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Aquatic life in temporary streams is strongly conditioned by the temporal variability of the hydrological conditions that control the occurrence and connectivity of diverse mesohabitats. In this context, the software TREHS (Temporary Rivers¿ Ecological and Hydrological Status) has been developed, in the framework of the LIFE Trivers project, to help managers for adequately implement the Water Framework Directive in this type of water bodies. TREHS, using the methodology described in Gallart et al (2012), defines six temporal ¿aquatic states¿, based on the hydrological conditions representing different mesohabitats, for a given reach at a particular moment. Nevertheless, hydrological data for assessing the regime of temporary streams are often non-existent or scarce. The scarcity of flow data makes frequently impossible the characterization of temporary streams hydrological regimes and, as a consequence, the selection of the correct periods and methods to determine their ecological status. Because of its qualitative nature, the TREHS approach allows the use of alternative methodologies to assess the regime of temporary streams in the lack of observed flow data. However, to adapt the TREHS to this qualitative data both the temporal scheme (from monthly to seasonal) as well as the number of aquatic states (from 6 to 3) have been modified. Two alternatives complementary methodologies were tested within the TREHS framework to assess the regime of temporary streams: interviews and aerial photographs. All the gauging stations (13) belonging to the Catalan Internal Catchments (NE, Spain) with recurrent zero flows periods were selected to validate both methodologies. On one hand, non-structured interviews were carried out to inhabitants of villages and small towns near the gauging stations. Flow permanence metrics for input into TREHS were drawn from the notes taken during the interviews. On the other hand, the historical series of available aerial photographs (typically 10) were examined. In this case, flow permanence metrics were estimated as the proportion of photographs presenting stream flow. Results indicate that for streams being more than 25% of the time dry, interviews systematically underestimated flow, but the qualitative information given by inhabitants was of great interest to understand river dynamics. On the other hand, the use of aerial photographs gave a good estimation of flow permanence, but the seasonality was conditioned to the capture date of the aerial photographs. For these reasons, we recommend to use both methodologies together.

Functional traits are growing in popularity in modern ecology, but feeding studies remain primarily rooted in a taxonomic-based perspective. However, consumers do not have any reason to select their prey using a taxonomic criterion, and prey assemblages are variable in space and time, which makes taxon-based studies assemblage-specific. To illustrate the benefits of the trait-based approach to assessing food choice, we studied the feeding ecology of the endangered freshwater fish Barbus meridionalis. We hypothesized that B. meridionalis is a selective predator which food choice depends on several prey morphological and behavioral traits, and thus, its top-down pressure may lead to changes in the functional composition of in-stream macroinvertebrate communities. Feeding selectivity was inferred by comparing taxonomic and functional composition (13 traits) between ingested and free-living potential prey using the Jacob's electivity index. Our results showed that the fish diet was influenced by 10 of the 13 traits tested. Barbus meridionalis preferred prey with a potential size of 5-10 mm, with a medium-high drift tendency, and that drift during daylight. Potential prey with no body flexibility, conical shape, concealment traits (presence of nets and/or cases, or patterned coloration), and high aggregation tendency had a low predation risk. Similarly, surface swimmers and interstitial taxa were low vulnerable to predation. Feeding selectivity altered the functional composition of the macroinvertebrate communities. Fish absence favored taxa with weak aggregation tendency, weak flexibility, and a relatively large size (10-20 mm of potential size). Besides, predatory invertebrates may increase in fish absence. In conclusion, our study shows that the incorporation of the trait-based approach in diet studies is a promising avenue to improve our mechanistic understanding of predator-prey interactions and to help predict the ecological outcomes of predator invasions and extinctions.

