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Tropical rainforests are one of the most diverse ecosystems worldwide, yet the mechanisms driving the spatial distribution of their biodiversity remain poorly understood. Here, we tested the effects of elevation, sampling method and their interaction on α and β diversities of spider assemblages between two close elevations in one tropical forest of French Guiana. Through a standardized protocol, both ground- and vegetation-dwelling (up to 2.5-m high) assemblages were sampled at medium and high elevations, during day and night using 3 complementary methods (beating, sweeping, and nocturnal hand collecting). Despite a lower total number of species at high elevation, we found no significant effect of elevation on mean species richness. However, elevation had a significant effect on species composition, notably with less web builders and more ground hunters at higher elevations. In addition, we found a significant effect of sampling methods on both estimated species richness and composition. These results suggest that even slight elevation shape spider assemblages of tropical forests, which probably contributes to the high turn-over and amazing gamma diversity of these ecosystems. [ABSTRACT FROM AUTHOR]

Urbanisation is an ongoing process associated with multiple environmental changes affecting ecosystems worldwide. Temperature and habitat are main drivers of animal communities within cities, but quantifying their relative weights remains a challenge, as urban heat islands (UHI) often co-vary with land-cover. This study aims to disentangle the effects and relevant scale of temperature and habitat on ground-dwelling spider communities. Based on an original sampling design, we collected 20,761 spider individuals belonging to 137 species at 36 sampling sites in the city of Rennes (northwest France). We characterised communities by assessing the number of trapped individuals at each site, as well as calculating several metrics to estimate taxonomic and functional diversities. Temperature metrics were obtained from two sensor networks monitoring UHI (100-m resolution) and near-ground temperature (1-m resolution) independently. Land-cover and isolation were used to describe landscapes, and vegetation structure to describe local habitats. We used generalized linear mixed models to disentangle the effects of temperature from those of habitat at the landscape and local scales, and identified relationships between community descriptors and predictors. We show that temperature-related metrics are important predictors of spider communities, and that the landscape and local scales have independent effects. Near-ground temperature alone explained 24% of the number of trapped individuals, whereas UHI explained 20% of taxonomic diversity. Local vegetation height and cover were significant predictors of functional diversity, and explained 22% and 25% of variance, respectively. We conclude that locally applied planning measures could mitigate the loss of taxonomic diversity induced by the atmospheric UHI and promote the establishment of more diverse communities. [ABSTRACT FROM AUTHOR]

In the past decade, environmental DNA (eDNA) assays have become an essential tool to investigate species presence with samples from the environment instead of collected specimens. eDNA sampling techniques have proved their worth in freshwater and marine studies; now, some trends emerge for their use in terrestrial habitats and particularly to study arthropods. After a systematic review of the literature, we illustrate and analyse the diversity of such studies and discuss their benefits and drawbacks.We identified the most relevant research themes and focused on (i) the taxa and environmental sample types targeted and (ii) the details of the survey scheme. In parallel, we also assessed the available number of sequences from cytochrome c oxidase subunit I (COI), 16S and 18S barcode regions for four major taxa (spiders, centipedes, springtails and insects) in relation to their diversity.We found strong taxonomic and geographic biases regarding coverage per barcode. eDNA research on terrestrial arthropods mainly focuses on insect species that affect humanity in a positive or negative way, and the availability of sequences is much higher for species from temperate‐developed countries than from tropical ones. Moreover, although a high variety of environmental samples are being used, most studies do not assess the barcode completeness of the target taxa nor compare the efficacy of eDNA monitoring technique to other well established and known traditional techniques.Careful workflow designs and comparisons are needed before giving any management or conservation advice as eDNA monitoring does not come without error. Strengths and weaknesses of eDNA assays for conservation are discussed. [ABSTRACT FROM AUTHOR]

Copyright of Entomologia Experimentalis et Applicata is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Holarctic species offer great opportunities to study biogeography, phylogenetics, taxonomy, and local adaptation. Species that are considered conspecific between the Palearctic and the Nearctic realms are often split into 2 or more species when denser sampling and molecular markers are applied. Similar in complexity but at a finer geographical scale are species groups having Arctic-Alpine distributions where lineages have complicated demographic histories due to glacial dynamics. In both cases, allopatric speciation might not result in fast differentiation of morphological characters if environmental conditions in isolated areas are similar and the main driver of variability is genetic drift. Here, we study the Holarctic Pardosa hyperborea (Thorell, 1872) and its closest European relatives to assess their taxonomic status and patterns of genetic variability. Based on DNA barcodes and genomic data from double-digest restriction site associated sequencing, we propose that the North American populations should be regarded as a distinct species (P. luteola Emerton,1894, stat. resurr.), possibly consisting of several independent lineages. With the help of D-statistics, population genetic simulations and phylogenetic networks analysis, we demonstrate historical introgression among European species of the group and a likely explanation for shared DNA barcodes among allopatric and fully differentiated species. Our study exposes a promising model for studying speciation processes and demographic history in parallel on both sides of the Atlantic Ocean and demonstrates the usefulness of genomic tools in elucidating the taxonomy and biogeography of taxa across broad geographic scales. [ABSTRACT FROM AUTHOR]

A new species of Hypaeus Simon 1900 is described from French Guiana based on both sexes, Hypaeus olympeaesp. nov. We employed morphological evidence, field observation, as well as the mitochondrial COI rapidly evolving loci to confirm that both males and females belong to the same species. Finally, nine species are newly recorded for the salticid fauna of French Guiana, Cyllodania fasciata (Caporicaco, 1954) syn. nov. is considered junior synonym of Gypogyna forceps Simon, 1900 and 12 COI sequences corresponding to four previously unsequenced Hypaeus species are added to GenBank. [ABSTRACT FROM AUTHOR]

There is a secret pleasure in naming new species. Besides traditional etymologies recalling the sampling locality, habitat or morphology of the species, names may be tributes to some meaningful person, pop culture references and even exercises of enigmatography. Using a dataset of 48 464 spider etymologies, we tested the hypothesis that species names given by taxonomists are deeply influenced by their cultural background. Specifically, we asked whether naming practices change through space or have changed through time. In absolute terms, etymologies referring to morphology were the most frequently used. In relative terms, references to morphology peaked in 1850–1900 and then began to decline, with a parallel increase in etymologies dedicated to people and geography. We also observed a dramatic increase in etymologies referring to pop culture and other cultural aspects in 2000–2020, especially in Europe and the Americas. While such fashionable names often carry no biological information regarding the species itself, they help give visibility to taxonomy, a discipline currently facing a profound crisis in academia. Taxonomy is among the most unchanged disciplines across the last centuries in terms of tools, rules and writing style. Yet, our analysis suggests that taxonomists remain deeply influenced by their living time and space. [ABSTRACT FROM AUTHOR]

