Iraima Verkaik

Identification of material obtained in various bee surveys at several sites across Catalonia (NE Spain) has revealed the occurrence of two species of Megachile previously unrecorded from the Iberian Peninsula: Megachile (Megachile) alpicola and Megachile (Eutricharaea) flabellipes. A third species, Megachile (Megachile) lapponica, is recorded for the second time in the Iberian Peninsula. We provide a map of the known distribution in Catalonia and information on floral records for the three species.

The overall purpose of this study was to assess the knowledge that students have about the ecosystem concept of rivers and their sustainable management. A survey of nine questions gathered responses from 3447 students at three different Spanish education levels (Primary, Secondary, and bachelor’s degree in Primary Education) and six different geographic territories in the Iberian Peninsula. Respondents showed a limited understanding of rivers, much simpler than the ecosystem concept, which was related to proposals of unsustainable management of these ecosystems. Although the results were analogous among territories, undergraduate students had a more complex concept of rivers as well as more sustainable ideas regarding their management compared with Primary and Secondary Education students. This study demonstrates the lack of knowledge transfer between science and students regarding river ecosystems. Current educational programs should be adapted to address, even at early stages of education, the sustainability challenges around river ecosystems.

Aim: To analyse temporal metacommunity dynamics in river networks in relation to hydrological conditions and dispersal.Location: Fifteen river reaches from the Llobregat, Besòs and Foix catchments in the North‐Eastern Iberian Peninsula.Taxon: Aquatic macroinvertebrates belonging to 99 different families.Methods: We sampled aquatic macroinvertebrate communities during spring in 20 consecutive years. We built two environmental distances (one related with water chemistry and another one with river flow regime) and two spatial distances (network distance and topographic distance). Then we used Mantel tests (accounting for spatial autocorrelation) to relate macroinvertebrate dissimilarity with environmental and spatial distances. Additionally, we determined the dry and wet years using the Standardized Precipitation Index (SPI) and we classified macroinvertebrate families based on their ability to fly and to drift. Finally, we ran a linear regression model including the correlation value (r) of each Mantel test as response variable and distance type (environmental or spatial), SPI, dispersal mode, their pairwise interactions and a three‐way interaction as predictor variables.Results: Metacommunity organization varied over time and it was significantly affected by precipitation, which can be related to river network connectivity. The environmental filters, mainly the flow regime, were generally more important than the spatial filters in explaining community dissimilarity over the study period. However, this depended on the dispersal abilities of the organisms. Network fragmentation due to flow intermittence during the dry years significantly reduced the dispersal capacity of strong aerial dispersers, leading to spatially structured metacommunities. For strong drift dispersers, community dissimilarity patterns were generally best explained by environmental filters regardless of SPI.Main conclusions: A significant temporal variation in metacommunity organization can be expected in highly dynamic systems (e.g. Mediterranean rivers) and it might depend on the dispersal modes and abilities of the organisms, since they determine the response to changes in environmental and landscape filters.

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 fishBarbus meridionalis. We hypothesized thatB. meridionalisis 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 meridionalispreferred 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.

Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators’ extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1) leads to a ‘mesopredator release’, affects primary consumers and changes whole community structures, and (2) triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the top-down effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel), conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire. We found that top predator absence led to ‘mesopredator release’, and also to ‘prey release’ despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem’s structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers’ extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been extirpated, to restore ecosystem structure and function.

Bushfires occur in most environments in Australia and yet there are few studies about fire effects on aquatic ecosystems. To study the effects of fire on aquatic macroinvertebrates we sampled three streams in burnt catchments (i.e. burnt) and three streams in unburnt catchments (i.e. control), nine months after severe bushfires in northern Victoria. The sampling period coincided with a severe and prolonged period of drought – during the 8th year of a series of thirteen consecutive years of below average rainfall. There was a significant effect of bushfire on macroinvertebrate richness, composition and function. At the burnt sites, there was lower taxon richness but a 4-fold increase in abundance, which was mainly to the result of increases in taxa such as Chironomidae, Simuliidae, Dinotoperla sp. and Taschorema sp. A higher percentage of gathering collectors was found at the burnt sites, whereas scrapers and shredders were co-dominant in the control streams. The responses of the macroinvertebrates may have been impaired by post-fire persistence of low flows associated with the continuing drought, in comparison with the rapid recovery of the catchment overstorey vegetation (Eucalyptus spp.). The consequences of the megadrought combined with catchment bushfires, have no doubt reduced the resilience of the macroinvertebrate communities.

Mediterranean climate ecosystems are characterised by frequent fires, but few studies have focused on the effects of fire disturbance on biological communities in streams in these ecosystems. To compare the responses of macroinvertebrate communities to wildfire, eight sites were established and annually sampled for 5 years. Two months after fire, the number and abundance of macroinvertebrate taxa were not significantly different from those in control streams, but their composition and functional attributes had changed. As expected, an increase in r‐strategy taxa was observed during the year following fire. Above all, macroinvertebrate assemblages responded more strongly to hydrology (previous spring precipitation) than to fire. Drought was found to be an overriding disturbance factor, but macroinvertebrate assemblages showed high resilience. In a climate change scenario coupled with human demand for water, it will be important to study the effects of drought interacting with other disturbances like wildfire (which is in turn driven by drought).