User:BCBulldog2023/White-footed mouse

Adaptations to urbanization in New York City

Native populations of P. leucopus in New York city are isolated by dense human infrastructure and are largely confined to small urban forest islands such as Prospect Park and Central Park. The limited gene flow caused by human activities and coupled with a bottleneck event in urban populations has been powerful enough to lead to evolutionary divergence of urban white-footed mice.

Metabolism

New York City mice exhibit local adaptations to diet-mediated selective pressures of urban habitats. Being opportunistic feeders, urban P. leucopus populations subside on food discarded by humans as a readily available source of nutriment, thereby consuming a lot more fat and carbohydrates than rural populations. Results of a landscape genomics study showed evidence of positive selection in mitochondrial genes of urban mice that are responsible for lipid and carbohydrate breakdown and digestion. Isolated P. leucopus populations inhabiting NYC parks show signs of molecular-level adaptation to urban food resources. The differential evolution of metabolic processes in urban P. leucopus populations is thought to contribute to their success and survival in NYC urban forests. Furthermore, the morphology of urban white-footed mice may be changing to adapt to to alternative food sources. For instance, the teeth of white-footed mice in New York City are shorter than the teeth of rural mice. This change in physical traits could be explained by the availability of higher-quality food sources in urban forests, which negates the need for long, powerful teeth.

Detoxification

Urban populations of P. leucopus may be under unique selective pressures due to increased routine exposure to pollutants and toxins. A comparative transcriptome study found evidence of positive selection acting on the genes of urban mice that play major roles in detoxification and xenobiotic metabolism. The genes under positive selection pressure include CYPA1A and Hsp90, which are known to be involved in the metabolism of foreign substances and drugs. High concentrations of heavy metals such as lead and mercury in NYC park soils pose a unique selective pressure that likely led urban populations of P. leucopus to develop metabolic adaptations to the toxicity of urban forest environments. Furthermore, exposure of pollutants is known to induce hypermethylation of DNA. A study showed that in urban white-footed mice, a gene coding for a demethylase enzyme is under positive selection. This means that urban populations of white-food mice that live in highly polluted environments uniquely benefit from an active demethylase enzyme that removes methyl groups from DNA.

Reproduction

City-dwelling white-footed mouse populations are densely concentrated in isolated urban parks, which makes sperm competition a particularly powerful source of selection in urban environments. Genetic studies have identified signs of molecular-level evolution of reproductive processes in urban white-footed mouse populations. Genes associated with spermatogenesis, sperm locomotion, and sperm-egg interactions in urban mice show a divergent pattern of regulation compared to their rural counterparts. Therefore, the intensified sperm competition of dense mouse populations in urban forests has driven them to develop faster, more efficient sperm than that of rural mice.

Immunity

Urban environments are saturated with large numbers of novel and familiar pathogens that are introduced by transportation, traffic, and trade. The elevated occurrence of pathogens is a driver of directional selection in which genetic variants that more efficiently resist infection are favored. The outcome of this selection can be seen in genetic divergence between urban and rural P. leucopus populations at loci that regulate the innate immune response and inflammation. Furthermore, a study has found evidence of positive selection acting on genes that modulate pathogen recognition in urban mice. Immunoregulatory proteins that are found on T lymphocytes are overexpressed in urban mice when compared to rural populations. These findings suggest that the immune systems of NYC white-footed mice may be evolving to recognize and respond to pathogens more efficiently. The divergence between rural and urban white-footed mice is especially prominent due to impeded gene flow between these populations, which is caused by landscape barriers including roads, highways, and pedestrian sidewalks. Monitoring the strength of immune defenses in P. leucopus is of special importance because they are commonly infected with dangerous pathogens such as hantaviruses and Borrelia burgdorferi.