Dispersal and its evolution play a key role for population persistence in fragmented landscapes where habitat loss and fragmentation increase the cost of between-habitat movements. In such contexts, it is important to know how variation in dispersal and other traits is structured, and whether responses to landscape fragmentation are aligned with underlying dispersal-trait correlations, or dispersal syndromes. We, therefore, studied trait variation in Erigone longipalpis , a European spider species specialist of (often patchy) salt marshes. We collected spiders in two salt-marsh landscapes differing in habitat availability. We then reared lab-born spiders for two generations in controlled conditions, and measured dispersal and its association with various key traits. Erigone longipalpis population densities were lower in the more fragmented landscape. Despite this, we found no evidence of differences in dispersal, or any other trait we studied, between the two landscapes. While a dispersal syndrome was present at the among-individual level (dispersers were more fecund and faster growing, among others), there was no indication it was genetically driven: among-family differences in dispersal were not correlated with differences in other traits. Instead, we showed that the observed phenotypic covariations were mostly due to within-family correlations. We hypothesize that the dispersal syndrome is the result of asymmetric food access among siblings, leading to variation in development rates and carrying over to adult traits. Our results show we need to better understand the sources of dispersal variation and syndromes, especially when dispersal may evolve rapidly in response to environmental change. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Applied Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dispersal abilities are important to support metapopulation functioning and species distributions, yet it is rarely accounted for in conservation. Here, we compared the propensity for dispersal between the two fishing spiders present in Europe: the widespread habitat‐generalist Dolomedes fimbriatus and the scarcer red‐listed Dolomedes plantarius.We experimentally tested for airborne and waterborne dispersal using first instar juveniles sampled in nursery webs, and older juveniles. We estimated the propensity for short and long‐distance dispersal of airborne and waterborne behaviours, and we tested the difference between species with generalised linear mixed models.Airborne (ballooning) and waterborne (sailing) behaviours were more frequent for D. fimbriatus than for D. plantarius, indicating a higher propensity of the former for long‐distance dispersal.The frequency of rappelling behaviour, and thus the propensity for short‐distance dispersal, did not differ between species. However, we found contrasting results for short‐distance dispersal on the water, with rowing being more frequent and running less frequent for D. plantarius than for D. fimbriatus.The different propensity for dispersal between the two species might be partly explained by the ecology of D. plantarius, which is known to be more habitat‐specialist and more dependent to water bodies than D. fimbriatus.The limited propensity for dispersal of the red‐listed D. plantarius is another argument for conserving an interconnected network of wetlands in Fennoscandia. Indeed, increased isolation of populations would be detrimental for species maintenance. [ABSTRACT FROM AUTHOR]

The fall armyworm, Spodoptera frugiperda, (hereafter FAW) is a major pest in South American crops; however, knowledge about its potential native natural predators is limited. Size is a factor that constrains predators against prey, such as larvae of varying sizes. The predation capability of males and females of the native wolf spiders Lycosa thorelli and Pavocosa sp. were evaluated against different-sized FAW larvae. Contrary to expected results, both sexes consumed FAW larvae of similar size ranges. L. thorelli captured larger FAW larvae, suggesting this species might prey on a wider range of FAW instars indicating its potential role as a FAW biological control agent. [ABSTRACT FROM AUTHOR]

The Arctic tundra is characterised by harsh conditions and environmental gradients are especially pronounced. Variation in functional traits along such gradients provide insights into the drivers of species abundance and distribution and are particularly valuable in this region currently experiencing strong climate warming. Over three consecutive years, we analysed the interacting effect of two environmental factors, habitat and elevation, on the abundance, body size, and clutch size in two common Low-Arctic invertebrate predators (Lycosidae, Araneae), Pardosa furcifera (Thorell 1875) and Pardosa hyperborea (Thorell 1872). Using generalised linear models, we firstly showed a habitat partitioning between P. furcifera, which dominated wet habitats, like fens, and P. hyperborea, which was more associated with drier habitats, like shrubs. Secondly, we found smaller body sizes at high elevation in P. hyperborea, a species that has a southern distribution in Greenland, and we identified season length as a major driver of the development in this species. In P. furcifera, a species likely more cold adapted, we found no body size difference between elevations, suggesting that local conditions (e.g. prey availability or snowmelt timing) are more important in explaining body size variations. Finally, body size and clutch size were strongly correlated in both species, but clutch size was not affected by habitat or elevation. We argue that fecundity is likely influenced by trade-offs and that considering additional complementary trait measurements would allow for a better understanding of the mechanisms underlying patterns in species life-history traits along environmental gradients. [ABSTRACT FROM AUTHOR]

Large quantities of Pacific oyster and blue mussel shells are deposited along the shore of Mont-Saint-Michel Bay in western France as waste from aquaculture operations. These shell beds have become integrated into the salt marsh vegetation over time and provide a habitat for an endangered wolf spider species. The spiders use the shells as a refuge and breeding habitat, hiding during the day and hunting at night. While the importance of anthropogenic resource subsidies for predatory spiders is known, documented examples in the scientific literature are rare. [Extracted from the article]

Shrub communities often modify understory soil and vegetation characteristics. However, the effect of individual shrubs on the soil seed bank (y6SSB) could be variable in grasslands depending on the presence of grazing. We examined how grazing influences patch-level effects of shrubs on local soil seed bank (SSB) density, species richness, and composition. Twenty individuals of Crataegus pseudomelanocarpa (dominant woody species in the study area) were randomly selected in the degraded ecotone between forest and grassland in northern Iran, 10 in grazed and 10 in ungrazed areas. Soil samples were collected under shrubs and the space between shrubs and then transported to the greenhouse. The seedling emergence method was used to estimate SSB density and composition in the greenhouse. In total, 61 species germinated from the soil samples with 47 species in the grazed sites (43 species in shrub, 34 species in open) and 54 species in the ungrazed sites (43 species in shrub, 46 species in open). SSB density and richness were significantly lower under shrubs compared with outside in the ungrazed areas while the converse results were found in the grazed areas. Although grazing decreased SSB density and species richness, this decrease was less pronounced under the shrubs, indicating the nursing roles of shrubs against grazing on seed production by herbaceous plants. [ABSTRACT FROM AUTHOR]

