The relative importance of dispersal and the local environment for species richness in two aquatic plant growth forms

Local species richness can be affected by both the dispersal process and by environmental conditions (species sorting process). The evaluation of the relative roles of these two processes contributes not only to further understanding of the mechanisms determining species richness but also to biodiversity conservation. We studied the relative importance of hydrological dispersal and water chemistry for species richness of submerged and floating‐leaved macrophytes using 31 sets of interconnected ponds with different numbers of component ponds (defined as connection class). Connection class was slightly more important than, or equally important to, water chemistry in determining species richness of floating‐leaved macrophytes. In contrast, submerged macrophyte richness was much more influenced by water chemistry than by connection class, although increasing connection class had some positive effect. Similarly, the occurrence of a particular species of submerged macrophyte was better explained by pond water chemistry than by the occurrence of the same species in the pond immediately upstream. The reverse was true for floating‐leaved macrophytes; the presence of a given species was better explained by its presence in the pond immediately upstream than by water chemistry. These results indicated that the relative importance of the two processes that shape the species richness of aquatic plants is a consequence of the growth form of the plants. However, both the dispersal process via hydrologic connection and species sorting by water chemistry play some role in determining the species richness of both floating‐leaved and submerged macrophytes.     

Environmental and spatial correlates of community composition,richness and status of boreal lake macrophytes

We assessed the relative roles of natural covariates, human disturbance (water quality and catchment land use) together with geography in driving variation in aquatic macrophyte community composition, richness and status among 101 lakes in southern and central Finland. In addition to all species together, we studied different growth forms (i.e. emergent and submerged macrophytes and aquatic bryophytes) separately. Partial redundancy analysis (taxonomic composition) and partial least-squares regression (species richness and status index) were employed to display the share of variability in macrophyte assemblages that was attributable to the environmental factors (both natural and human-affected) and the spatial filters generated through principal coordinates of neighbor matrices (PCNM).Macrophyte community composition, richness and status were explained by natural covariates, together with joint effects of human disturbance variables and space. The contributions of pure fractions of human disturbance and space were mostly modest, albeit variable among macrophyte groups and status indices. Alkalinity, historical distributions, colour, dynamic ratio and lake area were most important natural covariates for macrophytes. Of those variables influenced by human, macrophytes were mostly explained by conductivity, total phosphorus, turbidity and chlorophyll-a.Our results demonstrate, as expected, that macrophytes are dominantly affected by local environmental variables, whereas dispersal-related processes seem not to be important at regional extent. Response of macrophyte growth forms to environment and space, however, varied significantly. Community composition and richness of emergent macrophytes showed congruent response to natural covariates and human disturbance. Aquatic bryophytes, which are rarely studied along lake macrophytes, responded stronger than other growth forms to human disturbance. Contrary to our expectations, ecological indices were not affected by dispersal-related processes, but were mainly explained by natural covariates. This study is the first to investigate spatial patterns in aquatic macrophytes derived bioassessment. Geographical structuring of environmental variables and regional extent negatively affected indices, suggesting that ecological status assessment needs further development.     

Variable response of functional macrophyte groups to lake characteristics,land use,and space: implications for bioassessment

We investigated how land use at multiple scales affects functional macrophytes groups and ecological status index in the boreal region. We employed a variance partitioning analysis to quantify the relative role of lake characteristics, multiple-scaled land use (catchment, buffer zones of 100, 300 and 500 m), and space in explaining the composition and richness of functional macrophyte groups (emergent and submerged macrophytes and hydrophytes) and ecological status of macrophytes in 110 Finnish lakes. Partial redundancy analysis (community composition) and partial linear regression (richness and status index) revealed that macrophyte community composition, richness, and status index were mostly explained by the pure effect of lake characteristics, which dominated over space for most macrophyte variables. Land use adjacent to shoreline had a higher effect on emergent macrophytes and status index compared to the land use of the whole catchment. Our findings suggest that emergent macrophytes can indicate changes in water quality and hydro-morphology originated from the close vicinity of the littoral zone. Ecological quality assessment based on emergent macrophytes only is probably not sufficient, but including emergent species in the assessments is recommended, especially in the species-poor boreal region.     

