Information about biotic interactions (e.g. competition, predation, parasitism, diseases, mutualism, allelopathy) is
fundamental to better understand species distribution and abundance, ecosystem functioning, and ultimately guide
conservation efforts. However, conservation planning often overlooks these important interactions. Here, we aim to
demonstrate a new framework to include biotic interactions into Marxan. For that, we use freshwater mussels and
fish interaction (as mussels rely on fishes to complete their life cycle) in the Douro River basin (Iberian Peninsula)
as a case study. While doing that, we also test the importance of including biotic interactions into conservation
planning exercises, by running spatial prioritisation analysis considering either: 1) only the target species (freshwater
mussels); 2) freshwater mussels and their obligatory hosts (freshwater fishes); 3) freshwater mussels, fishes and their
interactions.With this framework we found that biotic interactions tend to be under represented when the data on both
freshwater mussels and fishes is not simultaneously included in the spatial prioritisation. Overall, the priority areas
selected across all scenarios are mostly located in the western part of the Douro River basin, where most freshwater mussels and fishes still occur. Given the low overlap of priority areas identified here and the current Natura 2000 network,
our approach may be useful for establishing (or enlarging) protected areas, especially in light of the EU Biodiversity
Strategy for 2030. Also, this work may provide guidance for future habitat restoration and management of
main threats to freshwater biodiversity.