Changing abiotic conditions can affect the phenology of animals and plants with implications for their reproductive output, especially in rapidly changing regions like the Arctic. For instance in arthropods, it was recently shown that females of the spider species Pardosa glacialis (Thorell 1872) (Lycosidae) are able to produce two clutches within one growing season in years when snowmelt occurs particularly early. This phenomenon could be widespread in northern latitudes, and here we investigated the voltinism of two other very abundant species of wolf spiders in the Low-Arctic, Pardosa hyperborea (Thorell 1872) and Pardosa furcifera (Thorell 1875), over the period 2015–2017. Whilst a bimodal pattern in the clutch size frequency distribution was only revealed for P. hyperborea, we were able to show that both species can produce a second clutch over the active season by using information on the embryonic stages. We also observed significantly larger first than second clutches. We argue that information about the embryonic stage can be critical for evaluating evidence of wolf spider populations producing more than one clutch in a season. Our study provides evidence that bivoltinism could be a more widespread pattern than expected in Arctic wolf spiders. It remains to be investigated what the trophic consequences of such patterns are in a global warming context. We thus highlight the need for a coordinated framework for such further studies, integrating and relating various functional traits. [ABSTRACT FROM AUTHOR]

Aim: Species distribution models (SDMs) have emerged as essential tools in the equipment of many ecologists, useful to explore species distributions in space and time and answering an assortment of questions related to biogeography, climate change biology and conservation biology. Historically, most SDM research concentrated on well‐known organisms, especially vertebrates. In recent years, these tools are becoming increasingly important for predicting the distribution of understudied invertebrate taxa. Here, we reviewed the literature published on main terrestrial arthropod predators (ants, ground beetles and spiders) to explore some of the challenges and opportunities of species distribution modelling in mega‐diverse arthropod groups. Location: Global. Methods: Systematic mapping of the literature and bibliometric analysis. Results: Most SDM studies of animals to date have focused either on broad samples of vertebrates or on arthropod species that are charismatic (e.g. butterflies) or economically important (e.g. vectors of disease, crop pests and pollinators). We show that the use of SDMs to map the geography of terrestrial arthropod predators is a nascent phenomenon, with a near‐exponential growth in the number of studies over the past ten years and still limited collaborative networks among researchers. There is a bias in studies towards charismatic species and geographical areas that hold lower levels of diversity but greater availability of data, such as Europe and North America. Conclusions: Arthropods pose particular modelling challenges that add to the ones already present for vertebrates, but they should also offer opportunities for future SDM research as data and new methods are made available. To overcome data limitations, we illustrate the potential of modern data sources and new modelling approaches. We discuss areas of research where SDMs may be combined with dispersal models and increasingly available phylogenetic and functional data to understand evolutionary changes in ranges and range‐limiting traits over past and contemporary time‐scales. [ABSTRACT FROM AUTHOR]

Although functional and phylogenetic diversities are increasingly used in ecology for a variety of purposes, their relationship remains unclear, and this relationship likely differs among taxa, yet most recent studies focused on plants. We hypothesize that communities may be diverse in functional traits due to presence of: many phylogenetic lineages, trait divergence within lineages, many species and random functional variation among species, weak filtering of traits in favorable environments, or strong trait divergence in unfavorable environments. We tested these predictions for taxa showing higher (ants), or lower (spiders, ground beetles) degrees of competition and niche construction, both of which might decouple functional traits from phylogenetic position or from the environment. Studying > 11,000 individuals and 216 species from coastal heathlands, we estimated functional as minimum spanning trees using traits related to the morphology, feeding habits and dispersal, respectively. Relationships between functional and phylogenetic diversities were overall positive and strong. In ants, this relationship disappeared after accounting for taxonomic diversities and environments, whereas in beetles and spiders taxonomic diversity is related to functional diversity only via increasing phylogenetic diversity. Environmental constraints reduced functional diversity in ants, but affected functional diversity only indirectly via phylogenetic diversity (ground beetles) and taxonomic and then phylogenetic diversity (spiders and ground beetles). Results are consistent with phylogenetic conservatism in traits in spiders and ground beetles. In ants, in contrast, traits appear more phylogenetically neutral with any new species potentially representing a new trait state, tentatively suggesting that competition or niche construction might decouple phylogenetics from trait diversity. [ABSTRACT FROM AUTHOR]

Most species encounter large variations in abiotic conditions along their distribution range. The physiological responses of most terrestrial ectotherms (such as insects and spiders) to clinal gradients of climate, and in particular gradients of temperature, can be the product of both phenotypic plasticity and local adaptation. This study aimed to determine how the biogeographic position of populations and the body size of individuals set the limits of cold (freezing) resistance of Dolomedes fimbriatus. We compared D. fimbriatus to its sister species Dolomedes plantarius under harsher climatic conditions in their distribution range. Using an ad hoc design, we sampled individuals from four populations of Dolomedes fimbriatus originating from contrasting climatic areas (temperate and continental climate) and one population of the sister species D. plantarius from continental climate, and compared their supercooling ability as an indicator of cold resistance. Results for D. fimbriatus indicated that spiders from northern (continental) populations had higher cold resistance than spiders from southern (temperate) populations. Larger spiders had a lower supercooling ability in northern populations. The red‐listed and rarest D. plantarius was slightly less cold tolerant than the more common D. fimbriatus, and this might be of importance in a context of climate change that could imply colder overwintering habitats in the north due to reduced snow cover protection. The lowest cold resistance might put D. plantarius at risk of extinction in the future, and this should be considered in conservation plan. [ABSTRACT FROM AUTHOR]

Conservative biological control promotes the use of native natural enemies to limit the size and growth of pest populations. Although spiders constitute one of the most important groups of native predators in several crops, their trophic ecology remains largely unknown, especially for several generalist taxa. In laboratory, we assessed the predatory behaviour of a wandering spider (the wolf spider Lycosa thorelli (Keyserling, 1877) against several arthropods varying in size and trophic positions, all found in South American soybean and rice crops. As prey we used the bug Piezodorus guildinii (Westwood, 1837) as well as larvae and adults of the moth Spodoptera frugiperda (Smith, 1797), both being considered important pests in Uruguayan crops. We also used several non‐pest arthropods as prey, sarcophagid flies, carabid beetles and wolf spiders. All prey were attacked in more or less high, although not statistically differing, proportions. However, carabids were not consumed, and bugs were consumed in significantly lower proportions than flies. A negative correlation was found between prey size and acceptance rate. Immobilization times were longer against larvae when compared to moths and flies, while predatory sequences were longer for bugs when compared to flies, moths and spiders. In addition, we found a positive effect of prey size on predatory sequence length and complexity. Our results confirm the ability of spiders to attack and feed upon prey with different morphologies, included well‐defended arthropods, and their potential use as natural enemies of several pests in South American crops. [ABSTRACT FROM AUTHOR]

