Summary To assess how climate warming, flow regulation and flow restoration affect community dynamics, we analysed long‐term (15–25 years) series of fish community data from four restored and two unrestored reaches of the Rhône River. Environmental variables (low and high flow hydraulics, temperature, sediment flushing operations) were measured in all reaches. Five of the reaches were bypassed by artificial channels, downstream from diversion dams whose construction finished in 1984. Minimum flows in four of these reaches were restored (i.e. increased by factors up to 10) between 2000 and 2006. We examined hypotheses concerning the inter‐annual response of fish community guilds and size structure to flow restoration, climate warming and dam completions. We also performed a principal component analysis (PCA) to explore observed community changes at the river scale (all reaches pooled). We used mixed‐effects linear models to infer potential environmental effects not included in our hypotheses. Our results indicated an inter‐annual effect of flow restoration in the two reaches where minimum flows were most modified (higher percentages of ‘midstream’ species preferring deep and fast water). They also revealed effects of climate warming in the two warmed reaches (higher percentages of southern and small individuals and higher total density). These effects were consistent with our hypotheses. In contrast, dam construction had no consistent effects across reaches. The first PCA axis indicated that the longitudinal organisation of fish communities at the river scale was unchanged, but independent inter‐annual effects of flow restoration and climate change were apparent along the second and third axes. Observed annual variations within sites were weakly related to annual variation in environmental variables. This may be due to the presence of long‐term or time‐lagged environmental effects and the difficulty of estimating community structure of large river fishes accurately enough for this kind of analysis. Fish community responses to flow restoration and other environmental changes may be consistent across multiple reaches when the degree of environmental change is taken into account. Our results support the effectiveness of flow restoration on communities of large rivers subjected to multiple environmental changes.

ABSTRACTAim In times of biodiversity crisis, it is extremely important to understand diversity gradients. In particular, the study of the diversity of ecological functions is a key issue for the management of ecosystem integrity. Here we identify areas of low functional diversity of the native fish fauna in European drainage basins and we determine the relative importance of three underlying mechanisms: environmental filtering, geographic isolation and climatic history.Location The European continent.Methods Based on 14 morphological traits that are closely related to fish function (habitat and dietary niches), three independent functional diversity indices [functional richness (FR), functional evenness (FE), functional divergence (FD)] were calculated for 128 European drainage basins with a total of 230 fish species. The indices were standardized for species richness using null models. The patterns of the standardized indices are described and three potentially underlying mechanisms are tested using variance partitioning and multi‐linear regression models.Results FR and FD were highest in eastern European drainage basins and in Great Britain and lowest in the Mediterranean. FE patterns were less pronounced. All observed patterns were mainly governed by geographic isolation and present environmental conditions. Within the environmental conditions, average annual temperature and precipitation were good predictors for functional diversity. The role of habitat diversity and size was negligible.Main conclusions Geographic isolation coupled with harsh environmental conditions such as extreme temperatures and low precipitation, as in Mediterranean regions, can lead to low FR and FD. This can be explained by extinction that could not be compensated by re‐colonization and high speciation. Due to their high functional redundancy, communities in these areas might better withstand further species extinctions on a small scale. Over the short term, however, their often extremely low FR suggests a less flexible functioning that can hinder their ability to withstand today's rapid environmental and anthropogenic threats.

Launois L, Veslot J, Irz P, Argillier C. Selecting fish‐based metrics responding to human pressures in French natural lakes and reservoirs: towards the development of a fish‐based index (FBI) for French lakes. Ecology of Freshwater Fish 2011: 20: 120–132. © 2010 John Wiley & Sons A/SAbstract – Fish‐based indices of biotic integrity have been developed for many lotic systems but remain scarce for lakes. The goal of this study was to assess the responses of lentic fish assemblages to anthropogenic pressures when environmental variability was controlled for and to compare them between French natural lakes and reservoirs. Environmental features, catchment‐scale anthropogenic descriptors and fish data were collected from 30 natural lakes and 59 reservoirs throughout France. Functional fish metrics were regressed against both anthropogenic variables and the natural environmental conditions. Our results show that fish assemblages are appropriate ecological indicators for both natural and artificial lakes. They underline the necessity to control for the environment when developing indices at broad geographical scales. The relevant metrics differ between natural lakes and reservoirs, which challenges the attempts to use natural systems as references to assess the ecological potential of artificial ones.

