Search

In this study we investigated the emergence patterns of two Systellognatha stoneflies: Perla marginata and P. grandis (Plecoptera: Perlidae) in a first order stream of the Northern Apennines (NW Italy). Exuviae of both species were collected in a selected area of the Curone creek by hand-picking, measuring the distance between river edge and substrate typology. Exuviae were found on different substrate types near the shoreline: stones in the stream bank were mainly used by both species, and gravel beach was the least-utilised substrate. No evident differences were found between the species in the typology and colour of emergence substrates. Interestingly, we found that P. grandis exuviae were significantly located at greater horizontal and vertical distances from the water edge than P. marginata ones. We discuss these findings on the basis of ecological and behavioural considerations. [ABSTRACT FROM AUTHOR]

We examined vertical migration and colonisation patterns of stream macroinvertebrates within the substratum of an Apennine creek in NW Italy. Macrobenthos was sampled at three depths in the streambed (0–5, 5–10, 10–15 cm) by means of artificial baskets filled with natural substratum. We placed 42 traps (5×5×15 cm), i.e. 21 top-opened (T-traps) and 21 bottom-opened (B-traps), each composed of three overlapping baskets (high-H, medium-M and low-L), to evaluate differences in the vertical movements. We also collected Surber samples to compare interstitial assemblages with streambed communities. The multilevel traps yielded 42 taxa, compared with 60 taxa in the natural riverbed. Interstitial traps were rapidly colonised; both taxa richness and organism number increased during the 42-day study period. We found active migration in both vertical directions, but there were more invertebrates in the top-opened traps than in the bottom-opened traps. In the T-traps the most colonised baskets were those placed at the H level, while in the B-traps the L level baskets were more rapidly colonised. The interstitial assemblages differed markedly from the streambed communities in both composition and functional organisation, with more collector-gatherers and predators in the interstitial zone and more filterers and scrapers in the natural riverbed. In Apennine lotic systems, the interstitial zone is an important habitat for stream macrobenthos, although it may not be used by all species. [ABSTRACT FROM AUTHOR]

The main aim of this study, which is based on cover-abundance values of 20 species of floating-leaved and submersed macrophytes collected in 18 lakes located within the River Po catchment basin (Italy), is to investigate the relationships between lake-scale environmental features (including morphology, hydrology, trophic state and water quality variables) and the changes in species composition and species richness in macrophyte communities. The findings reveal that the main changes in community composition of the pondweed communities, identified by principal component analysis, could be effectively explained by a newly introduced morpho-hydrological parameter (the theoretical laminar water renewal rate – RL) and by the trophic state of the lakes, expressed as Carlson's trophic state index (TSI). The results of the multivariate analyses performed also show that the grouping of species is strictly related to growth-form traits. In particular, floating-leaved and submerged macrophytes appeared mutually exclusive in dominating different habitat types defined on the basis of the RL–TSI framework. An increasing trend in species richness was also observed in relation to RL. The possibility of using the bivariate RL–TSI framework for the identification of habitat utilisation patterns by single species was also investigated, and cover-abundance prediction maps based on the RL–TSI framework were produced for several macrophyte species. Observations in another system characterised by high spatial heterogeneity for hydrological and trophic conditions, support the predictions in terms of growth-form prevalence, species richness and single species cover-abundance (where available), and also suggest a more refined application of the proposed approach. [ABSTRACT FROM AUTHOR]