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Fitness Group

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House mice (Mus musculus) have spread globally as a result of their commensal relationship with humans. In the form of laboratory strains, both inbred and outbred, they are also among the most widely used model organisms in biomedical research. Although the general outlines of house mouse dispersal and population structure are well known, details have been obscured by either limited sample size or small numbers of markers. Here we examine ancestry, population structure, and inbreeding using SNP microarray genotypes in a cohort of 814 wild mice spanning five continents and all major subspecies of Mus, with a focus on M. m. domesticus. We find that the major axis of genetic variation in M. m. domesticus is a south-to-north gradient within Europe and the Mediterranean. The dominant ancestry component in North America, Australia, New Zealand, and various small offshore islands are of northern European origin. Next we show that inbreeding is surprisingly pervasive and highly variable, even between nearby populations. By inspecting the length distribution of homozygous segments in individual genomes, we find that inbreeding in commensal populations is mostly due to consanguinity. Our results offer new insight into the natural history of an important model organism for medicine and evolutionary biology.



Worldwide, the frequency (pitch) of blue whale (Balaenoptera musculus) calls has been decreasing since first recorded in the 1960s. This frequency decline occurs over annual and inter-annual timescales and has recently been documented in other baleen whale species, yet it remains unexplained. In the Northeast Pacific, blue whales produce two calls, or units, that, when regularly repeated, are referred to as song: A and B calls. In this population, frequency decline has thus far only been examined in B calls. In this work, passive acoustic data collected in the Southern California Bight from 2006 to 2019 were examined to determine if A calls are also declining in frequency and whether the call pulse rate was similarly impacted. Additionally, frequency measurements were made for B calls to determine whether the rate of frequency decline is the same as was calculated when this phenomenon was first reported in 2009. We found that A calls decreased at a rate of 0.32 Hz yr-1 during this period and that B calls were still decreasing, albeit at a slower rate (0.27 Hz yr-1) than reported previously. The A call pulse rate also declined over the course of the study, at a rate of 0.006 pulses/s yr-1. With this updated information, we consider the various theories that have been proposed to explain frequency decline in blue whales. We conclude that no current theory adequately accounts for all aspects of this phenomenon and consider the role that individual perception of song frequency may play. To understand the cause behind call frequency decline, future studies might want to explore the function of these songs and the mechanism for their synchronization. The ubiquitous nature of the frequency shift phenomenon may indicate a consistent level of vocal plasticity and fine auditory processing abilities across baleen whale species.

Citation: Rice A, Širović A, Hildebrand JA, Wood M, Carbaugh-Rutland A, Baumann-Pickering S (2022) Update on frequency decline of Northeast Pacific blue whale (Balaenoptera musculus) calls. PLoS ONE 17(4): e0266469.

The total length of the mouse body is 160-200 mm. The tail measures 78-94 mm and the hind foot measures 17-20 mm. The average weight of an adult is 15-24 g. The skull length is 20.4 to 22.5 mm with width of 10.4 to 11.5 mm (Cory 1912). This is a small mouse with a slender tapering tail. The tail is hairless, scaled in annulations (circular rows). The ears of Mus musculus are large and naked. The nose is pointed, and the fur is course. The color of fur is brownish yellow on the top and gray to buffed on the underside (Jackson 1961).

Mus musculus is located throughout Wisconsin. It may have originated in China, but is now distributed worldwide and lives commensally with humans. It is thought to be introduced in the U.S. from England, about the time of the American Revolution. There is no record of when it was introduced into Wisconsin. Mus musculus has reached an apparently near stable population throughout the United States, twice as abundant Rattus norvegicus (Cory 1912, Jackson 1961, Kurta 1995).

When living with humans, Mus musculus nest in the walls, in storage areas, or in any protected spot near food. Though rarely seen, evidence of its whereabouts is found near human food supplies include chewed boxes, crumbs and piles of feces. It makes its nest out of rags, paper, or anything else that is soft and can be shredded. Most Mus musculus living with humans are active during the day. In the wild Mus musculus is mostly nocturnal, and live in underground burrows with networking tunnels (Cory 1912, Jackson 1961, Kurta 1995). Scientists have observed a cleaning behavior in the springtime, where Mus musculus move winter debris out of its burrow (Schmid-Holmes et al. 2001). Mus musculus is a great runner (8 miles/hr), climber, jumper (up to 8 inches), and swimmer, but usually stays within 50 feet of its home. Mus musculus is omnivorous and drinks water frequently (it also loves milk). The most common predators are cats, weasels, skunks, and a few raptors. It carries several parasites, both internally and externally. Mus musculus is prone to several diseases, and can spread them to humans (Cory 1912, Jackson 1961, Kurta 1995).

Mus musculus can be confused with genera Peromyscus and Reithrodontomys. Mus musculus can be distinguished by the appearance of the tail and the underbelly is usually never white, the molars are in 3 longitudinal rows of smooth tubular incisors. The other two genera have grooved tubular incisors in longitudinal rows of 2 (Cory 1912). 041b061a72


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