Effects of an exotic invasive macrophyte (tropical signalgrass) on native plant community composition,species richness and functional diversity

1. The issue of freshwater species being threatened by invasion has become central in conservation biology because inland waters exhibit the highest species richness per unit area, but apparently have the highest extinctions rates on the planet. 2. In this article, we evaluated the effects of an exotic, invasive aquatic grass (Urochloa subquadripara– tropical signalgrass) on the diversity and assemblage composition of native macrophytes in four Neotropical water bodies (two reservoirs and two lakes). Species cover was assessed in quadrats, and plant biomass was measured in further quadrats, located in sites where tropical signalgrass dominated (D quadrats) and sites where it was not dominant or entirely absent (ND quadrats). The effects of tropical signalgrass on macrophyte species richness, Shannon diversity and number of macrophyte life forms (a surrogate of functional richness) were assessed through regressions, and composition was assessed with a DCA. The effects of tropical signalgrass biomass on the likelihood of occurrence of specific macrophyte life forms were assessed through logistic regression. 3. Tropical signalgrass had a negative effect on macrophyte richness and Shannon and functional diversity, and also influenced assemblage composition. Emergent, rooted with floating stems and rooted submersed species were negatively affected by tropical signalgrass, while the occurrence of free‐floating species was positively affected. 4. Our results suggest that competition with emergent species and reduction of underwater radiation, which reduces the number of submersed species, counteract facilitation of free‐floating species, contributing to a decrease in plant diversity. In addition, homogenisation of plant assemblages shows that tropical signalgrass reduces the beta diversity in the macrophyte community. 5. Although our results were obtained at fine spatial scales, they are cause for concern because macrophytes are an important part of freshwater diversity.     

A Century of Change in Macrophyte Abundance and Composition in Response to Agricultural Eutrophication

Clear Lake, Iowa, USA is a shallow, agriculturally eutrophic lake that has changed drastically over the past century. Eight macrophyte surveys since 1896 were pooled and examined to characterize long-term impacts of eutrophication on macrophyte community composition and relative abundance. Surveys in 1981 and 2000 revealed few submergent and floating-leaved species and a dominance in emergent species (Scirpus, Typha). Over the past century, however, species richness has declined from a high of 30 species in 1951 to 12 found today, while the community composition has shifted from submergent-(99%) to emergent-dominated floras (84%). Potamogeton praelongus was the first emergent species to disappear but was followed by several other clear water Potamogeton species. Several floating leaved and emergent genera increased in relative abundance with eutrophication, notably Nuphar, Nymphaea, Phragmites, Polygonum, Sagittaria, Scirpus, and Typha. P. pectinatus was present over the entire century due to its tolerance of eutrophic conditions. Macrophyte growth was generally light-limited, with 93% of the variance in relative abundance of submergent species explained by changes in water transparency. Clear Lake exhibits signs of alternative stable states, oscillating between clear and turbid water, coupled with high and low submerged species relative abundance. The maximum macrophyte richness occurred as the lake oscillated between submergent- and emergent-dominated states. Changes in the water level have also impacted macrophyte growth since the area of the lake occupied by emergent macrophytes was negatively correlated with water level. Strongest correlations indicated that macrophytes respond to water level variations with a 2-year time-lag.     

Macrophyte diversity and composition in relation to substratum characteristics in regulated and unregulated Danish streams

1. The objective of the present study was to examine how the physical stream environment in regulated and unregulated lowland streams affects the diversity and distribution of macrophyte communities. We analysed the abundance, distribution and composition of macrophytes, together with physical parameters, in seven regulated and seven unregulated unshaded Danish stream reaches. 2. Total macrophyte coverage was similar in the regulated and unregulated streams, but species richness and Shannon diversity were higher in the unregulated streams. Overall, we found fifty-two different species in the regulated stream reaches and sixty-two in the unregulated stream reaches. The spatial distribution of macrophytes on the stream bottom was more heterogeneous in the unregulated streams. 3. We found positive correlations between the coverage and diversity of macrophytes and the coverage of coarse-textured substratum types on the stream bottom, as well as between macrophyte coverage and diversity and substratum heterogeneity. We also found that the macrophytes were more heterogeneously distributed where substratum heterogeneity was greater. 4. The species growing both submerged and emergent were more abundant in the regulated streams, whereas species growing only submerged were more abundant in the unregulated streams. Species growing submerged, species growing both submerged and emergent, and species only growing emergent segregated differently in a canonical correspondence analysis ordination. The submerged species were primarily associated with coarser-textured substrata, whereas species growing both submerged and emergent, and species growing only emergent were associated with finer-textured substrata. 5. The most abundant species in the regulated streams, Sparganium emersum, accounting for almost one-third of the total macrophyte coverage, was primarily associated with clay and sandy bottom substrata, whereas the most abundant species in the unregulated streams, Batrachium peltatum, was primarily associated with gravel and stony substrata.     

