion of the universe is actually accelerating, not slowing down. How and why this originated is not known and may never be known since we may not travel back in time and observe the initial event. Further evidence is forthcoming, however. The origin of life is known as abiogenesis. That organic molecules can be formed from non-organic components is an observed FACT. Creationists/Intelligent Design advocates often and incorrectly claim that science asserts that the first simple chemical replicators were anything as complex as a modern cell or even a primitive bacteria species. This is not a claim science makes or defends. Speciation events have been OBSERVED. Examples: Oenothera, Tragopogon miscellus, Drosophila melanogaster, Tribolium castaneum. Science is NOT an “us and them” mentality. It is self-critical, self-correcting, and tentative. These are its strengths. Because of this, science DOES NOT claim absolute inerrancy. You may say, “Well one has to be right, and the other has to be wrong.” A scientist would reply, “No, we may both be wrong. Let’s follow the evidence.” Anonymous continues, “In the case of the universe, direct proof now exists that the cause, or causer, must transcend matter, energy, length, width, height, and time. In other words, the causer must be supernatural.” Science is not the venue for proof. Scientists do not “do” proof. Nothing outside of mathematics is ever proven. When you say “proof”, perhaps you mean evidence. When you say “direct”, perhaps you mean observable. Therefore, if your claim of “direct proof” is in fact, observable evidence, would you perhaps elucidate what that is? Has it hit the peer-reviewed journals, if not the newspaper headlines? As far as such “proof” of a cause or causer… if he/she/it transcends the qualities of existence that we can observe, and indeed, the continuum in which we are thoroughly embroiled, how can there be evidence that we can perceive IN this continuum? Anonymous: “If this is true, then one must assume that the fossil record can be interpreted in 2 ways.” This is not known to be true, so there is no need to interpret the fossil record in any way that is inconsistent with the scientific method. Parsimony demands that the interpretation with the most explanatory power, but with the least requirement of assumption is to be preferred. Anonymous: “Either evolution is true or a supernatural being created life in quantum leaps.” Evolution is an observed fact (anyone may KNOW that populations change with respect to their collective genomes, through reproduction and death) and requires no assumptions. Supernatural beings are not observed facts. Note that evolution – the natural phenomenon – is not the same as Evolutionary theory which defines, describes and makes predictions about the natural phenomenon. Anonymous: “Why is it okay for evolutionists to defy the law of maximum entropy, but other disciplines may not?” What is an evolutionist? If you mean scientist, then say scientist. Do you call the same number of people who accept that gravity exists, “Gravitationists” or “Newtonists”? Do you call weathermen “precipitationists” because they accept that the observed natural phenomenon, rain, occurs? By the law of maximum entropy, I assume you mean the 2nd law of Thermodynamics. I don’t know of anyone would want to defy this law. I don’t know anyone who can defy a law of physics, for that matter. Perhaps the confusion lies in your understanding of that law. First of all, it involves closed systems. This, straight away disqualifies the earth or anything upon it. The earth is receiving energy from the sun constantly and therefore is NOT a closed system. However, the law simply states that in a closed system (which the earth is not), the sole result of an interaction between a cold body and a warmer body cannot be a transfer of thermal energy from the cold to the warmer. Again, this does not apply to natural processes on the earth, because energy is constantly being added to the earth from the sun. The law is not defined in terms of disorder, however, disorder and entropy can sometimes be correlated. Anonymous: “Take your pick, but I must ask, where are all of the transitional fossils that tie all of these species together? The lack of transitional fossils cannot be explained as being due to the scarcity of material can it?” No need to pick or choose. The current understanding has explanatory power and is sufficient, pending introduction of new, robust evidence. Fossils, if they exist, are in the ground or have been collected and not yet described. Where else could they be? The fossil of any animal from a population that has speciated is a transitional fossil. Perhaps you mean intermediate fossil. Thousands of these have been found. Why do you assert that lack of [intermediate] fossils cannot be explained by scarcity of material? That makes no sense. Is a lack of fossils not, by definition a scarcity of material? Nevertheless, many intermediates are lacking. They may have never fossilized or we may have not yet found them. This does not offset the validity of the ones we HAVE found. Archaeopteryx and Tiktaalik are both excellent examples of intermediates. The first is an intermediate with traits of both non-avian dinosaurs and avian dinosaurs, and the second is an intermediate tetrapod with traits common to both lobe finned fish and amphibians. Anonymous: “No, the deficiencies are real, and they will never be filled.” If you expect the fossil record to be as complete as a video surveillance of several millions of years, then you are correct. You are also bound to be disappointed. Do you also have a problem accepting that a person that you met as a baby and then not again until he was an adult is the same person, if you don’t have pictures for every day of his life in between? If you were handed only a few pictures instead of a complete video account of the person's intervening years, would you say that the person existed in [quantum](why quantum?) leaps and bounds? Somehow I don’t think so. So it is the case, then, with ancestral and modern populations. And lastly, Anonymous: “Have you ever met an evolutionist that was researching information that would undermine the theory? They aren't looking for that data, and therefore will never arrive at a fully educated conclusion.” To my knowledge, I have never met an evolutionist. If you mean scientist, then yes. Science does that all the time. It is called intellectual honesty. It is called Peer review. It is a necessary first step in science to attempt to falsify your own hypothesis. The next step is not to research data to support your hypothesis, but to ask OTHER scientists in the relevant field to ALSO falsify it. Good scientists don’t look for only the data that will bolster their hypotheses. Good scientists follow ALL the evidence to its conclusion. This may not be “fully educated” as humans cannot know all things. But it is, at least intellectually honest and rigorously learned.

Coevolution in Reptiles	Reply
by SueP on April 21, 2011	Mail this to a friend!
The relationship between the newt and the garter snake is a classic example of coevolution. It is an "evolutionary arms race" if you will. BTW: Religion cannot ever be scientific; the very foundation of science is to gather evidence, test hypotheses and find patterns in nature. Those who try to use science as a religious tool start at the end; to take a belief and try to find evidence to support that and only that belief - this is not science. Science does not have an agenda, creationists do, and it's not scientific.

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