Although species delimitation is often controversial, emerging DNA-based and classical morphology-based methods are rarely compared using large-scale samplings, even less in the case of widely distributed species that have distant, allopatric populations. In the current study, we examined species boundaries within two wolf spider species of the genus Pardosa (Araneae, Lycosidae), P. riparia and P. palustris. Wolf spiders constitute an excellent model for testing the relevance of traditional vs. modern methods in species and population delimitation because several closely related species are distributed over cross-continental geographic ranges. Allopatric populations of the two Pardosa species were sampled across Europe to Far East Russia (latitudinal range > 150°) and several dozen individuals were studied using morphological characters (morphometry of three measures for both sexes, plus five in males only and two in females only), DNA barcoding (COI sequencing) and double-digest restriction site associated DNA sequencing (ddRADseq). The results obtained allow for changing the taxonomic status of two Far East Russian populations to subspecies and ddRADseq proved to be a powerful tool for taxonomic research despite scarce sampling and inherent subjectivity of species delimitation in allopatry. Overall, this study pleads for both multi-criteria and more population-based studies in taxonomy. [ABSTRACT FROM AUTHOR]

High diversity in tropical compared to temperate regions has long intrigued ecologists, especially for highly speciose taxa like terrestrial arthropods in tropical rainforests. Previous studies showed that arthropod herbivores account for much tropical diversity, yet differences in the diversity of predatory arthropods between tropical and temperate systems have not been properly quantified. Here, we present the first standardized tropical–temperate forest quantification of spider diversities, a dominant and mega‐diverse taxon of generalist predators. Spider assemblages were collected using a spatially replicated protocol including two standardized sampling methods (vegetation sweep netting and beating). Fieldwork took place between 2010 and 2015 in metropolitan (Brittany) and overseas (French Guiana) French territories. We found no significant difference in functional diversity based on hunting guilds between temperate and tropical forests, while species richness was 13–82 times higher in tropical versus temperate forests. Evenness was also higher, with tropical assemblages up to 55 times more even than assemblages in temperate forests. These differences in diversity far surpass previous estimates and exceed tropical–temperate ratios for herbivorous taxa. [ABSTRACT FROM AUTHOR]

We assessed how assemblages of spiders were structured in small Hawaiian tropical forest fragments (Hawaiian, kipuka) within a matrix of previous lava flows, over both space (sampling kipuka of different sizes) and time (comparison with a similar study from 1998). Standardized hand-collection by night was carried out in May 2016. In total, 702 spiders were collected, representing 6 families and 25 (morpho-)species. We found that the number of individuals, but not species richness, was highly correlated with the area of sampled forest fragments, suggesting that kipuka act as separate habitat islands for these predatory arthropods. Species richness was significantly lower in the lava matrix outside the kipuka compared to the kipuka habitats, although there was no statistical difference in species composition between the two habitats, largely because of similarity of non-native species in both habitats. Over the last 20 years, the abundance of non-native spider species substantially increased in both kipuka and lava habitats, in marked contrast to the vegetation that has remained more intact. With endemicity of terrestrial arthropods reaching over 95% in native forests, non-native predatory species present a critical challenge to the endemic fauna. [ABSTRACT FROM AUTHOR]

Assessment of habitat restoration often rely on single-taxa approach, plants being widely used. Arthropods might yet complement such evaluation, especially in hard, poorly-diversified environments such as maritime clifftops. In this study we compared the responses of spiders and plants (both at species and assemblage levels) to increasing time of heathland restoration. Sampling took place in different sites of Brittany (Western France), using a replicated design of both pitfall traps and phytosociological relevés. A total of 5056 spiders belonging to 160 species, and 103 plant species were found. No change in species richness between degradation states was found for spiders. Plant species richness was lower in highly degraded habitats of recently restored sites but was not in the oldest restored one. Species composition greatly changed through turnover mechanisms between all sites and degradation states, for both spider and vegetation. Heterogeneity was higher in references states, and increased over restoration time between sites. The number of indicator species decreased with restoration age for spiders, while no indicator species was found for plants. Restoration is still on-going after 15 years, with no recovery of reference assemblages for both plants and spiders, but there were some signals toward reference in the oldest restoration site. Plants and spiders were proved to be complementary bio-indicators of post disturbance restoration, as they bring different, scale-dependent information on restoration success. [ABSTRACT FROM AUTHOR]

While many arthropod species are known to depend, directly or indirectly, on certain plant species or communities, it remains unclear to what extent vegetation shapes spider assemblages. In this study, we tested whether the activity-density, composition, and diversity of ground-dwelling spiders were driven by changes in vegetation structure. Field sampling was conducted using pitfall traps in bogs, heathlands, and grasslands of Brittany (Western France) in 2013. A total of 8576 spider individuals were identified up to the species level (for a total of 141 species), as well as all plant species in more than 300 phytosociological relevés. A generalised linear model showed that spider activity-density was negatively influenced by mean vegetation height and mean Ellenberg value for moisture. Indices of diversity (ɑ, β, and functional diversities) increased with increasing vegetation height and shrub cover. Variables driving spider composition were mean vegetation height, dwarf shrub cover, and low shrub cover (results from a redundancy analysis). Spiders, some of the most abundant arthropod predators, are thus strongly influenced by vegetation structure, including ground-dwelling species. Although later successional states are usually seen as detrimental to local biodiversity in Europe, our results suggest that allowing controlled development of the shrub layer could have a positive impact on the diversity of ground-dwelling spiders. [ABSTRACT FROM AUTHOR]

