Laura Marziali

Chironomids from Southern Alpine running waters: ecology, biogeography

The chironomid fauna living in running waters in the Southern Alps was investigated from an ecological and biogeographical point of view: 202 species were identified (not including terrestrial species). It must be emphasised that species identification is tentative within some genera, especially those awaiting revision (e.g., Boreoheptagyia, Chaetocladius). Although much taxonomic work was done in the past on the chironomid Alpine fauna, there are still many unsolved problems. Most of the species found are widespread in the Palearctic Region, with no evidence of bio-geographical barriers separating different Alpine sectors. Really a relatively high number of species reported from the northern and western side (France, Switzerland, Austria) of the Alps was not captured on the southern side (Italy), whereas most species found on the southern side are also present on the northern one. Very few species are reported from southern side only. Lack of sampling, imperfect taxonomic knowledge and different environmental conditions between the northern and southern sides may be responsible of this result. A comparison of the fauna of the southern Alps with the fauna of the Apennines suggests that the differences are probably more related to ecological conditions (lack of glaciers in the Apennines) than to biogeographical barriers. Different chironomid assemblages colonise manifold habitat types: strict cold-stenothermal species tolerating high current velocity (e.g., Diamesa latitarsis – steinboecki group) are almost the sole inhabitants of kryal biotopes, while other cold-stenothermal species are restricted to cold springs (Diamesa dampfi, D. incallida, Tokunagaia rectangularis, T. tonollii), there are also species characteristic of hygropetric habitats (Syndiamesa edwardsi, S. nigra) or restricted to lacustrine habitats (Corynoneura lacustris, Paratanytarsus austriacus). It must be emphasised that different responses to environmental factors can be observed between species belonging to the same genus (e.g., Diamesa, Eukiefferiella, Orthocladius , Paratrichocladius), so species identification is really needed for a good ecological work. Water temperature, current velocity, substrate type are the most critical factors, sometime chironomid species appear to be rather opportunistic and their presence or absence cannot be clearly related to a well defined range of values of environmental variables: be it a lack of knowledge or a real datum will be the task of future studies. The waters of the Alps are still relatively unpolluted, but hydraulic stress due to river damming and canalization is a serious problem for macrofauna conservation, and as the glaciers retreat, the species confined to the glacial snouts are at risk of extinction, some of them possibly even before their existence be discovered.

Landscape–stream interactions and habitat conservation for amphibians

Semiaquatic organisms depend on the features of both water bodies and landscapes; the interplay between terrestrial and aquatic systems might influence the semiaquatic communities, determining the scale at which management would be more effective. However, the consequences of such interplay are not frequently quantified, particularly at the community level. We analyzed the distribution of amphibians to evaluate whether the influence of landscape features on freshwater ecosystems can have indirect consequences at both the species and community level. We surveyed 74 streams in northern Italy to obtain data on breeding amphibians, water, and microhabitat features; we also measured features of surrounding landscapes. We used an information-theoretic approach and structural equation models to compare hypotheses on causal relationships between species distribution and variables measured at multiple levels. We also used a constrained redundancy analyses to evaluate causal relationships between multivariate descriptors of habitat features and community composition. Distribution of Salamandra salamandra was related to landscape, hydrological, and water characteristics: salamanders were more frequent in permanent streams with low phosphate concentration within natural landscapes. Water characteristics were dependent on landscape: streams in natural landscapes had less phosphates. Landscape influenced the salamander both directly and indirectly through its influence on phosphates. Community structure was determined by both landscape and water characteristics. Several species were associated with natural landscapes, and with particular water characteristics. Landscape explained a significant proportion of variability of water characteristics; therefore it probably had indirect effects on community. Upland environments play key roles for amphibians, for example, as the habitat of adults, but upland environments also have indirect effects on the aquatic life stages, mediated through their influence on water characteristics. Synergistic effects can magnify the negative consequences of landscape alteration on amphibians; landscape management can be particularly effective, as it can also improve wetland features.

Modelling lake macroinvertebrate species in the shallow sublittoral: relative roles of habitat, lake morphology, aquatic chemistry and sediment composition

