A spatio-temporal decrease in molar size in the western European house mouse

Abstract

a b s t r a c tWe investigate the existence and persistence of a temporal and a spatial gradient in molar size of the house mouse, Mus musculus domesticus, from France, Europe and northern Africa. Specimens include both modern samples extending from the beginning of last century to extant populations as well as archeological material. Several patterns in size variation were evidenced: i) there is a size gradient in molar teeth decreasing from North to South in modern mice, ii) a similar North-South gradient is present in archeological material indicating that it has existed at least since Gallo-Roman times, and iii) there is a decrease in size between the Gallo-Roman samples and modern ones. The geographical gradient was not gradual, but was characterized by a step cline on both sides of the 45 th parallel, that is between the Mediterranean zone and the western European Continent. Within each of these compartments, no latitudinal variation from North to South was observed. The decrease in size of the house mouse since the Gallo-Roman period, or likely since the end of the Middle-Ages, could be due to landscape clearance and expansion of cereal-like cultivations. The commensal way of life, associated with an increase in population density, may have also had an effect.

THE CHANGING PACE OF INSULAR LIFE: 5000 YEARS OF MICROEVOLUTION IN THE ORKNEY VOLE(MICROTUS ARVALIS ORCADENSIS)

“…This suggests that, for M. arvalis at least, body size reduction between fossil and modern specimens has not been a response to long‐term, natural global warming since the LGM (Millien et al ), but rather a more recent anthropogenic phenomenon (Sheridan and Bickford ). A similar trend observed in mice species has been linked with pervasive anthropogenic perturbations—from habitat destruction to climate change (Cassaing et al ; Stoetzel et al )—during very recent times. However, the archaeological record for Mainland Orkney shows size reduction in voles much earlier, between the 4th and 12th centuries AD, suggesting that anthropogenic impacts could have had greater/earlier effects on small mammals in confined/insular environments and/or in higher latitudinal locations.…”

Musin Morocco: a Quaternary sequence of intraspecific evolution

“…Third, anthropogenic action may have modified the environment in a more global way, as the size decrease of wild animals during historical time emerges increasingly as a general feature (Sheridan & Bickford, 2011), also documented in house mice (Cassaing et al, 2011). This might constitute further evidence of the pervasive anthropogenic action, changing environments in many ways including pollution (Nunes, Auffray & Mathias, 2001), habitat destruction, and climate change.…”

A warrant for applied palaeozoology

“…This sort of phenotypic response to environmental change has been documented among many species of rodents in both the Old World and the New World (e.g. Millien, 2004;Smith & Betancourt, 2006;Cassaing et al, 2011). While also documented in NHCs (Pergams & Lawler, 2009), questions remain about cause (Gardner et al, 2011).…”