Body size is one of the most important individual traits, determining various other life-history traits, including fitness. Both evolutionary and ecological factors shape the body size in arthropods, but the relative contribution of abiotic drivers acting at different spatial scales has been little investigated. We aimed to identify the importance of two broad-scale variables (study region and elevation) in shaping body size of the free-running and locally abundant wolf spider Pardosa palustris (Linnaeus 1758), in contrast to the fine-scaled variable topographic position. Therefore, we set up transects along environmental gradients in the arctic-alpine ecosystems of Norway, which we analyzed using a random forest approach to identify the relative importance of topographic position, elevation, and study region on body size of P. palustris. Our approach revealed that research region was the best explanatory variable, followed by elevation and topographic position. Differences in body size were most likely a consequence of the pronounced differences in season length and the ability of P. palustris to avoid local unfavorable environmental conditions due to its high mobility. [ABSTRACT FROM AUTHOR]

Dispersal is a key process in metapopulation dynamics and metacommunity assembly as it may be affected by a variety of factors acting at different spatial scales. While dispersal is known to evolve in response to landscape-related selection pressures, local dynamics are merely driven by conditional responses, for instance by habitat quality and density. Local and regional factors are thus expected to impact dispersal, either synergistically or antagonistically. Moreover, such responses do not need to coincide among all life stages because different life stages are expected to incur different costs, either intrinsically due to for instance differences in size or extrinsically because of demographic changes. Our general objective is consequently to test for the likely opposite effects of main factors acting on dispersal, i.e. local density and habitat configuration, at different life-stages in a salt marsh inhabiting spider Pardosa purbeckensis (F.O.P.-Cambridge 1895). Using a combination of both field and laboratory experiments on pre-dispersal behaviour, we demonstrate a significant negative density-dependence for natal dispersal, but no alike effect at the adult stage. No effects of the local habitat structure were detected. Therefore, good mother body condition could be interpreted by juveniles during the phase of maternal care as suitable living conditions, decreasing emigration rate. Although dispersal is known to have a genetic basis, local factors eventually overrule this source of variation. [ABSTRACT FROM AUTHOR]

Environmental gradients can help us comprehend the range of adaptations or plasticity that a given species can exhibit in response to climatic change. In this study, we assessed the response in female body size, clutch size and egg volume to elevational gradients in closely related wolf spiders. We measured these traits in Pardosa glacialis, P. hyperborea, P. furcifera and P. palustris, collected along elevational gradients across six sites in Arctic and sub-Arctic regions (four sites in Greenland, one in Iceland and one in the Faroe Islands), although not all species were found at all sites. Body size and reproductive traits did not vary with elevation in a consistent manner among species although smaller species were more sensitive to the gradients. The positive relationship between body size and clutch size was most pronounced in the larger species, indicating that larger species are better able to translate favourable environmental conditions into a larger reproductive output. Our study illustrates that elevational gradients may not fully capture spatial variation in environmental conditions experienced by high-latitude wolf spider species. [ABSTRACT FROM AUTHOR]

While spiders constitute the most abundant and diverse arthropods in many habitats, they remained under-studied, especially in tropical rainforests. The goal of this study is to assess the spatial distribution of the spider family Ctenidae by assessing associations of species diversity and population traits among different habitat conditions. Fieldwork was carried out during 2013 in habitats varying in flooding frequency (plateau vs. flooded forest) and elevation (inselberg vs. lowland) in the Nouragues National Natural Reserve, French Guiana. Assemblage composition, population structure, and trait measurements of one dominant species were assessed using hand collection in replicated quadrats. We found strong effects on ctenid assemblages attributable to both elevation and flooding, with changes in relative abundance of species among habitats, but few correlated densities between species. At the population level, main differences in species distribution between and within habitats were detected only when juveniles were taken into account. No effect of elevation was found on the measurements of traits of the dominant species, but legs were proportionally shorter in flooded habitats, suggesting reduced active dispersal in these habitats. Our study highlights the value of complementary of measures of diversity and traits at different biological scales in Ctenidae. [ABSTRACT FROM AUTHOR]

Despite the huge diversity tropical arthropods represent, factors shaping their communities are still poorly known, especially at small spatial scales. In this study, we aimed at providing ecological and methodological insights from a short and intensive field sampling of spiders, a highly diverse group of predators. We investigated how sampling methods, habitat type and day-time affect diversity and composition of spider assemblages. The standardized sampling protocol was applied in a tropical rainforest in French Guiana, where both ground- and vegetation-dwelling (up to 2.5 meters) assemblages were sampled during day and night using supposedly complementary methods at low and high (granitic hills called inselbergs) elevations. Observed and estimated richness of vegetation-dwelling spiders, as well as their species composition, did not differ between methods (sweep netting vs. beating). Species richness was much lower in pitfall traps than in litter samples, which suggests a low mobility of grounddwelling spiders and reveals the inadequacy of the former method compared to the latter. Spider assemblage in the vegetation of inselberg was two times poorer than in lowland forests and dominated by different families, probably due to harsher habitat conditions there. Strongly different patterns were here highlighted between vegetation and ground-dwelling spider assemblages, the latter being less diversified than in the vegetation which deserves further attention. [ABSTRACT FROM AUTHOR]

Life history trade-offs are a key notion in evolutionary biology, notably for understanding how selection shapes the diversity of traits among species. Despite the frequent study of such trade-offs, few studies synchronously investigate the effects of multiple factors, such as niche specialization and adaptation to harsh environments. We compared reproduction (fecundity and egg quality) in two sympatric couples (one habitat generalist and one specialist) of congeneric wolf spider species, in both Arctic and temperate habitats. We found that specialist species at both latitudes invested more in clutch size than did generalist species. We interpret this result as an optimization of clutch production. In the Arctic, the specialist was able to invest in fecundity with increasing body size at a much higher rate than the generalist species. In the temperate habitat, both species showed similar strategies: they increased quantity and quality of offspring relative to body size at the same rate. These results are consistent with the hypothesis that Arctic species must develop distinct strategies in order not to overlap each other's ecological niches as a consequence of limited food resources or niche space. We emphasize the need to test the role of plasticity and environmentally mediated effects of competition on arthropod fitness. [ABSTRACT FROM AUTHOR]

