Genetic differentiation of the house mouse around the Mediterranean basin: matrilineal footprints of early and late colonization

Abstract

The molecular signatures of the recent expansion of the western house mouse, Mus musculus domesticus, around the Mediterranean basin are investigated through the study of mitochondrial D-loop polymorphism on a 1313 individual dataset. When reducing the complexity of the matrilineal network to a series of haplogroups (HGs), our main results indicate that: (i) several HGs are recognized which seem to have almost simultaneously diverged from each other, confirming a recent expansion for the whole subspecies; (ii) some HGs are geographically delimited while others are widespread, indicative of multiple introductions or secondary exchanges; (iii) mice from the western and the eastern coasts of Africa harbour largely different sets of HGs; and (iv) HGs from the two shores of the Mediterranean are more similar in the west than in the east. This pattern is in keeping with the two-step westward expansion proposed by zooarchaeological data, an early one coincident with the Neolithic progression and limited to the eastern Mediterranean and a later one, particularly evident in the western Mediterranean, related to the generalization of maritime trade during the first millennium BC and onwards. The dispersal of mice along with humans, which continues until today, has for instance left complex footprints on the long ago colonized Cyprus or more simple ones on the much more recently populated Canary Islands.

Phylogeny and adaptation shape the teeth of insular mice

“…(iv) Tenerife appeared more related to a Southern European haplogroup, a signature of exchanges between the Canaries and the Spanish realms [14]. Evidence of mixing exist on Madeira and all three Canary islands investigated ( figure 1; electronic supplementary material, figure S2): typical Tenerife haplotypes seldom occur on Madeira, El Hierro and La Palma, and vice versa.…”

“…(ii) Guillou shared its only haplotype with other mice from Kerguelen Archipelago and Western European specimens from England, Germany and France, and from harbours on the way to the Southern Ocean as in Cameroon [25]. [14]. This genetic assignation has been interpreted as related to a possible introduction by Danish Vikings onto Madeira [45], mice being later translocated to the Canaries by Portuguese travels.…”

“…This set was down-sampled to 90 mice for 3D morphometrics, including only animals with relatively unworn teeth (table 1). The sampling included continental Western Europe and contrasted insular settings (figure 1a): Northern Atlantic (Orkney Archipelago), Macaronesian islands in the sub-tropical mid-Atlantic region (Madeira and Canary Archipelagoes [14,22]), and the sub-Antarctic region (Marion Island; Guillou Island from the Kerguelen Archipelago [23]). All individuals were considered as adults and sub-adults based on the criterion that the third molars were fully erupted, which occurs at weaning.…”

“…Because Western European populations display a complex genetic structure [14,15], island populations will exhibit a variable genetic signature, depending on the colonization source and subsequent demography, which is itself related to human history [16]. Island house mice thus offer a model to investigate the relative importance of population history, adaptation and stochastic events on phenotypic evolution [9].…”

Cryptic diversity in Black rats Rattus rattus of the Galápagos Islands, Ecuador

“…2011; Bonhomme et al. 2011). In particular, the Black Rat ( Rattus rattus ) is among the world's worst invasive species (Lowe et al.…”