Understanding the complex dynamics of zebra mussel invasions over several decades in European rivers: drivers, impacts and predictions

Abstract

The zebra mussel Dreissena polymorpha is one of the most successful, notorious, and detrimental aquatic invasive non-nativespecies worldwide, having invaded Europe and North America while causing substantial ecological and socio-economicimpacts. Here, we investigated the spatiotemporal trends in this species’ invasion success using 178 macroinvertebrate abun-dance time series, containing 1451 records of D. polymorpha collected across nine European countries between 1972–2019.Using these raw (absolute) abundance data, we examined trends and drivers of occurrences and relative abundances of D. poly-morpha within invaded communities. Meta-regression models revealed non-significant trends both at the European level andfor the majority of the invaded countries, except for France (significant decreasing trend) and Hungary (marginally positivetrend). At the European level, the number of D. polymorpha occurrences over time followed a flat-top bell-shaped distribution,with a steep increase between 1973–1989 followed by a plateau phase prior to significantly declining post-1998. Using a seriesof climatic and hydromorphological site-specific characteristics of invaded and uninvaded sites from two periods (1998–2002;2011–2015), we found that native richness, non-native abundance, distance to the next barrier, and elevation were associatedwith the occurrence of D. polymorpha. We also found that higher native richness and lower latitude were related to lower rela-tive abundances. Using Cohen’s D as a measure of D. polymorpha impact, we found that biodiversity within the invaded siteswas initially higher than in uninvaded ones, but then declined, suggesting differences in biodiversity trends across invadedand uninvaded sites. While our results emphasise the high invasion success of D. polymorpha, increasing stressors within thecontext of global change – particularly ongoing climate change – are likely to enhance invasion rates and the impact of D.polymorpha in the near future, exacerbated by the lack of timely and effective management actions.