Temporary streams are those that undergo the recurrent cessation of flow or the complete drying of the stream bed. Although they may represent the main part of the elementary drainage network, or even most of the total network in some areas due to climatic or lithological reasons, temporary streams are rarely included in stream monitoring networks. As a result, hydrological data for assessing the regime of temporary streams are often scarce. The LIFE TRivers project is developing a software (TREHS, Temporary Rivers¿ Ecological and Hydrological Status), which is designed to help the managers for adequately implement the Water Framework Directive in this type of water bodies. The first need for managing a temporary stream is the characterisation of its hydrological regime, in order to help managers selecting appropriate sampling dates and using the right methods to determine its ecological status. Yet, the deviation of the actual regime from the natural one should be determined in order to assess the potential hydrological alteration due to the human activity and thereby determine the `hydrological status¿. TREHS applies a methodology for regime characterisation based on the results of the EU FP7 project MIRAGE. This methodology is based on the assessment of the temporal patterns of six `aquatic states¿ that summarize the transient sets of mesohabitats occurring on a given reach at a particular moment, depending on the hydrological conditions. The qualitative nature of the aquatic states allowed the use of interviews to assess the regime of the streams in the lack of observed flow data. For the questionnaires, the TREHS temporal scheme was simplified from a monthly to a seasonal one and the aquatic states were reduced from six to three (flow, pools and dry). To validate the methodology based on the use of interviews, inhabitants of villages and small towns near to gauging stations were asked to fill the questionnaire. The preliminary results on temporary stream regimes derived from interviews were rather consistent with those obtained from discharge data. However, two main sources of uncertainty were found; one was due to disparate responses to questionnaires done at the same river reach, and the other was related to the low accuracy of gauging stations for detecting flow cessation.

This study aimed to describe patterns of diversity of Baetidae (Ephemeroptera) at the ommunity and population levels within the Montseny Mountain range (North-East Iberian Peninsula). We studied both the distribution of 4 species of baetids in 20 sites among three catchments along the altitudinal gradient (350-1700 masl); and the genetic diversity of the mtDNA cytochrome c oxidase subunit I (cox1) gene of the two common species Baetis alpinus and Baetis rhodani. We found a gradual replacement of the dominant species along the altitudinal gradient. Baetis alpinus inhabited sites at high-altitudes, and this species was replaced by B. rhodani when the altitude decreased. Baetis melanonyx and Alainites muticus attained low abundance at all river sections, and no clear altitudinal trend appeared. Our hypothesis at the population level was that genetic structuring is associated with geographic distance and limited by drainage boundaries among the three studied catchments because of the short-time dispersion of adults. Unexpectedly, analyses of molecular variance (AMOVA) and isolation-bydistance (IBD) showed genetic diversity was unstructured by distance for both species, which may be explained by the relatively short spatial scale studied and small topographic barriers among the three catchments. The Generalized Mixed Yule-Coalescent (GMYC) model showed that B. rhodani had two differentiated genetic lineages that co-occurred in all sites. Overall, diversity of baetids was structured at the community level along the altitudinal gradient, whereas it was unstructured at the population level within the Montseny Mountain range.

24 páginas, 7 figuras, 5 tablas., 1. Species assemblages of diatoms, rotifers, chydorids, planktonic crustaceans and chironomids were studied in 235 alpine lakes in the Alps, Pyrenees, Tatras (Western Carpathians), Retezat (Southern Carpathians) and Rila Mountains (Balkans). 2. For all taxonomic groups we found a hierarchical structure in the community assemblage using distinct scales of lake clustering (number of k-means groups) based on species composition similarity (Hellinger distance). We determined the optimal partition in assemblage types (i.e. number of lake clusters) for each taxonomic group by maximising the sum of the taxon indicative value (IndVal) and performed discriminant analyses, using environmental variables not conditioned by geographical patterns. Relevant environmental variables differed among and within taxonomic groups. Therefore the assemblages respond to a complex environmental mosaic, with the exception of diatom assemblages, which followed an acid–base gradient. 3. The significant environmental variables could be grouped into four general factors: lake size, tropho-dynamic status, acid–base balance and ice-cover duration (i.e., altitudinal gradient). Lake size was significant for the highest number of assemblage types; however, the most significant factor differed among taxonomic groups: acid–base balance for diatoms, lake size for rotifers, ice-cover duration for chydorids and planktonic crustaceans and tropho-dynamic status for chironomids. No single environmental typology accounted for the assemblage structure of all taxonomic groups. 4. However, defining ecological thresholds as values within environmental gradients at which the rate of change in assemblages is accelerated relative to points distant from that threshold, we were able to find specific threshold values for each of the four main general environmental factors identified, which were relevant across several taxonomic groups: 3 ha for lake area; 0.6 mg L−1 for dissolved organic carbon; 190 days for ice-cover duration and 200 μeq L−1 for acid neutralising capacity. Above and below these values ecosystem organisation change substantially. They have direct applications in establishing lake typologies for environmental quality and biodiversity conservation programmes, and in improving predictions about global change impacts., The financial support from the EU projects EUROLIMPACS (GOCE-CT-2003-505540) and EMERGE (EVK1-CT-1999-00032) is acknowledged. This is a GRACCIE (CSD2007-00067) contribution.

