26The freshwater pearl mussel was historically abundant in many streams and rivers in the Elbe, 27 Oder and Danube Basins in the Czech Republic, Central Europe. By the 21 st century, the mussels 28 had become extinct in the lower and middle altitudes, and current populations are only present 29 near the upper limit of their natural range. The current population of this mussel is estimated to 30 be only 1% of the historical abundance. The population decline was related to the negative 31 impacts of pollution from industry, intense agriculture, forestry and sewage water. The 32 freshwater pearl mussel habitat has also been impacted by watercourse regulations and has been 33 fragmented by dams and weirs. All of these impacts have resulted in failure of the reproductive 34 cycle; the last significant cohort of juveniles settled approximately 30-40 years ago. Therefore, 35 this species is considered critically endangered, and an action plan was developed to conserve the 36 populations in the Czech Republic. Special measures were conducted between 1984 and 2005 to 37 improve the age structure of elderly populations. Fish infected with millions of glochidia were 38 released in two locations, and over 50,000 captive-bred juveniles that were three to five years old 39 were released in 7 locations. Only the latter approach resulted in a small number of subadults that 40 gradually emerged from the substratum to the bottom surface, as confirmed by monitoring efforts. 41Despite simultaneous efforts to restore mussel habitat over the last 25 years, natural reproduction 42 still does not occur in the Czech Republic. Therefore, complete restoration of oligotrophic 43 streams is the key to the future presence and natural reproduction of freshwater pearl mussels in 44 the Czech Republic. 45 46

No abstract

Central Europe faces an influx of terrestrial invertebrates from more southerly regions, in particular from the Mediterranean. This process is particularly noticeable among terrestrial gastropods. In the last 30 years, the number of non-native land snail species found outdoors in the Czech Republic increased from 5 to 15 (8% of all species); more than half of these have presumed Mediterranean origin. The trend has accelerated recently; seven new alien species (six Mediterranean) have been recorded since 2000. As the most recent example, we report the finding of a large helicid species from the South-East Mediterranean, Helix lucorum. A well-established overwintering population was found in Prague, over 400 km from the nearest known localities of the species. This trend of newly established snails corresponds with increases in average temperatures as well as the intensity of foreign trade in the past six decades, suggesting a synergistic effect of both climatic conditions and socioeconomic factors.

The aim of our study is to describe and visualise the spread of two non-indigenous land snail species Cepaea nemoralis and Monacha cartusiana in the Czech Republic during more than 100 years period. Several factors play an important role in changes of the distribution of these species: ecological (climate change), ethological (passive dispersal potencial) and economic (increasing traffic as a vector of spreading). The spreading of M. cartusiana has a rapidly increasing trend. More than half sites in the Czech Republic were colonised by this species in 2000-2010. While the spread of C. nemoralis has been continuous during the last century, the rapid range extension was recorded in the last two decades.