The Bay of Aiguillon is a national French Nature Reserve of great importance for birds. Recently, the managers of the Reserve (ONCFS-LPO) paid attention to the influence of saltmarshes management on the nursery function for fish feeding in creeks at high tide. A study carried out from March to July 2012 aimed to evaluate the use of saltmarshes by fish juvenile fraction according to the mowing intensity in salt marshes surrounding creeks: ceased, irregular or annual mowing. This community approach was completed by a focus on the European sea bass Dicentrarchus labrax individual diet, vacuity index and growth, and the biomass of a main potential prey (the amphipod Orchestia gammarella). Whatever the mowing intensity, the juvenile fraction was very high for the main species, which were the grey mullet Liza ramada, the European sea bass, undetermined clupeid and the European flounder Platichthys flesus. Adult and subadult for these species were anecdotic or totally absent. Despite very different biomasses of amphipods between mown and natural sites, vacuity index, prey composition and their relative abundance in the diet of European sea bass juveniles were little different, contrary to their hypothetical growth (i.e. when assuming site fidelity), which appeared higher in non-mown site. The low distance between sampling sites could allow fish exchange over time between optimal and suboptimal creeks to feed on, as a hypothesis to explain such results. Because mowing was subsidized by European Union (EU) to favour open habitats for geese and maintain an economic activity, indirect impacts on nursery for fish called into question the appropriateness of such agro-environmental measure on natural habitats, and related fish nursery function. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including the description of physical characteristics of island tails and the ecological dynamics of marshes in Europe.

In this paper, we compare the spider faunas of two close geographical entities: Brittany (western France, 634 species) and Great Britain (UK, 639 species). There was a high percentage of shared species (67%, 513 species) and differences among families and genera were attributed to biogeography and geological history (i.e. glaciation), much less by rarity and possible under-recording. Some northern species are absent from Brittany and many southern species from Great Britain. Further surveys, mainly targeting winter maturing species, are needed. [ABSTRACT FROM AUTHOR]

Background: Knowledge about vegetation and soil seed bank composition and the processes that contribute to vegetation recovery after the removal of heavy grazing is lacking in sub-alpine ecosystems. Aims: In order to assess the effects of large herbivores on above-ground vegetation (AGV) and soil seed bank (SSB) characteristics, intensively sheep-grazed areas were compared to adjacent areas where grazing had been removed 10 years previously in a sub-alpine grassland of northern Iran. Methods: A total of 40 4-m2(2 m × 2 m) plots were established in each treatment, and soil samples were collected from each plot within a depth of 10 cm. Plant species composition was determined for each plot during the flowering stage of herbaceous species in June 2011. The seedling emergence method was used to estimate SSB composition. Results: A total of 45 species (23 annuals and 22 perennials) emerged from the soil samples of the grazed area, while the number of species emerged from the soil samples of the previously grazing area was 76 (37 annuals and 39 perennials). The removal of grazing led to a significant increase in species richness and seed density in the SSB. Species turnover of AGV was higher, and that of the SSB was similar for grazed areas compared with areas that were formerly grazed. Detrended correspondence analysis ordination of AGV composition showed a clearly separate structure between grazed plots and plots where grazing has been removed, while the segregation was less clear for SSB composition. Conclusions: We concluded that restoration of locally degraded sites cannot rely on the SSB when grazing is stopped simultaneously and unvegetated gaps are colonised by vegetative growth rather than by seed. [ABSTRACT FROM AUTHOR]

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]

A large number of studies have tried to understand the determinants of local species richness, i.e. α-diversity. Studies dealing with β-diversity are considerably less numerous but their number has increased in the recent years. In this study, we assessed the relative importance of local and landscape (i.e. composition and connectivity) variables in explaining α- and β-diversities (species turnover and nestedness) of three highly diverse groups, differing in mobility and dispersal: plants, spiders, and carabids. Sampling took place in 2013, using suction samplers for arthropods and phytosociological relevés for vegetation, in 77 hay meadows distributed along 200 km of the Loire Valley (France). We found plant α-diversity to be driven by local factors, whereas spider and carabid α-diversities were mostly determined by landscape factors (by composition and connectivity, respectively). Nestedness was negligible for the three groups. Plant β-diversity was also mainly influenced by local factors, whereas spider β-diversity was driven by landscape factors (composition and connectivity, equally). Surprisingly, carabid β-diversity was mainly influenced by local factors and landscape connectivity. Despite these differences, plant, spider, and carabid β-diversities were not different, suggesting comparable dispersal abilities and/or a low connectivity at large scale, which is in accordance with the high species turnover observed here. Managing biodiversity in meadows consequently necessitates acting at local and landscape scales, the first targeting plants and the second arthropods. [ABSTRACT FROM AUTHOR]

During range expansion, the most dispersive individuals make up the range front, and assortative mating between these dispersive phenotypes leads to increased dispersiveness (i.e. spatial sorting). The precise inheritance of dispersal, however, is to date largely unknown in many organisms, thereby hampering any progress in evaluating the adaptive potential of species during range expansion. Using the spider mite Tetranychus urticae, we therefore empirically simulated spatial sorting by means of artificial selection on a unique pre-dispersal behaviour, tightly related to emigration. To separate directionality of the response from potential drift, we mimicked a recurrent low number of founders in replicated selection regimes. Afterwards, we inferred the mode of inheritance of the pre-dispersal behaviour by performing reciprocal crosses between selected (i.e. dispersive) and non-selected (i.e. non-dispersive) mites and by screening for endosymbionts known to be associated with changes in dispersal behaviour. Despite the recurrent low number of founders, the aerial dispersal behaviour responded strongly to the imposed selection pressure. The behaviour furthermore showed a maternal inheritance, though independent of any known dispersal-related endosymbionts. Though cytoplasmic inheritance cannot fully be excluded, we attribute the observed strong and rapid, maternally influenced response in dispersal to transgenerational epigenetic effects. Consequently, we can expect fast evolutionary dynamics during range expansion in the species. [ABSTRACT FROM AUTHOR]

Discriminating closely related species can become a taxonomical challenge if a clear morphological diagnosis is lacking. Two subspecies have been recognized in Pardosa agrestis ( Westring, 1861); however, their validity is still debated. To resolve this dilemma, quantitative and qualitative traits were measured for 30 females and 30 males per site from ten localities throughout Western Europe (11 measurements on each individual) and compared between subspecies. Mean annual temperature and geographical coordinates from all sites were also included in the statistical models in order to test for variations in size over the distribution range of each subspecies. We found significant differences in body size and size of copulatory organs as well as accurate criteria of discrimination between P. a. agrestis and P. a. purbeckensis F. O. P. Cambridge, 1895, suggesting that these taxa are two valid morphological species, occurring sympatrically. We also showed that temperatures did not directly influence the size of individuals, but that one species had smaller individuals at higher latitudes (following the converse Bergmann's rule), and that both species had larger individuals in centrally sampled populations (fitting to the centre hypothesis). © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 85-96. [ABSTRACT FROM AUTHOR]