The European Water Framework Directive clearly indicates that fish is one of the "quality elements" to be considered for the assessment of lentic systems. However, few fish-based indices (FBIs) of biotic integrity have been developed for lakes so far.Hence, the aim of our study was to develop such a tool for French lakes. Fish surveys, lakes natural environmental parameters, catchment-scale anthropogenic pressures, and local pressures were collected for 67 reservoirs and 24 natural lakes throughout France. After assigning fish species into trophic, reproductive, and tolerance guilds, we derived a set of metrics reflecting complementary aspects of community functioning and condition. Other community-level traits such as richness and evenness were added. These metrics were modeled vs. natural environmental variables and pressures. Reference conditions at each site were then assessed using hindcasting modeling. Separate indices were eventually obtained for natural and artificial lakes by combining selected metrics. Fifteen out of 73 candidate fish metrics, covering all three groups of functional traits, displayed a significant response to anthropogenic pressures. After removal of the redundant traits, the final indices for natural lakes and reservoirs included three and six metrics, respectively. Agricultural-related impacts were prominent for reservoirs, whereas for natural lakes urban and local pressures displayed the most significant effects. (C) 2011 Elsevier Ltd. All rights reserved.

The hawkmoth fauna of La Réunion is largely the result of colonization from Mauritius and Madagascar. These species will have arrived with preadapted ecologies, including larval hostplant preferences. Here we investigate these preferences to determine whether they have been conserved or have adapted to local constraints. Using Factorial Correspondence Analysis (FCA), we compare the hostplant spectra of six widespread, polyphagous species (Acherontia atropos, Agrius convolvuli, Coelonia fulvinotata, Daphnis nerii, Hippotion celerio, H. gracilis) and show that generally they utilize the full spectrum of available plant families, any restriction reflecting absence of particular families from La Réunion rather than specialization. However, although Daphnis nerii is found on several Apocynaceae (Nerium, Ochrosia, Pachypodium, Tabernaemontana) on La Réunion, it seems to avoid the abundant species, Thevetia peruviana. Also, Coelonia fulvinotata seems to have developed an association with the invasive alien, Lantana camara, even though several other potential recorded hostplants also occur on the island. In some instances, absence of records in the region may also be due to a lack of field observations. We also analysed the known global host ranges of all species of the 11 sphingid genera on La Réunion. We found principal hostplant associations are conserved across geographical regions, although there may be local preferences, and that these associations may be taxonomic (Acherontia, Agrius and Coelonia are preferentially associated with Euasterids I) or phytochemical (Nephele densoi, associated with two taxonomically distinct lactiferous families).

Following an up-to-date synopsis on the planthopper fauna and their associated host-plants in the Mascarene Islands including numerous new data, a study of host plant and Fulgoromorpha interaction patterns illustrates some remarkable specificities. The endemic fauna remains essentially on endemic plants and exotic planthoppers have not shifted to them, remaining on exotic plants. Two fulgoromorph families are strictly associated with monocotyledons: (1) the Delphacidae represented by widespread species maintain the same host as the continental source populations, especially exotic Poaceae and (2) the Derbidae which displayed a food conservatism for woody plants are found mostly on endemic Arecaceae, Pandanaceae and Liliaceae. These relationships differ from continental Derbidae, which are recorded as much on dicotyledons as on monocotyledons. Other island specificity appears with the endemic species of Meenoplidae from La Reunion, which are recorded on endemic dicotyledons whereas the continental species are recorded on monocotyledons. In La Reunion, a positive correlation between endemic planthopper diversity recorded on different host plants and endemic plant diversity within different plant orders was observed. This result suggests a stochastic distribution of the planthoppers on the available botanical taxa at the time of colonization. In the Mascarenes, disparities appear between Cixiidae from La Reunion and Mauritius. On the latter, the Cixiidae seem to be mainly monophagous and the majority of them are recorded on Rubiaceae.