The Influence of Natural Selection on Fur Color Frequency in Wolf-Infested Environments
ABSTRACT
Natural selection is the mechanism by which the proportion of beneficial, heritable characteristics within a population increases over time. We examined the influence of natural selection on fur color frequency in an arctic, predator-infested environment. To do so, we run a PhET simulation of natural selection with the fur color mutations in desert and arctic environments. The white fur trait had a higher frequency than the brown fur trait in the arctic environment, while the brown fur had a higher frequency in the desert environment. Overall, our results demonstrate the power of natural selection in ensuring species maintain the best traits for survival.
INTRODUCTION
Natural selection is the natural process by which organisms that are better adapted to their environment tend to have higher rates of survival and reproduction than those who are less adapted (Gregory, 2009). This tendency leads to an increase in the proportion of beneficial, heritable characteristics within a population over time (Whittaker, 2012). Mutations are the cause of these characteristics; they are changes or errors in genetic material that result in changes to observable characteristics (Whitaker, 2012). Mutations work within the mechanism of natural selection to evolve species to better survive in ever-changing environments.
In this experiment, we tested the influence of natural selection on fur color frequency in predator-infested desert and arctic environments. White fur is the same shade as snow; therefore, we hypothesized that the white fur trait would be more frequent in arctic environments, as the snow would camouflage them from wolves. We also hypothesized that brown fur would be more frequent in desert environments, as the brown fur would blend into the similarly-colored landscape.
METHODS
In the PhET Natural Selection simulation, the arctic was selected as the simulation environment. Then, brown fur was selected as the dominant trait. “Add a Mate” was then selected. After Generation 4, wolves were selected as the environmental factor. Data on the populations of the brown and white fur rabbits was recorded until the simulation was complete. The steps were repeated for a desert simulation environment.
RESULTS
The brown rabbit population in the desert environment increased over time, while that of the white rabbits decreased (Fig.1). These trends are also observed in the frequency of the brown and white fur trait in the rabbit population (Table 1). The end frequency of the brown fur trait is higher than that of the white fur trait (Table 2). For the arctic environment, the brown rabbit population decreased over time, while that of the white rabbits increased; the frequency of the brown and white fur traits in the total population follow the same pattern (Fig. 2, Table 2). In this environment, the end frequency of the white fur trait is higher than that of the brown fur trait (Table 2).
DISCUSSION
The results support our hypotheses that the white fur trait would be more frequent in the population than brown fur in the arctic environment and less frequent in the desert environment. In arctic environments, snow blankets the landscape. Snow, which is white, is similar in shade to the white fur coat of some of the rabbits. This enables them to blend into the environment and not catch the eye of their predators better than brown fur rabbits, which contrast heavily with the white landscape (Jones et al., 2020; Zimova et al., 2014). The higher rate of survival of those with the white fur trait means that they reproduce more than the brown fur rabbits, increasing the frequency of the trait in the rabbit population over multiple generations. These exponential increases are the reason for the brown fur trait being non-existent in the population at the simulation end. This is also the case for the rabbit population in the desert environment, where the sands camouflage the brown rabbits, while the white rabbits are exposed due to the strong background mismatch. Other traits (teeth length, ear rigidity) were controlled for, with all rabbits having straight ears and short teeth; therefore, these traits cannot be considered as causes of the observed results.
LITERATURE CITED
Gregory, T. R. (2009). Understanding Natural Selection: Essential Concepts and Common Misconceptions. Evolution: Education and Outreach, 2(2), 156–175. https://doi.org/10.1007/s12052-009-0128-1
Jones, M. R., Mills, L. S., Jensen, J. D., & Good, J. M. (2020). Convergent evolution of seasonal camouflage in response to reduced snow cover across the snowshoe hare range*. Evolution, 74(9), 2033–2045. https://doi.org/10.1111/evo.13976
Whittaker, D. (2012, October 1). Evolution 101: Natural Selection | BEACON. https://www3.beacon-center.org/blog/2012/10/01/evolution-101-natural-selection/
Zimova, M., Mills, L. S., Lukacs, P. M., & Mitchell, M. E. (2014). Snowshoe hares display limited phenotypic plasticity to mismatch in seasonal camouflage. Proceedings of the Royal Society B: Biological Sciences, 281(1782), 20140029. https://doi.org/10.1098/rspb.2014.0029
FIGURES
| Figure 1. Population totals of white fur and brown fur rabbits from generations 4 to 11 (end of simulation) in desert environment. |
| GENERATION | TOTAL POPULATION | WHITE FUR POPULATION | BROWN FUR POPULATION | % FREQUENCY OF WHITE FUR | % FREQUENCY OF BROWN FUR |
| 4 | 162 | 135 | 27 | 83 | 17 |
| 5 | 103 | 56 | 47 | 54 | 46 |
| 6 | 103 | 26 | 77 | 25 | 75 |
| 7 | 144 | 17 | 127 | 12 | 88 |
| 8 | 234 | 18 | 216 | 8 | 92 |
| 9 | 390 | 23 | 367 | 6 | 94 |
| 10 | 661 | 26 | 635 | 4 | 96 |
| 11 | 1153 | 38 | 1115 | 3 | 97 |
| Table 1. Percent frequency of white fur and brown fur traits in total rabbit population in desert environment. | |||||
| Figure 2. Population totals of white fur and brown fur rabbits from generations 4 to 7 (end of simulation) in arctic environment. |
| GENERATION | TOTAL POPULATION | WHITE FUR POPULATION | BROWN FUR POPULATION | % FREQUENCY OF WHITE FUR | % FREQUENCY OF BROWN FUR |
| 4 | 162 | 137 | 25 | 85 | 15 |
| 5 | 258 | 249 | 9 | 97 | 3 |
| 6 | 456 | 453 | 3 | 99 | 1 |
| 7 | 859 | 0 | 0 | 100 | 0 |
| Table 2. Percent frequency of white fur and brown fur traits in total rabbit population in arctic environment. | |||||
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