Data from: An invasive species reverses the roles in a host-parasite relationship between bitterling fish and unionid mussels

The impact of multiple invading species can be magnified due to mutual
facilitation, termed “invasional meltdown”, but invasive species can also
be adversely affected by their interactions with other invaders. Using a
unique reciprocal host-parasite relationship between a bitterling fish,
Rhodeus amarus, and unionid mussels, we show that an invasive mussel
reverses the roles in the relationship. Bitterling lay their eggs into
mussel gills, and mussel larvae parasitize fish. Bitterling recently
colonized Europe and parasitize all sympatric European mussels, but are
unable to utilize a recently invasive mussel, Anodonta woodiana. The
parasitic larvae of A. woodiana successfully develop on R. amarus, while
larvae of European mussels are rejected by bitterling. This demonstrates
that invading species may temporarily benefit from a coevolutionary lag by
exploiting evolutionarily naïve hosts, but the resulting relaxed selection
may facilitate its exploitation by subsequent invading species, leading to
unexpected consequences for established interspecific relationships.