The beach mouse (Peromyscus polionotus) is a small rodent found in the southeastern United States. Coat color in the beach mouse is variable, from dark brown to blonde (Figure 1). A pigment called eumelanin is responsible for some of the diversity in mouse coat color. The MC1R gene, located on chromosome 8, plays a major role in the synthesis of eumelanin. There are two alleles of MC1R: R allele. Results in a functional MC1R protein that leads to stimulation of pigment production. This allele is found in dark colored mice. C allele. Results in a non-functional MC1R protein. Pigment production is, as a result, not stimulated. This allele is found in light colored mice. Figure 1. Beach mouse with light fur (left) and dark (right). These mice are hunted by visual predators like owls and fox. The distribution of coat color is not random. Beach mice with dark fur are found further inland, on dark brown soils while mice with light fur are found on beaches, where the sand is light brown. Dark fur mice also have to compete with another mouse species (Peromyscus maniculatus) that inhabits a similar ecological niche. Question: Evolutionary biologists believe that ancestral populations of beach mice likely had dark fur. As mice migrated to white sandy beaches, which color would likely have greater fitness? Briefly explain your reasoning.
The beach mouse (Peromyscus polionotus) is a small rodent found in the southeastern United
States. Coat color in the beach mouse is variable, from dark brown to blonde (Figure 1). A pigment called eumelanin is responsible for some of the diversity in mouse coat color. The
MC1R gene, located on chromosome 8, plays a major role in the synthesis of eumelanin. There are two alleles of MC1R:
- R allele. Results in a functional MC1R protein that leads to stimulation of pigment production. This allele is found in dark colored mice.
- C allele. Results in a non-functional MC1R protein. Pigment production is, as a result, not stimulated. This allele is found in light colored mice.
Figure 1. Beach mouse with light fur (left) and dark (right).
These mice are hunted by visual predators like owls and fox. The distribution of coat color is not random. Beach mice with dark fur are found further inland, on dark brown soils while mice with light fur are found on beaches, where the sand is light brown. Dark fur mice also have to compete with another mouse species (Peromyscus maniculatus) that inhabits a similar ecological niche.
Question:
Evolutionary biologists believe that ancestral populations of beach mice likely had dark fur. As mice migrated to white sandy beaches, which color would likely have greater fitness? Briefly explain your reasoning.
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