Summary 1. The spatial patterns of groundwater biodiversity in Europe remain poorly known, yet their knowledge is essential to understand local variation in groundwater assemblages and to develop sound conservation policies. We explore here the broad‐scale distribution of groundwater biodiversity across Europe, focussing on obligate subterranean species. 2. We compiled published distributional data of obligate subterranean aquatic taxa for six European countries (Belgium, France, Italy, Portugal, Slovenia and Spain), and conducted a detailed biological survey of six regions (one in Belgium, two in France, one in Italy, one in Slovenia and one in Spain). Based on this data set, we mapped spatial patterns of biodiversity in Europe on a cell grid with 0.2 × 0.2 ° resolution. 3. As of mid‐2006, the total number of described stygobiotic species in the six countries was 930 and the total number of genera with at least one described stygobiotic species was 191. The total number of sampling sites where at least one stygobiont had been collected was 4709, distributed in 1228 of the 4668 grid cells covering the study area. 4. Groundwater stygobiotic biodiversity was dominated by Crustacea with 757 species in 122 genera. Insects were represented by only two species of a single genus of dytiscid beetles restricted to south‐eastern France. 5. The geographic distribution of stygobionts was extremely heterogeneous. Stygobionts were recorded in 26% of the 4668 grid cells and only 33 cells had more than 20 stygobiotic species. These 33 ‘hot‐cells’ of groundwater species richness clustered in seven hotspots. 6. Endemicity was very high, with 43% of the total number of stygobiotic species restricted to a single cell, i.e. <500 km2. 7. Hotspots defined by rarity, number of genera, number of genera with only one species known in Europe, or number of monospecific genera differed markedly in ranking from those based on species richness. However, a core of four hotspots emerged in all cases: one stretching across Slovenia and northeastern Italy, one in the French Pyrenees, one in the Cévennes in southern France and one in the Rhine River valley in northeastern France. 8. Unevenness in stygobiont distribution cannot be explained solely by unevenness in sampling effort. This is indicated in particular by the fact that our comprehensive sampling survey roughly matched the level of taxonomic richness of the studied regions based on previously published information. 9. With sampling effort continuing, a twofold or higher increase in species richness can be expected in several Mediterranean areas, with a potential to discover up to 50% more new species than are currently known in the region.

Dispersal has a potentially profound effect on the dynamics of populations especially when a population occupies a patchy habitat. Ponds surrounded by terrestrial landscape are an example of patchy distribution of physical conditions and constitute “islands” for odonates. Few studies have focussed on dispersal in odonates. We have used the direct method of dispersal observing (capture‐mark‐recapture technique) in order to estimate the degree of linkage in three patchy populations of odonate localised on three ponds. We also examined the differences in dispersal ability within and among three species (Coenagrion puella, Coenagrion scitulum and Libellula depressa). The ponds were situated in southwest France on a limestone plateau. In this arid area, these ponds constitute the only surface water available and are relatively sparsely distributed. The size of the ponds ranged from 48 to 79 m2 and they were 200 and 775 m apart. We demonstrated that three factors influence the dispersal ability of these odonates. The first is represented by the abiotic factors and especially weather conditions. This determines the number of days that dispersal is possible. The second is interspecific differences. We showed that sensitivity to weather conditions, species size and species behaviour influence dispersal ability. The third factor is the intraspecific characteristics. We demonstrated that there are differences in dispersal ability according to sex and age. To conclude, we discuss the importance of pond management to maintain the existing odonate populations and to facilitate introduction of new populations in this region where little exchange occurs between ponds.

The breakdown of willow (Salix alba) and beech (Fagus silvatica) leaves and their colonization by invertebrates were studied in a third-order mountain stream (breakdown rate k = 0.0147 and 0.0052∙d−1, respectively) and a seventh-order lowland river (k = 0.0094 and 0.0027∙d−1). Willow leaves broke down three times faster than beech leaves; this difference was twice that between streams. Total invertebrate densities and biomass and the proportion of shredders were higher in the large river; therefore, differences in breakdown capacities between streams cannot be attributed to differences in invertebrate community structure. Instead, microbial processing and abiotic fragmentation are suggested as factors controlling breakdown rates. Owing to the abundance of naidids, up to 2000 invertebrates per leaf bag were recorded in the large river. These oligochaetes appeared to use litter accumulations as a microhabitat that provided shelter and a rich supply of food in the form of fine particulate organic matter. Tubificid oligochaetes accounted for 55% of total biomass on partly degraded leaves at this site. Their abundance and regular occurrence inside willow leaves suggest that tubificids enhance leaf fragmentation and possibly mediate the incorporation of organic matter in river sediments once the plant tissue is sufficiently macerated.

ABSTRACT1. The natural evolution of ponds leads to the filling up of these small ecosystems, and human intervention may sometimes be necessary to ensure their continued nature conservation interest.2. In the arid karstic region of the 'Causses du Quercy' (France), there are numerous ponds bored into parts of the calcareous rock where water cannot percolate. Without human management they are destined to disappear, although they constitute the only available surface water resource on this limestone plateau.3. Little information is available about the physical and chemical changes occurring as ponds go through different successional stages. A comparative study of three ponds at various stages of succession allowed an analysis to be made of the seasonal changes in a number of abiotic variables.4. There was evidence that the temporal and spatial variability of abiotic factors (such as temperature, water level and dissolved oxygen concentrations) increased as ponds progressed through successional stages.5. This study indicated that ponds varied in terms of plant and animal species richness and rarity, temperature, and oxygen concentration at different successional stages. Each pond supported a distinctive fauna. The results suggest that biotic diversity is, in part, driven by local-scale physical and chemical heterogeneity. Management plans should be drawn at a scale that maintains the heterogeneity of such pond networks.