Predicting climatic threats to an endangered freshwater mussel in Europe: the need to account for fish hosts

• Published in: Freshwater Biology
• Main Authors: Silva, Janine P. da, Gonçalves, Duarte Vasconcelos, Lopes-Lima, Manuel, Anastácio, Pedro M., Banha, Filipe, Frimpong, Emmanuel, Gama, Mafalda, Miranda, Rafael, Reis, Joaquim, Filipe, Ana Filipa, Sousa, Ronaldo Gomes
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: Climate change; Conservation; Freshwater pearl mussel; Margaritifera margaritifera; Mussels-fish relationship; Species distribution models; Science & Technology; Salmo salar
• Online Access: https://hdl.handle.net/1822/83086; https://doi.org/10.1111/fwb.13885

The freshwater pearl mussel Margaritifera margaritifera has been suffering major population declines in Europe. This endangered species is a host specialist and exclusively requires salmonid species (Salmo trutta and Salmo salar) to complete its life cycle. In theory, obligatory biotic interactions should deserve special conservation attention, because the loss or massive decline of fish hosts may elicit the extirpation of their affiliated species. While many threats disturbing M. margaritifera are similarly affecting salmonids, climate change is particularly alarming, with the potential to significantly change the fish-mussel dynamics. To evaluate the importance of including the occurrence of fish hosts for predicting the distribution of M. margaritifera in Europe, three datasets were used to build species distribution models (SDMs) with a maximum entropy (MaxEnt) approach: (1) environmental variables (ENV); (2) probability of fish hosts occurrence (FH); and (3) environmental variables and probability of fish hosts occurrence (ENV + FH). We identified the environmental variables that better explain M. margaritifera distribution and modelled its current and future distribution under a suite of climate change scenarios. Furthermore, projections were used to evaluate the adequacy of current networks of European protected areas in covering the suitable habitats for M. margaritifera. Results showed that incorporating data about fish hosts into M. margaritifera SDMs avoided the overprediction of geographical projections and, to a minor extent, improved model performance (area under the curve: ENV = 0.851; FH = 0.848; ENV + FH = 0.867). The distribution range of M. margaritifera in Europe is expected to contract in all future timeframes and emission scenarios considered. Forecasts point to large contractions particularly in central and southern Europe and lowland regions. The European network of protected areas fails to protect 69% of the current and 66%–67% of the future predicted M. margaritifera distribution. This ...