“…To discriminate between the alternative hypotheses of co-speciation versus geographic differentiation, we looked for the presence of parasites of the Heligmosomoides genus in all Apodemus species common in the western Palearctic region: A. sylvaticus, A. flavicollis Melchior1834, A. mystacinus Danford and Alston, 1877, A. uralensis (Pallas, 1811) and A. alpicola Heinrich, 1952 from the Sylvaemus subgenus, as well as A. agrarius (Pallas, 1771) from the Apodemus subgenus Michaux et al, 2002). Multiple Heligmosomoides species were described in Apodemus over continental Europe, including H. skrjarbini Schulz (1926) andH.…”