Marek Nieoczym

Invasive alien species pose a major threat to ecosystems by outcompeting native species for resources, altering habitats, enabling potential genetic hybridisation and introducing pathogens into the environment. An understanding of the factors that determine virus transfer between invasive and native species is crucial to the mitigation of the negative impact of the pathogens introduced. This study presents a comprehensive analysis of factors influencing Aleutian mink disease virus (AMDV) infection in native mustelids in Poland, following its introduction by feral American mink. AMDV seroprevalence in American mink varied spatially from 0 in the central and southern regions to 0.8 in the northern regions. Antibodies to AMDV were detected in all six studied mustelids, including a novel finding in weasels. AMDV seroprevalence in other mustelids correlated positively with its occurrence in American mink, and reached 0.54 in areas with the highest mink AMDV seroprevalence. Furthermore, in native mustelids, more closely phylogenetically related to mink, AMDV seroprevalence was higher (0.68 in polecats and weasels) compared to more distantly related species (0.37 in badgers). Over the 27‐year study period, AMDV seroprevalence in mustelids has increased from 0.04 to 0.60, despite a decline in seroprevalence in feral mink in subsequent years. These findings suggest that the spread of viral infections as a result of the introduction of invasive species could affect mustelid species and may intensify over time.

Notwithstanding the genus Italobdella has been hypothesized to have doubtful taxonomic value, we decided to update its diagnosis by describing the new species – Italobdella bieleckii sp. n. The leeches were collected from the stony bottom along the shore of the Danube River in Slovakia. In the study, we implemented the model of leech body form and the set of external and internal morphological characters to present the similarity of the new species to the other fish leeches. As a result, we were able to construct the key for determining leeches belonging to the genus Italobdella hoping that the species could be found and determined by other researchers. This would enrich our knowledge about the actual distribution of these leeches and strengthen their systematic position in the genus.

Fish are known to pose strong effects on invertebrate abundance, species richness and assemblage structure. Littoral vegetation may play a crucial role as a refuge for invertebrates vulnerable to fish predation. We studied relative densities and taxonomic composition of water mites, aquatic beetles and bugs in large lake-like ponds with different fish status (fish-free and containing fish) and mesohabitats (emergent littoral vegetation and open water zone). The macroinvertebrate taxa differed in their responses to the fish presence and in mesohabitat preferences. The density and species richness of water mites were greater in fish-containing ponds, while no differences were found between littoral and open-water habitats. In contrast, beetles were far more numerous and species-rich in fish-free ponds and in littoral vegetation. Total densities of aquatic bugs were non-significantly higher in fish-containing ponds, and they preferred littoral areas, but species richness was independent of fish presence and mesohabitat. No statistical interactions between fish presence and the densities of individual macroinvertebrate groups in the littoral habitat were detected, indicating that their use of emergent littoral vegetation was not an antipredator response to fish. The assemblages of the three macroinvertebrate taxa exhibited nested structures of a different order, consistent with their species richness patterns. Our research stresses the importance of littoral vegetation for the distribution and abundance of aquatic insects; however, high fish presence may not affect or may even benefit ecologically important macroinvertebrate groups, such as water mites or bugs.

Aim: Theory predicts that the evolutionary adaptations of prey to reduce predator pressure often fail in confrontation with non‐native predators; thus, their predation usually leads to sharp declines of prey populations. However, over time, prey can develop anti‐predator adaptations, reduce predator impact and recover its population. We analyse the numerical response of multiple prey species to the impact of a non‐native predator on a large spatiotemporal scale.Location: Poland.Methods: Long‐term population dynamics of 13 waterbird species breeding in 123 sites were analysed with reference to the present and historical distribution of mink over 40 years. We rescaled the temporal waterbird dynamics to the time elapsed since the mink colonized each site.Results: The steepest waterbird declines were recorded up to 15 years after establishment of the mink population, and in that period, waterbird abundance averaged across the 13 studied species declined by 50% but certain species showed different patterns: the abundance of eight species declined linearly or nonlinearly, whereas the breeding populations of five other species did not change significantly. Over time, the abundance of some declining species increased slightly and tended to stabilize at a lower level. The temporal pattern of waterbird dynamics averaged across species correlated closely with temporal changes of mink density with a 4‐year time‐lag. A projection of the observed patterns shows that waterbird decline following the expansion of mink has the shape of a wave travelling from the north to the south of Poland.Main conclusions: We conclude that the impact of the invasive American mink should be considered an important factor affecting waterbird populations at a large geographical scale. The waterbird vulnerability to mink predation is species‐specific, and over time the negative impact grows weak as mink population densities decline.

Responses of epibenthic and nektonic macroinvertebrate communities to a gradient of fish size in ponds