The significance of littoral and shoreline habitat integrity to the conservation of lacustrine damselflies (Odonata)

Human development of pond and lake shorelines may significantly impact native lacustrine biota including a variety of aquatic macroinvertebrate groups. In an effort to better understand the habitat associations and sensitivities of lacustrine damselflies (Odonata: Zygoptera), we sampled adults in littoral macrophyte habitat during two flight periods at 35 randomly selected pond and lake sites in southern Maine during 2000 and 2001. Data were also collected to help characterize water body, shoreline disturbance, and aquatic vegetation at each study site. Nonmetric multidimensional scaling was used for ordination of damselfly assemblages, and coordinates from the most stable solution were related to site variables using forward stepwise multiple regression. Our results suggest that the diversity and composition of damselfly assemblages is related to the abundance and richness of littoral zone macrophytes, extent of riparian disturbance, benthic substrate granularity, and lake productivity; all variables subject to anthropogenic degradation on excessively developed waterbodies. Additionally, we developed a Habitat Tolerance Index useful for distinguishing between relative habitat specialists and generalists from among a diverse assemblage of 19 lacustrine species. Finally, species-specific damselfly associations with multiple genera of floating and emergent macrophytes were assessed using both nonparametric correlation and multiplicative regression yielding significant relationships for 17 species, including two damselflies of global conservation concern (Enallagma laterale and E. pictum). We conclude that the protection of littoral and shoreline habitat integrity, with special emphasis on emergent and floating macrophytes, is critical to the conservation of lacustrine biodiversity.     

Disturbance from pond management obscures local and regional drivers of assemblages of primary producers

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Macrophytes as indicators of stream condition in the wet tropics region,Northern Queensland,Australia

This study investigates the use of aquatic macrophytes as indicators of stream condition in catchments with varied land use and levels of riparian disturbance in the Wet Tropics region of North Queensland (Australia), a region of global significance in terms of faunal and floral diversity. In a paired catchment design spatial variations in macrophyte assemblage structure were characterised using multivariate and univariate techniques. Seven metrics were trialled: total macrophyte cover, species richness, % alien taxa, % native taxa, % submerged taxa, % emergent taxa and % Poaceae. Forty-four macrophyte taxa were recorded from the study area. Poaceae, Cyperaceae and mosses were the most frequently recorded taxa. Upper catchment areas in all tributaries surveyed were dominated by mosses and Cladopus queenslandicus (Domin) C.D.K. Cook (Podestemaceae). This assemblage occurred in areas with intact riparian canopy cover and good overall riparian condition. Macrophyte assemblages in lower catchment areas were distributed along gradients of riparian disturbance. Simultaneous autoregression model coefficients indicated that riparian condition had a negative influence on macrophyte cover, species richness and the proportions of alien taxa, emergent taxa and Poaceae present at sites in the Wet Tropics. Macrophyte metrics were not strongly influenced by the types of land use or water quality. These findings suggest that a riparian condition assessment would provide an adequate first assessment of the state of aquatic macrophyte assemblages in Wet Tropics streams.     

西太湖水生植物时空变化

水生植物在浅水湖泊生态系统中具有十分重要的作用。根据中国科学院太湖湖泊生态系统研究站1989年以来的常规监测资料,将西太湖（除东太湖以外的湖区）划分为9个区,采用点截法（point intercept method）,于2002～2005年对各区水生植物的种类、生物量和空间分布情况进行了6次调查。结果表明：西太湖现有水生植物16种,分属于11科12属;水生植物总面积约10220hm^2,其中沉水植物分布面积约占64．58％;挺水植物约占0．29％;漂浮植物约占38．16％。各个种之间生物量差异显著,马来眼子菜、荇菜、芦苇的生物量在所有水生植物中居前3位。多样性分析表明,水生植物种类4a来未发生明显变化,但种类和生物量季节性差异较大。水生植物呈环状分布在距湖岸5km以内的水域和部分岛屿周围,东岸和南岸为水生植物的主要集中分布区域,分布区连续性好,且水草种类齐全。挺水植物种类单一,仅有芦苇（Phragmites communis）一种,分布区域多限于水深小于1．6m的湖岸;沉水植物共有8种,为水生植物的主要组成部分,马来眼子菜（Potamogeton malaianus）的分布频度最高,在西山岛周围水域逐年扩张,成为该区域的先锋种;漂浮植物3种,主要以荇菜（Nymphoides peltata）为主,在七都水域有逐渐扩张的趋势。马来眼子菜、芦苇、荇菜表现出对水环境较强的适应能力,目前为西太湖的3个优势种。20世纪50年代以来,西太湖水生植物种类减少了50种,其中水质下降是导致水生植物种类不断减少甚至消失的一个重要原因。围网养殖和不合理的捕捞方式也对局部水域的植物造成极大的破坏。水生植物生存环境日益严峻,种群单一化趋势日益明显。     

