Background: Mice of the genus Apodemus are one the most common mammals in the Palaearctic region. Despite their broad range and long history of ecological observations, there are no whole-genome data available for Apodemus, hindering our ability to further exploit the genus in evolutionary and ecological genomics context.Results: Here we present results from the whole-genome, high-density genotyping using double-digest restriction site-associated DNA sequencing (ddRAD-seq) on 72 individuals of A. flavicollis and 10 A. sylvaticus from four populations, sampled across 500 km distance in northern Poland. Our data present clear genetic divergence of the two species, with average sequence divergence, based on 21377 common loci, of 1.51% and an evolutionary rate of 0.0019 substitutions per site per million years. We provide a catalogue of 117 highly divergent loci that enable genetic differentiation of the two species in Poland and to a large degree of 20 unrelated samples from several European countries and Tunisia. We also show evidence of admixture between the three A. flavicollis populations but demonstrate that they have negligible average genome-wide population structure, with largest pairwise F ST < 0.086.
Conclusion:Our study demonstrates the feasibility of genome-wide, high-density genotyping in Apodemus and provides the first insights into the population genomics of one of the species. 1 2 Background 3 Mice of the genus Apodemus (Kaup, 1829) (Rodentia: Muridae) are one the most 4 common mammals in the Palaearctic region [43]. The genus comprises of three 5 subgenera (Sylvaemus, Apodemus and Karstomys) [43], however the systematic 6 classification of the 20 species belonging to the genus [16] is not fully settled [36]. 7 In the Western Palearctic, the yellow-necked mice A. flavicollis (Melchior, 1934) 8 and the woodmice A. sylvaticus (Linnaeus, 1758) are widespread, sympatric and 9 occasionally syntopic species. They are often difficult to distinguish morphologically 10 in their southern range [30], but in the Central and Northern Europe both are 11 easily recognisable by the yellow collar around the neck of A. flavicollis, absent in 12 A. sylvaticus. 13 Their prevalence in Western Palearctic and common status in Western and Central 14 Europe made them one of the model organisms to study post-glacial movement of context, as one of the vectors of Borellia-carrying ticks Ixodes ricinus, who often feed 17 on Apodemus [13, 61], tick-borne encephalitis virus [47] and hantaviruses [33, 50] 18 and have been used as markers for environmental quality [40, 66]. Lastly, they 19 have extra-autosomal chromosomes, called B chromosomes, with varied distribution 20 among the populations [59] but unknown role, although it has been suggested they 21are involved in cellular metabolism [34, 39].
22Previous studies on Apodemus typically employed a small number of microsatellite 23 [62] and mtDNA markers [24, 42, 44, 45], which are insufficient to learn about the 24 species' population structure and admixture patterns in detail,...