ALBERT

Description: Non-native species can enter new habitats and ecosystems in a variety of ways. Suitable ecological conditions must exist for non-native species to reproduce in newly colonized habitats. Hot springs are suitable habitats for tropical, aquarium, and ornamental fish species. This paper presents the results of research on the distribution of non-native and native species in relation to environmental factors in the Upper Sakarya Basin, where several such springs are present. The fish fauna in the basin includes native (60% – 21 species, 14 of which are endemic) and non-native (40% – 14 species) fish species. Most of the non-native species (seven species) were found only in warm springs (minimum water temperature 16°C). In addition, 75 fish species belonging to 26 families were found throughout the Sakarya Basin. Hot springs were found to play an important role in the establishment of non-native species. The Kernel Density Estimation (KDE) results revealed that the non-native species density was high in the Upper Sakarya Basin where hot springs are common. This confirms that minimum and maximum temperatures are the main drivers of changes in the distribution of non-native fish species. Two aquarium fishes, Bujurguina vittata and Xiphophorus spp., are reported for the first time in the present study for inland waters of Turkey.

Description: The zebra mussel Dreissena polymorpha is one of the most successful, notorious, and detrimental aquatic invasive non-native species worldwide, having invaded Europe and North America while causing substantial ecological and socio-economic impacts. Here, we investigated the spatiotemporal trends in this species' invasion success using 178 macroinvertebrate abundance 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. polymorpha within invaded communities. Meta-regression models revealed non-significant trends both at the European level and for the majority of the invaded countries, except for France (significant decreasing trend) and Hungary (marginally positive trend). 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 series of 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 associated with the occurrence of D. polymorpha. We also found that higher native richness and lower latitude were related to lower relative abundances. Using Cohen's D as a measure of D. polymorpha impact, we found that biodiversity within the invaded sites was initially higher than in uninvaded ones, but then declined, suggesting differences in biodiversity trends across invaded and uninvaded sites. While our results emphasise the high invasion success of D. polymorpha, increasing stressors within the context 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.