This model simulates the contemporary evolution of Three-spine Stickleback of a stickleback population in a hypothetical lake. This model helps users to explore the changes in allele frequencies resulting from natural selection.
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HOW IT WORKS
HOW IT WORKS
The following processes serve as the underlying mechanisms of the model.
Allele frequencies, genotypes, phenotypes
When setting up the simulation, an equal number of sperms and eggs are generated based on the defined population size and Eda allele ratio. Then individual fish is formed via random fertilization, and the fish genotype is determined by the sperm and egg. Once genotypes are determined, phenotypes are determined accordingly: AA, Aa, and aA produce the complete-armored morph (darker individuals), aa produces low-armored morph(lighter individuals). 5% of individuals are intermediate morph (intermediate color) due to other genetic modifiers. The fewer plates are a stickleback bearing, the faster does it swim (The Bell Lab, 2016; Genetic Science Learning Center, 2017).
Food resource and population size
The stickleback fish needs to obtain energy from the food. The changes in the blue background represent the available food in the lake. The darker the patch is, the less food is available.
Stickleback fish only obtains food from the lighter blue patches, and every move costs some energy. If fish runs out the energy and no food is available from the current patch, it dies.
The slider of "available-food" represents the food resource available for the stickleback population.
The food resource in the hypothetical lake is finite. So individual fish competes for food. Even though they move in the lake randomly, sampling errors still leads to slight unequally food resource for each individual. Therefore even you turn off predation and mutation, allele frequencies will change slightly owing to genetic drift.
Reproduction, inheritance, and mutation
When a fish cumulates a certain amount of energy, it produces gametes following Mendelian rules. These gametes randomly pair to form new individuals. Once turning on the mutation, 5 % alleles "A" and a could mutate to "a" or "A" every tick.
Predation
The "Number-of-predators" determines the number of dragonfly larvae, the predators, existing in the lake. They will prey on the slowest stickleback fish nearby.
THINGS TO TRY
THINGS TO TRY
1. The relationship between the available food and carrying capacity
2. Explore the relationships among allele ratio, number of predators, and mutation.
CREDITS AND REFERENCES
CREDITS AND REFERENCES
This model is made by Dr. Lin Xiang at Weber State University. If you mention this model in a publication, we ask that you include the citations below.
Xiang, L. (2017). Loberg stickleback-Eda gene. Zoology Department, Weber State University, Ogden, UT.
Reference resource:
1. The bell lab: Bridging the Gap Between Developmental Genetics and Paleontology https://www.leonschools.net/site/handlers/filedownload.ashx?modelinstanceid=72882&dataid=106049&FileName=bell%20lab%20article.pdf
2. Stickleback Evolution. Genetic Science Learning Center. (2015, January 7) Learn. Genetics. Retrieved March 21, 2017, from http://learn.genetics.utah.edu/
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