Habitat mediates coevolved but not novel species interactions

On-going recovery of native predators has the potential to alter species interactions, with community and ecosystem wide implications. We estimated co-occurrence of three species of conservation and management interest from a multi-species citizen science camera trap survey. We demonstrate fundamental differences in novel and co-evolved predator-prey interactions that are mediated by habitat. Specifically, we demonstrate that anthropogenic habitat modification had no influence on the expansion of the recovering native pine marten in Ireland, nor does it affect the predator’s suppressive influence on an invasive prey species, the grey squirrel. In contrast, the direction of the interaction between the pine marten and a native prey species, the red squirrel, is dependent on habitat. Pine martens had a positive influence on red squirrel occurrence at a landscape scale, especially in native broadleaved woodlands. However, in areas dominated by non-native conifer plantations, the pine marten reduced red squirrel occurrence. These findings suggest that following the recovery of a native predator, the benefits of competitive release are spatially structured and habitat specific. The potential for past and future landscape modification to alter established interactions between predators and prey has global implications in the context of the on-going recovery of predator populations in human-modified landscapes.