Remotely sensed data are frequently employed for monitoring vegetation and for estimating herbivore diversity. Their use for predicting predator arthropod species abundance and richness has also been investigated with success for ants and beetles in forests using normalised difference vegetation index ( NDVI) and for beetles in mountain forests using light detection and ranging data., We investigated whether vegetation indices, derived from multispectral SPOT imagery could predict abundance and species richness of ground active spiders and ground beetles in a new ecological context, the floodplain meadows of the Loire River in Western Europe. Using pitfall traps, we collected carabids and spiders in the field., Maximum vegetation height, litter-depth and plant species richness best explained species assemblages of both groups (multivariate analyses). NDVI and enhanced vegetation index ( EVI 2) were strongly related to activity-density and species richness for ground beetles only, EVI 2 being the best surrogate. Relationships between vegetation indices and spider assemblage patterns were either non-significant or weak., We demonstrated that EVI 2 is a good surrogate of the abundance and richness of carabid species in a temperate floodplain, and has potential as a low cost method for mapping arthropod assemblages at large spatial scales., Our approach provides a tool which contributes to biodiversity assessment at large spatial scales. It can also contribute to the prioritisation of conservation areas and early change detection, as carabids are keystone indicators. [ABSTRACT FROM AUTHOR]

During the last decades, urban consolidation has been developed to minimize spatial expansion of cities, yet very few studies investigated whether it would actually reduce some negative effects of urbanization on biodiversity. In this study, we compared the invertebrate assemblages associated with two distinct urban forms (compact vs. conventional), focusing on two arthropod taxa often used as bioindicators, and dominant in urban habitats: spiders and carabid beetles. The following parameters were estimated: assemblage composition, species richness, activity-density total, per species (excluding seldom-recorded species) and per size class. The field collection was performed in 2009 using pitfall traps randomly set in hedgerows within 6 sites (representing 251 traps). A total of 4,413 spiders belonging to 117 species and 2,077 adult carabid beetles belonging to 39 species were collected. We found few significant differences in carabid beetle and spider assemblages between the two urban forms. The species richness of both groups was independent from the neighborhood design. Only four species of carabid beetles and ten of spiders significantly reacted to the neighborhood design, and no difference was found among the two designs for all other species. Large carabid beetles were more abundant and small spiders less abundant in the new neighborhood design compared to the conventional one. For both carabid beetles and spiders, no difference in assemblage composition was found between neighborhood designs. We therefore conclude that urban consolidation, by permitting a higher human density with similar arthropod assemblages, could contribute to reduce biodiversity loss in cities. [ABSTRACT FROM AUTHOR]

Urbanization creates human disturbance that plays an important role in ecosystem dynamics. Most of the time, there is a time lag between disturbance and colonization. Opportunistic species with high dispersal power colonize first, while habitat specialist species with a lower power of dispersal colonize later; the communities change with time after disturbance. We hypothesize that, following the establishment of a new neighbourhood, arthropod communities will change from habitat generalists to specialists, and will be more similar to those of the adjacent countryside. We selected two groups of invertebrates often used as bioindicators, spiders and carabid beetles. The following parameters were estimated: assemblage composition, species richness, activity-density total and per life history trait (broad habitat preference). The field data were collected in 2010 within 3 towns located in France. Neighbourhoods of 10 and 30 years old were pair-matched in these towns and sampled using pitfall traps set randomly in hedgerows (120 traps in total). 2101 adult spiders belonging to 89 species were collected, whereas the 643 captured carabid beetles belonged to 24 species. We found no evidence of any significant change in carabid beetle and spider communities according to neighbourhood age. The assemblages were mainly composed of habitat generalist species. These results suggest that urban areas can be seen to be in continual state of disruption, and colonization of these areas is assumed to be relatively rapid (i.e., less than 10 years in our case study), although incomplete. [ABSTRACT FROM AUTHOR]

Dispersal and habitat selection are the main factors that affect the distribution of species in spatially structured habitat. Species typically occurring in an aggregated way are supposed to experience dispersal limitation or to be highly selective for specific habitat attributes in their environment. In order to understand the distribution pattern of a mygalomorph spider species, Atypus affinis, we conducted an intensive survey to detect correlations of spider densities with specific habitat variables and empirically tested the dispersal propensity of spiderlings. In the field, the spiders exhibited an aggregated distribution correlated with patches of heathlands (dominated by Calluna vulgaris). Contrary to our expectations, laboratory experiments revealed a very high dispersal propensity in juveniles (more than 80% of individuals dispersed at least once during two experiments). This dispersal was strongly context dependent with a pronounced negative effect of starvation and a positive effect of clutch size. Kin competition is hypothezised to be the driving force behind these high dispersal abilities. The aggregation of A. affinis is a likely result of habitat use rather than dispersal limitation. [ABSTRACT FROM AUTHOR]

Salinity interacts with many physiological functions and therefore probably influences the distribution of terrestrial fauna in tidal flooded salt marshes. The present study tests the hypothesis that the physiological tolerance of stenotopic wolf spiders for saline conditions at least partially determines their occurrence throughout salt-marsh and nonsaline habitats. The duration of survival of three stenotopic wolf spider species (Araneae: Lycosidae) with different habitat preferences is compared in a controlled laboratory experiment. The forest-dwelling Pardosa saltans, the salt-marsh resident Pardosa purbeckensis and its sister species the inland-living Pardosa agrestis are exposed to experimental conditions with different levels of salinity. Individuals (45 males and 20-45 females per treatment) are placed in individual air-tight boxes filled with water-saturated sand. Three levels of salinity are tested: nonsaline (0‰), medium saline (33-35‰) and highly saline (66-70‰). Contents of carbon, hydrogen and nitrogen and the molar ration carbon/nitrogen remain constant over time and do not differ among salinity treatments, indicating that starvation effects on survival, if any, are similar for all treatments. Conversely, body water significantly decreases over time and differs among salinity treatments, in accordance with patterns of survival. Conforming to their habitat preference, the survival of P. saltans and P. agrestis decreases quickly under highly saline conditions. Pardosa purbeckensis, however, has a high survival under both saline and nonsaline conditions. The duration of survival of females is significantly lower than that of males of P. saltans and P. purbeckensis. Durations of survival of ground-living wolf spiders exposed to salinity partly match their habitat distribution but do not explain the restriction of salt-marsh species to saline habitats. [ABSTRACT FROM AUTHOR]

