Microsporidian infections in the species complex Gammarus roeselii (Amphipoda) over its geographical range: evidence for both host-parasite co-diversification and recent host shifts.

Microsporidians infecting G. roeselii revealed two scenarios of host-parasite associations: (i) ancient associations with vertically transmitted parasites that probably co-diversified with their hosts, and (ii) host shifts from local host species, after the postglacial spread of G. roeselii.