Macroinvertebrates are one of the key components of lake ecosystems and are required to be monitored alongside other biological groups to define ecological status according to European Union legislation. Macroinvertebrate communities are highly variable and complex and respond to a diverse series of environmental conditions. The purpose of this study was to examine the relative importance of environmental variables in explaining macroinvertebrate abundance. A total of 45 sub-alpine lakes were sampled for macroinvertebrates in the shallow sublittoral. Environmental variables were grouped into four types: (1) aquatic physical and chemical parameters, (2) littoral and riparian habitat, (3) lake morphometric parameters and (4) sediment chemical characteristics. Nonparametric multiplicative regression (NPMR) was used to model the abundance of individual macroinvertebrate taxa. Significant models were produced for nine out of the 24 taxa examined. Sediment characteristics were the group most frequently included in models and also the factors to which taxa abundance was the most sensitive. Aquatic physical and chemical variables were the next group most frequently included in models although chlorophyll a was not included in any of the models and total phosphorus in only one. This indicates that many taxa may not show a direct easily interpretable response to eutrophication pressure. Lake morphometric factors were included in several of the models although the sensitivity of macroinvertebrate abundance tended to be lower than for sediment and aquatic physical and chemical factors. Habitat factors were only included in three models although riparian vegetation was found to have a significant influence on the abundance of Ephemera danica indicating that ecotone integrity is likely to play a role in its ecology. Overall, the models tended to be specific for species with limited commonality across taxa. Models produced by NPMR indicate that the response of macroinvertebrates to environmental variables can be successfully described but further research is required focussing in more detail on the response of key taxa to relevant environmental parameters and anthropogenic pressures.

The relationship between body size, pupal thoracic horn development and dissolved oxygen in Chironomini (Diptera : Chironomidae)

The aim of this study was to analyze the relationship between the surface development of pupal thoracic horn and adaptation to low oxygen concentration in different species of chironomids. A total of 773 samples of larvae were collected in lakes and streams together with measurements of dissolved oxygen and collection of pu- pal exuviae. The area of the base of the thoracic horn (ring organ, RO) and abdomen length (ABD) of pupae were measured in forty-eight species of Chironomini. RO was signifi cantly correlated with ABD, therefore, the ratio of ring organ/abdomen length (ROA) was calculated to provide a measure less dependent on body size. Chironomus plumosus Linnaeus, Chironomus riparius Meigen and Glyptotendipes pallens (Meigen) had the highest ROA, Mi- crotendipes britteni (Edwards), Paralauterborniella nigrohalteralis (Malloch) and Pseudochironomus prasinatus (Staeger) had the lowest ROA. ROA was still correlated with ABD, so residuals from the regression line (RROA) between RO and ABD were also calculated. An examination of the residuals revealed that some species (C. ripa- rius, Cladopelma virescens (Meigen) and Einfeldia pagana (Meigen)) had a RO larger, whereas other species (M. britteni, P. prasinatus and Stenochironomus gibbus (Fabricius)) had a RO smaller than predicted by regression with ABD. RO was signifi cantly correlated with the 25 th percentile of dissolved oxygen (PCTL) measured in conjunction with benthic macroinvertebrates samples. Hemoglobin concentrations measured in six species were not correlated with ABD and RO, a high hemoglobin content was measured both in small species with a small RO (Polypedilum nubeculosum (Meigen)) and in large species with a large RO (G. pallens). The ring organ is proposed as a morpho- logical trait useful to indicate oxygen concentration in the environment, while other factors such as hemoglobin content are also likely to affect the species ability to respond to oxygen shortage.

The chironomids (Diptera, Chironomidae) from 108 Italian alpine springs.

Chironomids are one of the most abundant and species-rich groups in crenal habitats. Up to 200 species are reported from cold European springs and 73 from Italian Alpine springs, representing about 20 % of the species recorded in Europe and in Italy, respectively (Lindegaard 1995, Crema et al. 1996, Ferrarese 2006, Lencioni 2007). Nevertheless, most crenal systems remain unexplored, and no biotic indexes have been developed to determine their ecological status (Cantonati et al. 2006). We aimed to analyze chironomid taxa distribution in natural or slightly impacted cold springs from an ecological and geographical point of view.

The first record of the subfamily Buchonomyiinae (Diptera, Chironomidae) from Italy

Abstract Mature female pupae and pupal exuviae of Buchonomyia thienemanni were captured from the Taro and Adda rivers in northern Italy in June and July 2002. This is the first record of the subfamily Buchonomyiinae from Italy. The pupae do not substantially differ from those collected in other European localities. New information about the autoecology and geographical distribution of B. thienemanni is given. The species, captured in clean, shallow waters with high oxygen content, is rare in Europe, larvae are known from Ireland only, pupal exuviae from nine countries.

A new benthic quality index for Italian lakes: how to approach with different lake types?

Knowledge about Italian lake macroinvertebrates is still fragmentary. Recently a da ta base referred to 3 7 Italian lakes (591 species: 373 chironomids, 85 oligochaetes, 67 other aquatic insects, 37 mollusks, and 8 crustaceans) was created. Means of percent of oxygen saturation, transparency, and total phosphorus weighted by taxa abundances were calculated to have a benthic quality index weight (BQIW) for each genus and were used to develop a benthic quality index (BQIL) for each site (RosSARO et al. 2006, 2007). This model was not validated because morphometry (volume, depth), conductivity, alkalinity, and pH affected community composition more than oxygen and nutrient concentration. We classified lakes into types according to WFD 2000/60/ CE on the basis of lake altitude, maximum depth, and total surface. Each type was analyzed separately and species assemblages were detected.