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The demographic history of house mice (Mus musculus domesticus) in eastern North America reveals a close link between human colonization and mouse dispersal.
The house mouse (Mus musculus) has long been known for its ability to thrive alongside humans, making it one of the most adaptable and invasive mammalian species1. This close relationship dates back roughly 12,000 years to when early humans began farming, providing an abundant food source for these rodents2. Today, Mus musculus is widely used in biomedical research due to its physiological similarities to humans and its suitability for laboratory settings3.
Originating from a common ancestor in Asia’s Indian subcontinent, Mus musculus has evolved into different subspecies, with Mus musculus domesticus establishing itself in western Europe4. However, it wasn’t until the last millennium that M. m. domesticus began expanding beyond Western Europe, likely facilitated by human travel, particularly via ships5. The exchange of goods and people between the eastern and western hemispheres during the 15th and early 16th centuries likely introduced M. m. domesticus populations to the Americas5. Despite these historical interactions, the specifics of their spread in eastern North America remain largely unexplored.
A recent study aimed to investigate the demographic history of house mice in eastern North America6. Specifically, researchers sought to determine if the colonization of this region was associated with a sharp reduction in mouse population size (population bottleneck)7, if North American mouse populations displayed mixed ancestry, and when house mice began to colonize North America. To achieve this, the researchers collected 66 DNA samples from wild house mice in both eastern North America and Europe. They focused on five populations in eastern North America (New Hampshire/Vermont, Pennsylvania, Virginia, Georgia, and Florida) and two in Europe (Germany and France), as well as samples from a different subspecies in Spain for comparison. By using advanced sequencing techniques to analyze specific regions of the mouses’ DNA known as exomes, the researchers were able to create a genetic family tree to illustrate the relationships between different house mouse populations over time. This analysis revealed distinct genetic groupings among mouse samples from Europe and eastern North America, with Florida standing out as different from the other North American populations.
Further analysis using principal component analysis (PCA) allowed researchers to visualize genetic similarities and differences between mouse populations, supporting the patterns observed in the family tree. Additionally, ADMIXTURE analysis provided insights into the ancestral origins of each mouse population, revealing high levels of genetic mixing in the Florida population compared to others. Statistical tests reinforced this finding by indicating that Florida experienced multiple introductions, resulting in a mix of genetic traits from both Europe and other North American populations.
When comparing genetic variations among mouse populations in Europe and North America, researchers discovered that European mouse populations had greater genetic diversity between them compared to North American groups. Despite North American mouse populations being widely distributed geographically, they were found to have lower genetic diversity than their European counterparts. This difference suggested a reduction in genetic diversity as European house mice spread to North America, indicating a population bottleneck in the North American mice.
Statistical modeling helped pinpoint the timing of mouse colonization events, showing they occurred within the past few thousand years aligning with periods of human migration to the Americas. Population differences suggested that North American mice diverged within the last 500 years, corresponding with European colonization. This finding suggests a close connection between human and mouse movements. The study revealed that Florida was colonized by mice from different European sources, reflecting a complex history shaped by Spanish and British movements. The researchers also suggested that mice in eastern North America likely originated from unsampled populations in Western Europe, particularly England, due to the prevalence of British influence and migration during the recent colonization of America.
While the recent study provides insights into the demographic history of house mice in eastern North America, there are still questions surrounding their expansion across North America, particularly in regions like Florida. To further explore this topic, the researchers proposed conducting extensive genetic sampling in Europe and North America and combining genetic information with historical data.
Another important aspect to consider is the impact of mouse colonization on native species and ecosystems. Understanding how the introduction of house mice from various sources has affected local biodiversity and ecosystem functions is key to preserving biodiversity and effectively managing ecosystems. Additionally, exploring the influence of human activities such as urban development and changes in land use on the distribution and genetic variation of house mice could offer valuable insights into human-wildlife interactions. The unintentional introduction of invasive species like house mice to new areas can result in the transmission of diseases that threaten human health and native wildlife. By studying the spread of diseases like hantavirus and leptospirosis in relation to the colonization history of house mice, better methods can be developed to protect public health and manage wildlife effectively8.
Ethical considerations in genetic research, particularly with invasive species, are important. Prioritizing animal welfare and respecting Indigenous knowledge and cultural perspectives on wildlife management are essential for fostering trust among researchers, policymakers, and local communities. This trust is fundamental for collaborative efforts to create conservation strategies that balance environmental protection with societal needs and values.
Click here to learn more about the author Taw Meh or contact her at tameh@davidson.edu.
References
1. Morgan, A. P. et al. Population structure and inbreeding in wild house mice (Mus musculus) at different geographic scales. Heredity, 129, 183–194. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9411160/ (2022).
2. Cucchi, T. et al. Tracking the Near Eastern origins and European dispersal of the western house mouse. Scientific reports, 10, 8276. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237409/ (2020).
3. Phifer-Rixey M, Nachman MW. Insights into mammalian biology from the wild house mouse Mus musculus. Elife. 4, e05959. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4397906/ (2015).
4. Suzuki, H. et al. Evolutionary and dispersal history of Eurasian house mice Mus musculus clarified by more extensive geographic sampling of mitochondrial DNA. Heredity, 111, 375–390. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3806020/ (2013).
5. Jones, E. P. et al. Genetic tracking of mice and other bioproxies to infer human history. Trends in Genetics : TIG, 29, 298–308. https://pubmed.ncbi.nlm.nih.gov/23290437/ (2013).
6. Agwamba, K. D., & Nachman, M. W. The demographic history of house mice (Mus musculus domesticus) in eastern North America. G3 (Bethesda), 13, jkac332. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9911051/ (2023).
7. Wein, T., & Dagan, T. The Effect of Population Bottleneck Size and Selective Regime on Genetic Diversity and Evolvability in Bacteria. Genome biology and evolution, 11, 3283–3290. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7145630/ (2019).
8. Marquez, A. et al. House mice as a real sanitary threat of human and animal leptospirosis: proposal for integrated management. BioMed Research International, 2019, 3794876. https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/31341897/ (2019).
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I enjoyed this, Taw Meh! Understanding the historical contexts of genomic data is crucial and I like how you highlighted this. You introduced to us that Mus musculus originated in the Indian subcontinent, dispersing to North America through human colonization, highlighting the unintended consequences of human actions on ecosystems. I agree that preserving ecosystems and biodiversity is crucial, and this is achieved through understanding history. I like how you acknowledged that incorporating knowledgeable communities in the research process can help us gain a fuller picture. We must consider these ethical concerns you brought to better protect and understand our environment.
Great post! Your summarization of this study was wonderful and very digestible, even for someone who may have limited knowledge of biological concepts. Furthermore, this study relates back to the material we are currently studying in class – the epidemiology of COVID. Both studies utilize genomics and records to analyze the distribution of mice and a virus, respectively. It is cool to see how the genetic divergence of a species can align so well with historical records, both in the mice and in COVID as it is transmitted through super spreader events. I’m curious to see more research such as this that combines history with genomics so that more conclusive evidence about the ancestry and the origin of lineages can be determined.