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Despite the expected increase in extreme flood frequency, the manner in which terrestrial arthropods cope with regular submersion of their habitat remains poorly understood in meadows, especially in temperate floodplains. Here, we studied the recolonization dynamics of arthropods after a severe spring flood in the Loire Valley (France). We carried out analyses at the community (order or family identification level) and species scales, focusing on the assemblages of two dominant and diverse groups: carabids and spiders. Our objectives were the following: (i) to describe the temporal changes in community structure after flooding and (ii) to assess the influence of landscape configuration on recolonization patterns of species and their functional traits. Fieldwork was performed along three sampling transects, by using 75 pitfall traps, in 2012. A total of 14 767 arthropods belonging to 87 families were trapped, including 5538 spiders (55 species) and 3396 carabids (66 species). Multivariate analyses discriminated assemblages from flooded and non-flooded habitats and revealed changes over time in arthropod families and species after flood withdrawal. In particular, wolf spiders (Lycosidae) were the first to recolonize, whereas other groups clearly avoided flooded sites. Our results also revealed that short distances to hedgerows, and to a lesser extent, distance to woodlands, favoured the recolonization of large and ground-running spiders. In conclusion, our study shows the short-term resilience of certain groups or stenotopic species toflooding and also the relevance of multi-taxon-based studies. The presence of hedgerows has to be considered carefully in management plans because of their role of refuge during flooding. [ABSTRACT FROM AUTHOR]

Aim To assess the exposure of 10 spider species to two drivers of global change (climate and land use), the suitability of the current network of protected areas with respect to this exposure, and the implications for a national conservation programme. Location The western Palearctic and France. Methods We predicted the current and future potential distributions of 10 spider species using species distribution models (SDMs). We explicitly quantified uncertainties in the models and estimated the future environmental suitability with discounted uncertainty. We analysed the predicted future suitability for protected versus unprotected occurrence cells. Results In this first forecast of the future of multiple spider species in the face of environmental changes, we showed that environmental changes could be confidently predicted to have serious impacts on all the studied species, with significant range contractions and expansions within a relatively short time-scale (up to 2050). We predicted that for seven of the 10 species, the current network of protected areas will conserve at least one occurrence cell in suitable conditions in the future. However, we showed that there is considerable room for improvement. Main conclusions This study illustrated how SDMs could be applied to a conservation programme for an understudied taxon such as spiders, in spite of significant uncertainties in their predictions. In addition, the uncertainties raised here compel us to emphasize the pressing need to improve our knowledge on understudied taxa such as spiders. We advocate the necessity of increasing monitoring schemes, experiments and forecasts of environmental change effects on a larger and more diversified range of species than is currently the case in the literature. [ABSTRACT FROM AUTHOR]

Aim To provide a procedure for measuring the rarity of both invertebrate species and assemblages of species from multiple scales without the need for fine-resolution datasets over broad areas. Location The western Palearctic ( WP) and western France. Methods On the basis of different datasets from different geographical extents, we applied a multiscale rarity weight to species occurrence from multiple scales. Multiscale rarity weights were then averaged at an assemblage level in a multiscale index of relative rarity ( IRR). These rarity weights were calculated using a flexible, scale-dependent method that ensures equitable contributions of each scale to the final index. We provided a simple two-scale example of the application, on spiders of western France, for which we obtained occurrence information from a regional-extent dataset (regional scale) and a western Palearctic-extent dataset ( WP scale). Thus, we showed the necessity of a two-scale approach by successively analysing species occurrence, multiscale rarity weights of species and multiscale indices of species assemblage. Finally, we presented a case study within a nature reserve. Results Species occurrences are not predictable from one scale to another, and rarity indices of assemblages are poorly congruent among scales, which supports the necessity of a two-scale approach. Multiscale rarity weights accurately showed information on species rarity from both scales. Multiscale indices of assemblages were congruent but with additional information over each one-scale index. Main conclusions The novelty of the multiscale method developed here is to accurately combine different datasets of varying extents and resolutions to provide multiscale rarity weights for species and indices for assemblages. Given the increasing availability of datasets for invertebrate taxa, this method represents a significant improvement for rarity and conservation studies on invertebrates. [ABSTRACT FROM AUTHOR]

. 1. This study aims to develop a new method for assigning rarity weights to species in evaluations of the relative rarity of arthropod assemblages in conservation/monitoring studies. 2. A flexible characteristic was included in the rarity weighting method by introducing the possibility of fitting the method to a rarity cut-off point defined as the threshold of occurrence below which species are considered as being rare. This allows calculation of a rarity metric (index of relative rarity IRR) with multiple rarity cut-off points. 3. The proposed weighting method was used and compared with three previously proposed methods in a theoretical analysis. IRR values were then calculated for spider assemblages of a National Nature Reserve in France. Two methods of rankings were proposed: a local ranking between sites of the Nature Reserve, and a regional ranking in comparison to a reference database. 4. The proposed weighting method consistently weighted species according to the chosen rarity cut-offs. Species weights were less biased toward common species and rare species weights were less dispersed than with previous methods. Assemblages were consistently ranked according to the rarity of spiders in each assemblage. The index showed different patterns of rarity in assemblages which could not be detected by previous rarity metrics. 5. This method provides an improved understanding of assemblage rarity patterns relative to previous methods and can be consistently applied to other arthropod taxa in other geographic area and/or spatial scales. [ABSTRACT FROM AUTHOR]

The article examines the effects of modified salt-marsh structure on the spider population, particularly on salt exposure and flood resistance. A study was conducted in the salt marshes in Europe, particularly in the Mont Saint-Michel bay in France, where the grass Elymus athericus invaded the marshes. A regression analysis of the soil salinities with respect to the distance from the dike was conducted to determine the relationship between the salt-marsh elevation and its corresponding degree of salinity.