Macroinvertebrates associated to reed-beds (Phragmites australis) in six shallow natural water bodies along the 220 km of coast of the Comunidad Valenciana (Spain) were studied. These sites were selected to reflect different trophic states, but also, and due to the natural variability of mediterranean wetlands, they greatly differ in salinity and hydroperiod. To unify the sampling, reed bed was chosen to provide data from a habitat common to all wetlands, including the most eutrophic ones where submerged macrophytes have disappeared due to water turbidity. Individual submerged stems of Phragmites australis were sampled along with the surrounding water. The animal density found refers to the available stem surface area for colonization. Forty-one taxa were recorded in total, finding Chironomidae to be the most important group, quantitatively and qualitatively. In freshwater sites it was observed an increase in macroinvertebrate's density at higher trophic states. Nevertheless each studied region had a different fauna. The PCA analysis with macroinvertebrate groups distinguished three types of environment: freshwaters (characterized by swimming insect larvae, collectors and predators, oligochaetes and Orthocladiinae), saline waters (characterized by crustaceans and Chironominae) and the spring pool, which shares both taxa. Chironomids were paid special attention for being the most abundant. A DCA analysis based on the relative abundance of Chironomids reveals salinity as the main characteristic responsible for its distribution, but trophic state and hydrological regime were also shown to be important factors. Se han estudiado los macroinvertebrados asociados a la vegetación de carrizo (Phragmites australis) en seis lagunas someras a lo largo de los 220 km de costa de la Comunidad Valenciana (España). Las lagunas se eligieron de manera que se contemplasen diferentes estados tróficos, pero además y reflejando la natural variabilidad de los humedales mediterráneos, presentan importantes diferencias en cuanto al hidroperiodo y la salinidad. Para unificar el muestreo, se eligió el carrizo por ser un elemento común en todos los humedales, incluso los más eutróficos en los que los macrófitos sumergidos han desaparecido debido a la turbidez del agua. Para cada muestra se toma individualmente la parte sumergida de una planta de Phragmites australis junto con el agua circundante. La densidad de animales encontrados se refiere a superficie colonizable del tallo de la planta. En total se han encontrado 41 taxones, siendo Chironomiidae el grupo más importante tanto cuantitativa como cualitativamente. En las lagunas de agua dulce, se observó un aumento de la densidad de macroinvertebrados en los niveles tróficos mayores. Sin embargo cada zona de estudio tiene una fauna diferente. El análisis PCA de los grupos de macroinvertebrados diferencia tres tipos de ambientes: aguas dulces (caracterizados por larvas nadadoras de insectos recolectores y depredadores, oligoquetos y orthocladinos), aguas salobres (caracterizadas por la presencia de crustáceos y Chironomiinae) y el "ullal" o surgencia de agua que comparte taxones de los dos grupos anteriores. Se ha prestado especial atención al grupo de quironómidos por ser los más abundantes. Un análisis DCA basado en la abundancia relativa de las especies de quironómidos, muestra la salinidad como la principal característica responsable de su distribución, siendo luego el estado trófico y el régimen hidrológico factores también importantes.