New alien crayfish species in Central Europe - introduction pathways, life histories, and ecological impacts

Biological invasions constitute a leading global threat to biodiversity, second only to habitat loss and degradation. The overall objective of my PhD project was to further our understanding of the drivers, mechanisms, and consequences of biological invasions, by gaining insights into the introduction pathways, life histories, and ecological impacts of new non-indigenous crayfish species (NICS) in Central Europe. New NICS are successful recent invaders of European inland waters, and have considerable potential to cause ecological and economic damage. Specifically, I explored three research topics: (1) invaders for sale: the pet trade as a pathway for new NICS introductions into Central Europe; (2) understanding invasion success: life-history traits of new NICS; and (3) ecological role and impact of new NICS, both from an intra-guild and synecological perspective. My findings suggest that: (1) the pet trade is a major pathway of NICS introductions by generating substantial propagule pressure; (2) r-selected life histories and life-history plasticity support the invasiveness of new NICS; and (3) new NICS are keystone species, which can profoundly alter recipient communities via competition, direct trophic links, and non-consumptive destruction. At high densities, new NICS can completely eliminate susceptible macroinvertebrate and macrophyte species, such as aquatic snails and large, single-stemmed macrophytes. However, other invasive alien species, such as the alien Elodea nuttallii, are less affected by new NICS and may even be indirectly facilitated. New introductions of NICS are likely to be associated with high-risk species, and therefore introduction pathway management is urgently required. Moreover, well-established new NICS should be subjected to control and containment efforts, particularly where they endanger sensitive ecosystems or indigenous crayfish populations