As a result of an invasion by the native grass Elymus athericus (Link) Kerguélen (Poaceae) in the last 10 years, a major change in vegetation cover has occurred in salt marshes of the Mont Saint-Michel bay, Western France. The impact of such an invasion on carabid assemblages, a dominant group of terrestrial arthropods in these habitats and containing several stenotopic species, is investigated here. In our study site, carabid data are available from 1983 and 1984, allowing a comparison of species distribution ranges in salt marshes before (1983-1984) and after (2002) the E. athericus invasion. A total of 16,867 adults belonging to 40 species were caught. By considering the presence-absence of species shared between studies, we show that the invasion by E. athericus promoted the progression of non-coastal species (mainly Pterostichus s.l. spp.). This did however not interfere with resident species distributions, finally resulting in higher carabid species richness in the entire area. The species composition and abundances of carabid assemblages were also compared between natural and invaded stations in 2002. The main result is that abundances of some halophilic species decreased in one invaded plot (in case of Pogonus chalceus (Marsham 1802)) whereas the opposite pattern was observed for other species (e.g., Bembidion minimum (Fabricius 1792)). Invaded habitats were characterized by lower percentages of halophilic species and higher total species richness. [ABSTRACT FROM AUTHOR]

Salt-marsh invasions by the grass Elymus athericus (Poaceae) recently transformed usual areas dominated by Atriplex portulacoides (Chenopodiaceae) into homogeneous meadows. Two wolf spider species, Pardosa purbeckensis and Arctosa fulvolineata, show contrasting densities and habitat preferences in salt marshes (respectively dominant and co-dominant ground-living spiders) and oppositely respond to the grass invasion. This allowed us to test whether invasive species that alter habitat structure affect reproduction in addition to previously recorded changes in density. Reproductive traits (female mass, cocoon mass, number and volume of eggs, hatched cocoon as a proxy of reproduction date) were studied in both invaded and natural salt marshes during 2007 and 2008 in the Mont St-Michel Bay (France). In both species, reproductive outputs (cocoon mass) were higher in optimal habitats and volume of eggs was found to be independent from female mass, whereas the latter significantly influenced the number of eggs. In A. fulvolineata, lower reproductive outputs due to less numerous although larger eggs were found in suboptimal habitats whereas the opposite pattern was found in optimal habitats, showing the existence of plastic phenotypic trade-offs in habitats of different qualities. In P. purbeckensis, despite differences in population size among habitats, no reproductive trade-off was found. This study thus shows that two sympatric species belonging to the same family can differ in reproductive strategies and phenotypic plasticity under changes in habitat suitability. [ABSTRACT FROM AUTHOR]

The effect of inundation frequency on plant community composition, species turnover, total and growth form cover, species richness, and abundance of individual species was investigated in a newly created salt marsh (Belgium) with a gradient of inundation frequencies from 0.01% to 100%. Cover of all plant species was estimated in 119 permanent 2 × 2 m plots along seven randomly chosen transects perpendicular to the main inundation gradient in 2003, 2005, and 2007. Plant composition change clearly varied along the inundation frequency gradient. The cover of annual species increased at a higher rate at higher inundation frequencies, while cover of perennials increased at higher rate at lower inundation frequencies. Species richness and the abundance of most species increased over time, indicating general absence of competitive exclusion among species. Conversely, the abundance and frequency of Atriplex spp., Chenopodium spp., and Salsola kali strongly decreased over time, indicating their early successional character. Frequent inundations hampered plant species turnover because of the low number of species which can tolerate that environmental condition. The appearance of communities dominated by Elymus athericus or Salicornia procumbens strongly increased over time, leading to a stronger separation of plant communities and an appearance of typical salt-marsh zonation. [ABSTRACT FROM AUTHOR]

Vegetation and underground structures are known to influence flood avoidance and flood resistance in invertebrates. In bimonthly-flooded European salt marshes, recent invasions by the nitrophilous grass Elymus athericus strongly modified usual habitat structure, notably by the production of a deep litter layer. Consequently, invaded habitats provide more interstitial spaces that may act as a refuge during flood events. By using both controlled and field designs, we tested whether invaded habitats may change the ability to resist flooding by the creation of new refuges during tides for a ground-living, predatory arthropod. The wolf spider Arctosa fulvolineata was employed as a model species since it occurs abundantly in both invaded and uninvaded salt-marsh habitats. In the field, its abundance strongly decreased (divided by three) after tidal flooding in uninvaded habitats by but did not change in invaded patches. Under controlled laboratory conditions, ten times more individuals withstood simulated flooding in the presence of litter and less decided to float. The presence of litter did not influence flood resistance, i.e. survival underwater. Our results show that habitat structure (i.e. the presence of litter) influences flood-avoiding behavior of A. fulvolineata, by providing more refuges. As the invasion of E. athericus alters salt-marsh habitat structure, it may enhance population size of a rare predatory spider by changing its behavior during flooding and resulting in less deleterious impacts of tides. Yet biological invasions are detrimental for biodiversity conservation, our study shows that an invasive species might indirectly benefit a few mobile rare species in a flood-disturbed habitat. [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.

We evaluated the process of salt-marsh colonization in early successional stages of salt-marsh restoration and investigated how the sequence of species establishment related to different success factors. Vegetation data were collected by permanent plots from the restoration site and adjacent, reference salt marshes during three consecutive periods. Seed length, width and mass were used as dispersal traits, and Ellenberg moisture, salinity and nutrient indices as indicators of site suitability. Seed production in the reference site and seed bank in the restoration site were also investigated. The establishment of salt-marsh species within the restoration site was rapid (less than 5 years). The cover of plant species was not correlated between the restored and the reference sites at the first year of restoration, but this correlation was significant during the following years. Seed availability was more important in explaining the sequence of species establishment than salt and nutrient-limitation tolerance. The first colonizers are known as massive seed producers, with shorter seed length and lower seed mass, which probably increased buoyancy. Among dispersal and site traits, seed length and mass, and in a less extent salinity and nutrients, indicated a relationship with new colonizers. Despite few species have not (yet) appeared in vegetation and seed bank in the restoration site, the existence of an existing salt marsh adjacent to the restoration site is shown to be vital for fast colonization of newly created intertidal areas. [ABSTRACT FROM AUTHOR]