Kennedy D. Agwamba

Humans have profoundly influenced the distribution of organisms globally, particularly those that live in close association with human societies. The western house mouse, Mus musculus domesticus, expanded from the Fertile Crescent into Europe several thousand years ago alongside early agricultural societies and was subsequently introduced worldwide through European maritime expansion. Given their close ecological association, human commensals, such as the house mouse, are expected to reflect historic patterns of human movement. Using a dataset of 276 exome sequences of mice sampled from Western Europe, North America, and South America, we reconstruct the demographic history of house mice in the Americas and draw genetic connections to contemporary European population from which they were historically sourced. Admixture graphs reveal that house mice from the Atlantic coast of the Iberian Peninsula are the sister group to all American populations, and a secondary contribution from southern UK populations is evident in North America. Analyses of population structure further support shared ancestry between the Atlantic coast of the Iberian Peninsula and both American continents, between the United Kingdom and North America, between Portugal and Brazil, and between Spain and Argentina. Demographic modeling reveals that American mouse populations diverged roughly within the last 500 years, consistent with the post-15th century arrival of Western European people to the Americas. Together, these results identify Western European mouse populations that share close ancestry with American mouse populations and illustrate how the demographic history of a widespread human commensal species can mirror fine-scale patterns of human migration.

The western house mouse, Mus musculus domesticus , is a human commensal and an outstanding model organism for studying a wide variety of traits and diseases. However, we have few genomic resources for wild mice and only a rudimentary understanding of the demographic history of house mice in Europe. Here, we sequenced 59 whole genomes of mice collected from England, Scotland, Wales, Guernsey, northern France, Italy, Portugal and Spain. We combined this dataset with 24 previously published sequences from southern France, Germany and Iran and compared patterns of population structure and inferred demographic parameters for house mice in western Europe to patterns seen in humans. Principal component and phylogenetic analyses identified three genetic clusters in western European mice. Admixture and f -branch statistics identified historical gene flow between these genetic clusters. Demographic analyses suggest a shared history of population bottlenecks prior to 20 000 years ago. Estimated divergence times between populations of house mice from western Europe ranged from 1500 to 5500 years ago, in general agreement with the zooarchaeological record. These results correspond well with key aspects of contemporary human population structure and the history of migration in western Europe, highlighting the commensal relationship of this important genetic model.

The Western European house mouse (Mus musculus domesticus) is a widespread human commensal that has recently been introduced to North America. Its introduction to the Americas is thought to have resulted from the transatlantic movements of Europeans that began in the early 16th century. To study the details of this colonization history, we examine population structure, explore relevant demographic models, and infer the timing of divergence among house mouse populations in the eastern United States using published exome sequences from five North American populations and two European populations. For North American populations of house mice, levels of nucleotide variation were lower, and low-frequency alleles were less common than for European populations. These patterns provide evidence of a mild bottleneck associated with the movement of house mice into North America. Several analyses revealed that one North American population is genetically admixed, which indicates at least two source populations from Europe were independently introduced to eastern North America. Estimated divergence times between North American and German populations ranged between ∼1,000 and 7,000 years ago and overlapped with the estimated divergence time between populations from Germany and France. Demographic models comparing different North American populations revealed that these populations diverged from each other mostly within the last 500 years, consistent with the timing of the arrival of Western European settlers to North America. Together, these results support a recent introduction of Western European house mice to eastern North America, highlighting the effects of human migration and colonization on the spread of an invasive human commensal.