Coinvasion and Coinfection: Evolution and adaptation of two invasive parasites infecting blue mussels

Abstract

Biological invasions of parasites offer ideal opportunities to study coevolution in nature - especially when hosts are faced with repeated invasions of parasites. Such coinvasions not only lead to selection on the host but also to selection on parasites arising from direct competition. Here, we present data from a crossed coinfection experiment using two closely related copepod parasites that have invaded the Eastern Atlantic, infecting mussels. One is the specialist Mytilicola intestinalis, that invaded from the Mediterranean Sea in the 1930s and the other one is the generalist Mytilicola orientalis that invaded from Japan in the 1990ies. This system thus offers the opportunity to study host-parasite interactions along a gradient of different coevolutionary timescales and host specificity. Here we report the first results of this experiment on the phenotypic level focussing on the balance and trade-offs between host and parasite traits, i.e. infectivity - virulence for the parasites and virulence-tolerance for the hosts. We find different interactions along these trade-offs between both interactions. We also find that the generalist invader is outcompeting the old invader