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Summary1. Beta diversity is the compositional heterogeneity of biotic assemblages among sites, and biotic homogenization is the decrease in beta diversity, facilitated by an increase in similarity of biotic communities over time. Environmental harshness decreases the importance of stochastic processes in structuring assemblages, resulting in a homogenization of the biota. 2. We investigated if increasing nutrient enrichment, land-use pressure, and within-lake habitat alteration would decrease the beta diversity of macroinvertebrates in 46 lakes across Europe. Beta diversity was calculated using global multivariate dispersion. We utilized a structural equation modelling approach to account for hierarchical interdependence between potential impacts, that is the direct effects and correlations among the different impacts. 3. We found clear indications that European macroinvertebrate communities are being homogenized by ongoing lake shore development. Increasing land-use pressure in the form of residential and commercial development had a direct negative effect on beta diversity (standardized coefficient = À0Á40), as did roadways, albeit indirectly through an increase in engineering structures (standardized coefficient = À0Á31). Increasing within-lake silt levels also homogenized macroinvertebrate communities (standardized coefficient = À0Á18), independent of near shore land use. Our results indicate the negative effect of both the near shore landuse pressure and the within-lake habitat alteration on macroinvertebrate beta diversity, with significant interactions between these pressures. 4. Habitat protection should take a more holistic approach to assessing lake development pressure, over a range of scales, as a solely site specific approach is not always biologically meaningful. Thus, future management plans should carefully control and mitigate ongoing development pressure if lake ecosystem health and resilience is to be maintained. 5. Synthesis and applications. This study is the first of its kind to demonstrate European-wide homogenization of littoral macroinvertebrate lake communities with increasing habitat alteration and land-use pressure. Significant interactions occur between different habitat scales, with no one scale entirely accounting for the homogenization effect. To avoid further biotic homogenization, development pressure must be carefully managed at multiple scales, and where possible, minimized. This presents a challenge, as globally there is an increasing expansion of the human population and a consequent increase in anthropogenic pressure across all habitats.

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Information on the distribution and vulnerability of invertebrates is often scarce and, as a consequence, this group of organisms is usually neglected in conservation studies. Yet it is possible to reasonably infer ranges and vulnerabilities of species and establish spatial conservation priorities, even with incomplete information. We investigated conservation priorities of hoverflies in Southeast Europe based on species distribution models (SDM) and vulnerability indices. Species distribution models were used to compensate for the lack of knowledge on species ranges. Measures related to geographical rarity, endemism and habitat specialisation were used to assess species vulnerability. Potential distribution and three alternative vulnerability indices were used to calculate two spatial conservation indices: potential Biodiversity Conservation Concern index (pBCC) and potential Biodiversity Conservation Weight (pBCW). pBCC highlighted areas with a large proportion of highly vulnerable species, even where species richness was low, such as the Danube delta and mid‐Aegean islands. It also identified potentially important areas yet‐to‐be surveyed (e.g. Carpathian mountains), which might deserve future conservation measures. pBCW emphasised areas hosting high richness of both vulnerable and resilient species, such as the eastern Aegean Islands and the eastern part of Crete. We demonstrate that: (i) it is possible to establish conservation priorities at large scales if SDM and simple vulnerability measures are combined; (ii) complementary approaches are necessary to emphasise the importance of areas with different characteristics; and (iii) several understudied areas should be targets of future sampling schemes to confirm their importance for the conservation of hoverfly diversity in Southeast Europe.

This paper is a result of the project WISER (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery) funded by the European Union under the 7th Framework Programme, Theme 6 (Environment including Climate Change) (contract No. 226273), http://www.wiser.eu. We thank Daniel Graeber for help with the statistical analysis.

The antimicrobial activity of five crude extracts of the freshwater bryozoan Pectinatella magnifica (Leidy, 1851) was evaluated in vitro for the first time. P. magnifica acetone extract exhibited the highest antibacterial activity (minimum inhibitory concentrations (MIC) 0.004-0.350 mg/mL and MBC 0.007-0.500 mg/mL), while its methanol extract showed the most promising antifungal activity (MIC 0.03-0.12 mg/mL and MFC 0.06-0.25 mg/mL). Furthermore, at a concentration of 0.25 MIC, the methanol extract reduced biofilm formation of the bacterial strain Pseudomonas aeruginosa PAO1 in a considerable extent (59.14%). FTIR spectra of the most active extracts indicate the presence of carbonyl compounds, long-chain alcohols and/or sterols. According to the experimental data obtained, P. magnifica methanol extract may be considered as a good resource of novel natural products with potent antibiofilm activity against the bacterium well known for its resistance.

460 PLANOJEVIĆ et al. diment risk assessment procedures integrates the effects of multiple stressors and gives a realistic insight into not only sediment contamination by toxic pollutants, but also the sediment status in general.