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Biased Gene Conversion and the Evolution of Bedbugs

From flying bug, much like a mosquito, to bedbug...According to my hypothesis, several thousand years ago human beings displayed animal life, and this caused the flying bug to specialize in biting human beings (a bug has to eat somewhere). The bedbug is not a 'randomly mutated million year old bug' but is a brand new bug, and the human race is being 'spanked' by this bug for wrecking its environment.
The evolution of bedbugs
The evolution of bedbugs
A graphic displaying the stages of the evolution of bedbugs (from a long skinny tubular shaped flying bug, to the modern round shaped bedbug). None of the insects are 'fossils' but rather they coexist and intermiediate forms are seen simulataneously as gene transfer modifies the body design of the insect. One argument made against this hypothesis is that these are 'different species of insect', but these insects are capable of mating, and produce offspring that lie somewhere on the continuum between 'long skinny bug' and 'round bedbug', and are therefore the same species, so this argument is invalid.

Gene Conversion: A nonsynonymous reciprocal recombination process that results in one region of DNA becoming identical with another.
Recombination: The exchange of DNA between molecules, resulting in the formation of new sequences.
Nonsynonymous: Substitutions that result in amino acid replacements are said to be nonsynonymous while substitutions that do not cause an amino acid replacement (such as a GGG to GGC change - both codons still encode glycine) are said to be synonymous substitutions.
Biased Gene Conversion: Gene conversion where genetic information tends to flow more in one direction than in the other.

The following is a brief commentary on the Principles of Evolution: A Study in the Evolution of Bedbugs.

The evidence suggests that it is reasonable to formulate an hypothesis that describes the evolution of bedbugs as consisting of an older stage and a newer stage (the bedbug is species of insect which is currently undergoing the process of evolution, and thus is a living laboratory for the study of how evolution really does work).

In an earlier stage the bedbug acquired such adaptations as the syringe mechanism loaded with anesthetic (the bite of a bedbug is painless). This allows the insect to bite without running the risk of the human host being awakened. This must be a very old adaptation since all bedbugs possess this characteristic (both the older, more primitive bedbugs, with the long tubular body shape, and the more modern round bedbugs).

There is currently a small suite of genetic adaptations and these genes are being distributed throughout the bedbug population. These include the genes for being a flat bedbug, the genes for being a round bedbug, and the genes for a discrete bite, absent the swelling associated with the more primitive bedbug bite. When a primitive (elongated, tubular shaped insect) comes into contact with the genes for 'flatness' and 'roundness' the insect produces offspring that are perfectly flat and the insect begins to take on a rounded shape (the result is an elongated, perfectly flat insect, which also displays swelling around the abdomen). I therefore interpreted the genes for 'flatness' and 'roundness' to be 'dominant genes', and evolution then becomes the process by which a species undergoes a transformation by means of disseminating such dominant genes throughout the population.

I have also noticed that the gene for a discrete bedbug bite does not seem to be 'dominant', in that a more primitive insect can mate with a more modern bedbug and the result is a bedbug which has the modern body type, but has inherited the gene for the primitive bite from the more primitive insect. This represents a real step backwards for the bedbugs, in that the gene for a discrete bite (no swelling or redness, it is merely a discrete puncture hole) is a genetic adaptation as important as the introduction of anesthetic. It should be true that such an important adaptation should be passed on in the form of a 'dominant gene' and it should also be true that it should be impossible for more primitive insects to defeat this new adaptation by passing along the genes for a more primitive bite. The swelling and soreness associated with this primitive bite defeats all the other stealthy adaptations made by previous generations of bedbugs, and for this reason we could describe the gene for a discrete bite as being a 'primary characteristic' while a gene for being 'flat' or 'round' we could describe as being a 'secondary characteristic'. Why would we see genes for 'secondary characteristics' having the property of being 'dominant genes' while such an important gene for a 'primary characteristic', which is being disseminated at the same time, display the property of being a 'recessive gene'.

We seldom see elongated, tubular shaped bedbugs today. This body shape has been deprecated and has almost completely disappeared. However there is anecdotal evidence to suggest that there is a mixed population of bedbugs as far it concerns this gene for the discrete bite as compared to the gene for the swollen welt. You hear many reports of nasty bites and you hear many reports of discrete puncture wounds with no associated swelling or redness. This would indicate that the gene for a discrete bite, a very important adaptation, is a newer gene and has been more recently introduced into the population.

This leads me to form the following speculative hypothesis. We speak of the genetic code and therefore we might import certain concepts from computational science. We will make the assumption that a gene includes 'a time stamp' or a 'counter'. Each time a gene is transferred, a counter is incremented. Those genes which have survived for many generations then become 'dominant genes' and it would be at this time that we would begin to see evidence for 'biased gene transfer'. We would no longer see a primitive bed bug passing along the gene for a primitive bite to a more modern bedbug, but rather there would be a 'biased' transfer of genes that would favor the more modern bed bug and which would deprecate the genetic contribution of the insect with the older adaptations. Now the older insect has the 'oldest genes', but the more modern insect has the 'novel' genes, and once these introduced genes have 'rolled over the counter' to a certain point, they are assumed to be 'good choices', and therefore we would see 'biased gene conversion'.

Following this line of reasoning we could assume that genes for flatness and roundness are 'dominant genes' because they have been around for a longer time (the counter has rolled over more times) while the gene for a discrete bite is not yet 'dominant' because it is still to novel (the counter has not yet rolled over an adequate number of times).

This process of 'counting transfers' could also explain speciation among fish. For example there are something like a couple of dozen species of clown fish. They have different designs painted upon their bodies. Now let us assume that a male clown fish has a body design that a female clown fish prefers. She mates preferentially with this male, and the result are mixed offspring (some look like her, some look like the male, and some are a combination). This process repeats itself many times, and as it does the gene for this 'body painting', being a novel gene, has a counter incremented each time it is transferred. As time goes by it becomes a 'dominant gene' and we begin to see 'biased gene transfer' in that all the offspring begin to resemble the male, while the contribution of the female is deprecated. More time goes by, and even though the clown fish were not geographically separated, even so they become a separate species through the process of persistent preferential mating.

Thanks 15.Feb.2009 09:43


Its nice to see something like this here, esp since the bedbug is becoming such a problem again in multi-unit dwellings in Downtown Portland. In your research have you come across info on what methods of eradication hold the most promise?