Influence of nutrients, submerged macrophytes and zooplankton grazing on phytoplankton biomass and diversity along a latitudinal gradient in Europe

In order to evaluate latitudinal differences in the relationship of phytoplankton biomass and diversity with environmental conditions in shallow lakes, we sampled 98 shallow lakes from three European regions: Denmark (DK), Belgium/The Netherlands (BNL) and southern Spain (SP). Phytoplankton biomass increased with total phosphorus (TP) concentrations and decreased with submerged macrophyte cover across the three regions. Generic richness was significantly negatively related to submerged macrophyte cover and related environmental variables. Zooplankton:phytoplankton biomass ratios were positively related to submerged macrophyte cover and negatively to phytoplankton generic richness in DK and BNL, suggesting that the low generic richness in lakes with submerged macrophytes was due to a higher zooplankton grazing pressure in these regions. In SP, phytoplankton generic richness was not influenced by zooplankton grazing pressure but related to conductivity. We observed no relationship between phytoplankton generic richness and TP concentration in any of the three regions. The three regions differed significantly with respect to mean local and regional generic richness, with BNL being more diverse than the other two regions. Our observations suggest that phytoplankton diversity in European shallow lakes is influenced by submerged macrophyte cover indirectly by modulating zooplankton grazing. This influence of submerged macrophytes and zooplankton grazing on phytoplankton diversity decreases from north to south.     

Environmental drivers of aquatic macrophyte assemblages in ponds along an altitudinal gradient

The aim of this study was to explore the environmental drivers of the aquatic macrophyte assemblage in a large, heterogeneous Spanish region covering a wide altitudinal range. We hypothesized that physicochemical variables affecting assemblages would differ depending on altitude. The study was conducted in 46 plateau ponds and 21 mountain ponds. Our results revealed a shift in hydrophyte assemblage composition and structure along an altitude and water chemistry gradient. However, altitude was not a good predictor of species richness. Conductivity and nutrient concentrations were higher in plateau ponds than in mountain ponds and binary logistic regression showed that conductivity was the best variable for differentiating between both pond types. Canonical correspondence analysis indicated that conductivity was the main factor responsible for the species distribution in both pond types. Generalized linear models showed that in plateau ponds, total phosphorus and mean depth were the strongest predictors of submerged macrophyte coverage, and no model could be created for richness. In the mountain ponds, conductivity and pond area explained coverage of submerged plants, while richness was related to pond area. Our results corroborated the hypothesis to be tested, and the conclusions obtained may be of relevance for making decisions on conservation and restoration.     

The role of solid waste materials as habitats for macroinvertebrates in a lowland dam reservoir

Eight hypereutrophic phytoplankton dominated ponds from the Brussels Capital Region (Belgium) were biomanipulated (emptied with fish removal) to restore their ecological quality and reduce the risk of cyanobacterial bloom formation. Continuous monitoring of the ponds before and after the biomanipulation allowed the effects of the management intervention on different compartments of pond ecosystems (phytoplankton, zooplankton, submerged vegetation and nutrients) to be assessed. Fish removal resulted in a drastic reduction in phytoplankton biomass and a shift to the clear-water state in seven out of eight biomanipulated ponds. The reduction in phytoplankton biomass was associated with a marked increase in density and size of large cladocerans in six ponds and a restoration of submerged macrophytes in five ponds. The phytoplankton biomass in the ponds with extensive stands of submerged macrophytes was less affected by planktivorous fish recolonisation of some of the ponds later in the summer. The two non-vegetated ponds as well as one pond with sparse submerged vegetation showed a marked increase in phytoplankton biomass associated with the appearance of fish. Phytoplankton biomass increase coincided with the decrease in large Cladocera density and size. One pond lacking submerged macrophytes could maintain very low phytoplankton biomass owing to large Cladocera grazing alone. The results of this study confirmed the importance of large zooplankton grazing and revegetation with submerged macrophytes for the maintenance of the clear-water state and restoration success in hypereutrophic ponds. They also showed that large Cladocera size is more important than their number for efficient phytoplankton control and when cladocerans are large enough, they can considerably restrain phytoplankton growth, including bloom-forming cyanobacteria, even when submerged vegetation is not restored. The positive result of fish removal in seven out of eight biomanipulated ponds clearly indicated that such management intervention can be used, at least, for the short-term restoration of ecological water quality and prevention of noxious cyanobacterial bloom formation. The negative result of biomanipulation in one pond seems to be related to the pollution by sewage water. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

