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Aim: Invasive alien species are a growing problem worldwide due to their ecological, economic and human health impacts. The "killer shrimp" Dikerogammarus villosus is a notorious invasive alien amphipod from the Ponto‐Caspian region that has invaded many fresh and brackish waters across Europe. Understandings of large‐scale population dynamics of highly impactful invaders such as D. villosus are lacking, inhibiting predictions of impact and efficient timing of management strategies. Hence, our aim was to assess trends and dynamics of D. villosus as well as its impacts in freshwater rivers and streams. Location: Europe. Methods: We analysed 96 European time series between 1994 and 2019 and identified trends in the relative abundance (i.e. dominance %) of D. villosus in invaded time series, as well as a set of site‐specific characteristics to identify drivers and determinants of population changes and invasion dynamics using meta‐regression modelling. We also looked at the spread over space and time to estimate the invasion speed (km/year) of D. villosus in Europe. We investigated the impact of D. villosus abundance on recipient community metrics (i.e. abundance, taxa richness, temporal turnover, Shannon diversity and Pielou evenness) using generalized linear models. Results: Population trends varied across the time series. Nevertheless, community dominance of D. villosus increased over time across all time series. The frequency of occurrences (used as a proxy for invader spread) was well described by a Pareto distribution, whereby we estimated a lag phase (i.e. the time between introduction and spatial expansion) of approximately 28 years, followed by a gradual increase before new occurrences declined rapidly in the long term. D. villosus population change was associated with decreased taxa richness, community turnover and Shannon diversity. Main Conclusion: Our results show that D. villosus is well‐established in European waters and its abundance significantly alters ecological communities. However, the multidecadal lag phase prior to observed spatial expansion suggests that initial introductions by D. villosus are cryptic, thus signalling the need for more effective early detection methods. [ABSTRACT FROM AUTHOR]

Macroinvertebrate assemblages of temporary ponds are ideal model systems to explore biodiversity patterns and metacommunity ecology. In addition, the study of the environmental variables driving such biodiversity patterns is essential in establishing proper guidelines for the conservation of the singular fauna of temporary ponds, especially since such ponds are vulnerable systems., We analysed the macroinvertebrate assemblages and environmental characteristics of 80 ponds spread across the Doñana National Park, SW Spain to (i) analyse macroinvertebrate β-diversity and metacommunity structure; and (ii) discern the main environmental and spatial drivers of these patterns., The pond network was highly heterogeneous as temporary ponds were highly variable. Macroinvertebrate β-diversity partitioning showed that species replacement made the greatest contribution to total β-diversity while the contribution of nestedness was small. The macroinvertebrate community structure and β-diversity were similarly driven by: electrical conductivity (and co-variables alkalinity, pH, and ion concentrations), plant richness (and the co-variable pond surface area), maximum depth, marsh, and coastal proximity as well as two spatial descriptors extracted from Moran's eigenvector maps. The spatial descriptors indicated that large interpond distances were involved, suggesting that species dispersal limitations only take place over long distances in the area., Those taxa that departed from the general nested pattern, termed idiosyncratic, significantly contributed to the maintenance of high pond network diversity through the species replacement and occurred within particular environmental conditions in the pond network., These results reveal that environmental heterogeneity and connectivity are key factors in the preservation of high macroinvertebrate diversity in nested pond networks with high numbers of idiosyncratic species. [ABSTRACT FROM AUTHOR]

The article presents a study which evaluates the inter-annual variability in the composition of amphibian assemblages in a Mediterranean temporary pond in Doñana National Park. A detailed framework is provided to assess temporal turnover from data of an opposing nature and to identify variation in species richness from changes in abundance and identity of species. The study reported that the amphibian assemblages showed high inter-annual variability during the four-year study period.

1. The zooplankton (rotifer and microcrustacean) assemblages of temporary ponds in the Doñana National Park (south-west Spain) have been compared in two surveys of contrasting scales that resulted in the same number of samples: an extensive survey of 36 ponds sampled in May 1998 (or widespread survey) and a survey of nine ponds sampled four times over 2 years (or cumulative survey). 2. The total number of microcrustacean and rotifer taxa was larger in the cumulative survey (43 and 41 taxa, respectively) than in the widespread survey (39 and 34, respectively). Crustacean assemblages became less alike throughout the cumulative survey. 3. The presence of invertebrates (Coleoptera, Odonata, Heteroptera and crayfish) and aquatic vertebrates (fish and salamanders) was recorded as an estimate of potential predator impact on zooplankton. Several pond features (water depth, conductivity, pH, chlorophyll a concentration, distance to the nearest permanent pond and to the marsh) were also measured in both surveys. 4. A combination of these environmental factors was more strongly related to the similarity matrices derived from the zooplankton assemblages of the cumulative survey (Rho = 0.7) than to those of the widespread survey (Rho < 0.4). The distance of ponds to the marsh was an important factor in explaining this correlation as well as the strongest factor in the ordination of crustacean assemblages following a CCA. 5. Predation by exotic fish in long-hydroperiod ponds where overflow drains to the nearby marsh (fish source) is the mechanism likely to explain the changes in crustacean composition recorded in the cumulative survey. 6. The cumulative survey was more suitable for the study of zooplankton diversity as it rendered a higher number of taxa and gave more insight into the mechanisms that explain taxon richness. Thus, conservation strategies in temporary habitats require a scale of observation that includes long temporal changes. [ABSTRACT FROM AUTHOR]