Résumé
Following human occupation, the house mouse has colonized numerous
islands, exposing the species to a wide variety of environments. Such a
colonization process, involving successive founder events and bottlenecks,
may either promote random evolution or facilitate adaptation, making the
relative importance of adaptive and stochastic processes in insular
evolution difficult to assess. Here, we jointly analyse genetic and
morphometric variation in the house mice (Mus musculus domesticus) from
the Orkney archipelago. Genetic analyses, based on mitochondrial DNA and
microsatellites, revealed considerable genetic structure within the
archipelago, suggestive of a high degree of isolation and long-lasting
stability of the insular populations. Morphometric analyses, based on a
quantification of the shape of the first upper molar, revealed
considerable differentiation compared to Western European populations, and
significant geographic structure in Orkney, largely congruent with the
pattern of genetic divergence. Morphological diversification in Orkney
followed a Brownian motion model of evolution, suggesting a primary role
for random drift over adaptation to local environments. Substantial
structuring of human populations in Orkney has recently been demonstrated,
mirroring the situation found here in house mice. This synanthropic
species may thus constitute a bio-proxy of human structure and practices
even at a very local scale.