Influence of submerged vegetation and fish abundance on water clarity in peri-urban eutrophic ponds

Despite the presence of high nutrient concentrations, most ponds located around Brussels (Belgium) show a considerable variation in turbidity. The importance of submerged macrophytes in maintaining the clear-water state requires identification of the main factors determining macrophyte abundance and diversity in ponds and small lakes. In this study, the inter-relationships between submerged macrophyte cover, fish abundance and turbidity were investigated in 13 eutrophic peri-urban ponds. Along a turbidity gradient, vegetation switched from dominance by Stoneworts (Chara and Nitella spp.) in the clearest ponds, to dominance by Potamogeton pectinatus in ponds with a slightly lower water transparency. Despite the presence of both P. pectinatus and Stoneworts in each of the vegetated ponds, only one became dominant. Only a very low abundance (around 20%) of submerged vegetation was found in ponds of intermediate turbidity, while macrophytes were absent in turbid ponds. Multi- and univariate analysis showed a marked difference in chemical, physical and biological properties between ponds deliberately used for fish stocking and ponds that were not. Macrophyte cover was significantly negatively correlated with turbidity and plankti-benthivorous fish abundance. No such correlation was observed with piscivorous fish abundance, except for pike that were associated with a charophyte vegetation in the study ponds. The strong relationship found between fish abundance and turbidity, its negative effect on submerged vegetation cover, and the importance of submerged vegetation in controlling phytoplankton abundance, should be taken into account when selecting ponds for fish stocking. It also suggests that the study ponds have a good potential for ecological quality restoration by biomanipulation.     

Simple pond restoration measures increase dragonfly (Insecta: Odonata) diversity

Ponds are home to a diverse community of specialized plants and animals and are hence of great conservation concern. Through land-use changes, ponds have been disappearing rapidly and remaining ponds are often threatened by contamination and eutrophication, with negative consequences for pond-dependent taxa like amphibians or dragonflies (Odonata: Anisoptera and Zygoptera). Increasingly, restoration measures such as removal of shading terrestrial vegetation or submerged organic matter are implemented to counteract current threats, but how these measures affect the target taxa is rarely assessed. We tested if and how simple pond restoration measures affectionate diversity. We propose that pond restoration influences the light regime, which promotes aquatic and riparian vegetation important for different dragonfly life stages, thus increasing their diversity. Additionally, we assume that this changes dragonfly species composition between restored and unrestored ponds. We surveyed exuviae in the riparian and aquatic vegetation along the shore of 29 (12 restored, 17 unrestored) man-made ponds in southwest Germany and assessed environmental variables known to affect dragonfly diversity. We identified the cover of tall sedges and submerged macrophytes as the driving biotic variables for dragonfly diversity and species composition, with restoration measures affecting submerged macrophyte cover directly but tall sedges indirectly via available sunlight. This study demonstrates that simple restoration measures not only have a positive effect on overall dragonfly diversity, but also increase habitat suitability for several species that would otherwise be absent. We therefore propose dragonflies as a suitable flagship group for pond conservation.     

The response of amphibian communities to fish and habitat features in Mediterranean permanent ponds

Generalized linear models were used to test the effect of fish, using ponds with and without fish and habitat features as covariates, on richness and abundance of amphibian species. Five fish species and six amphibian species were recorded in 60 permanent ponds located in central Italy. The choice of covariates (macrophyte cover and pond surface area) was made after studying the correlations. The richness of amphibian species was not significantly affected by fish presence or macrophyte cover, in line with previous studies, since almost all the fish species were non-predatory. However, abundance of urodeles (newts) was negatively affected by fish and positively affected by macrophyte cover. Although fish may strongly influence the abundance and composition of amphibian communities, the results indicate that the cover of aquatic macrophytes may increase the available habitat for amphibians and therefore their abundance. Anuran species preferred ponds where fish were present, since both groups preferred larger ponds. Concordance between fish and amphibian species composition was not found by the Mantel and Partial Mantel tests. This indicates that the fish assemblages do not predict which amphibian species occur in the pond.     

