You are studying a population of dragonflies looking at 2 alleles labeled X 1 an

Question

You are studying a population of dragonflies looking at 2 alleles labeled X1 and X2. In your new season of fieldwork you find 53 of the 472 individuals you examine have a new allele, X3. It seems very unlikely that a new mutation would be found in that many individuals.

A. (1 pt.) What seems like the most likely hypothesis to explain the presence of this new allele in your study population?

B. (2 pts.) How would you test this hypothesis in the field? Outline how you would test the hypothesis, but do not go into a step by step detail.

Explanation / Answer

A. The most likely hypothesis to explain the presence of this new allele in the study population would be the gene flow (also known as the gene migration). The gene pool changes happen because of one of the four factors, i.e., mutation, migration, genetic drift, and natural selection. Since the possibility of mutation is ruled out only remaining option would be migration because the natural selection and genetic drift can only explain the genetic diversity and not the sudden detection of a new allele.  

B.  Wright's equation F = 1/ (1+4Nm)  is one of the most influential theories used till today to determine the probability of gene flow. In the island model, we assume that migration brings in entirely unrelated genes from infinitely many other islands or from an infinitely large mainland, with probability m. Thus, the chance that any allele in a particular generation has not immigrated is (1-m), and the probability that neither of the two alleles chosen has immigrated in that generation is (1-m)2. Nm is is the fraction of the population x the number within that population, it represents the "number of migrants" into a population. For this reason, a crude estimation can be taking Nm as measures of "gene flow". However, this method has some limitation as it does not describe the type of gene flow. So essentially, tracking the number of individuals by random grab method and marking and re-grabbing to determine the number of migrants is the best possible and simplest option available.

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