Silent enemies: can low-virulence macroparasites drive disease-mediated invasions?

Shared pathogens can alter the interaction between native and alien species resulting in disease-mediated invasions (DMIs). Invasive animals often harbour low-virulence macroparasites, but empirical evidence for macroparasite-driven DMIs is still limited due to their subtile pathological impacts and scarce prominence. Here, we modelled the dynamics of native red squirrels, invasive grey squirrels and their shared nematode Strongyloides robustus to assess whether macroparasites can drive DMIs and lead to native species extinction. Our simulations showed that spill-over of the alien parasite can lead to red squirrel extinction, that grey squirrels can amplify the infection in the native host and that the infection can accelerate the replacement of red squirrels compared to direct competition alone, ultimately facilitating invasion by grey squirrels. These results show that low-virulence macroparasites can potentially mediate animal invasions, suggesting that we are overlooking key drivers of native species decline.