Biodiversity patterns of nutrient-rich fish ponds and implications for conservation

Nutrient-rich water bodies are usually expected to host low species richness at the local scale (water body). Nevertheless, they can support a diverse and sometimes unique biodiversity when diversity is considered at a regional scale. This discrepancy between the two scales is well documented for natural water bodies, but little is known about biodiversity of artificial water bodies, like fish ponds. We hypothesise that nutrient-rich water bodies can collectively host high species richness at the regional scale. Thus, these are important ecosystems for the regional conservation of biodiversity. We investigated 84 fish ponds in the Dombes region, France, with five taxonomic groups: macrophytes, phytoplankton, macroinvertebrates, dragonflies, and amphibians. Species richness patterns were determined for α- (single pond), β- (between ponds), and γ- (regional pond network) levels. For most studied species groups, richness per fish pond and at the regional level proved to be relatively high in comparison with natural ponds in other landscapes. Contribution of α-diversity to regional diversity was highest for dragonflies with 41 %, and lowest for amphibians and macrophytes with 16 and 18 %, respectively. For macroinvertebrate families and phytoplankton genera it was intermediate. Contribution of β-diversity to regional diversity was similar for all species groups with 22–25 %. Furthermore, some ponds hosted a large number of less frequent species and some endangered species, indicating that the conservation of biodiversity of fish ponds must be established at a regional scale.     

Macrophyte loss drives decadal change in benthic invertebrates in peatland drainage ditches

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Remote sensing of phytoplankton-macrophyte coexistence in shallow hypereutrophic fluvial lakes

We investigated with remote sensing (APEX images) the coexistence of phytoplankton and macrophytes in three interconnected shallow and hypereutrophic fluvial lakes (Mantua Lakes, Northern Italy). High concentrations of chlorophyll-a, up to 60 mg m^?3, were determined in the open water between well-developed stands of floating-leaved, submerged, and emergent macrophytes. Our data suggest a general inhibition of phytoplankton by macrophytes, evidenced by decreasing chlorophyll-a concentrations in proximity of macrophyte stands. Chlorophyll-a concentrations halved in the proximity of emergent stands (~6 mg m^?3 within 21 m from the stand border) when compared to the outer zones (~13 mg m^?3). Contrasting trends were observed for submerged stands, where concentrations decreased inwards from ~8 to ~3 mg m^?3. Floating leaved stands had a neutral effect, chlorophyll-a being nearly constant in both inner and outer zones. Overall, remotely-sensed data allow evaluation of quantitative and spatially defined interactions of macrophytes and phytoplankton at the whole ecosystem scale.     

The distribution of pond snail communities across a landscape: separating out the influence of spatial position from local habitat quality for ponds in south-east Northumberland,UK

Ponds support a rich biodiversity because the heterogeneity of individual ponds creates, at the landscape scale, a diversity of habitats for wildlife. The distribution of pond animals and plants will be influenced by both the local conditions within a pond and the spatial distribution of ponds across the landscape. Separating out the local from the spatial is difficult because the two are often linked. Pond snails are likely to be affected by both local conditions, e.g. water hardness, and spatial patterns, e.g. distance between ponds, but studies of snail communities struggle distinguishing between the two. In this study, communities of snails were recorded from 52 ponds in a biogeographically coherent landscape in north-east England. The distribution of snail communities was compared to local environments characterised by the macrophyte communities within each pond and to the spatial pattern of ponds throughout the landscape. Mantel tests were used to partial out the local versus the landscape respective influences. Snail communities became more similar in ponds that were closer together and in ponds with similar macrophyte communities as both the local and the landscape scale were important for this group of animals. Data were collected from several types of ponds, including those created on nature reserves specifically for wildlife, old field ponds (at least 150 years old) primarily created for watering livestock and subsidence ponds outside protected areas or amongst coastal dunes. No one pond type supported all the species. Larger, deeper ponds on nature reserves had the highest numbers of species within individual ponds but shallow, temporary sites on farm land supported a distinct temporary water fauna. The conservation of pond snails in this region requires a diversity of pond types rather than one idealised type and ponds scattered throughout the area at a variety of sites, not just concentrated on nature reserves. Handling editor: B. Oertli