Local, among-site, and regional diversity patterns of benthic macroinvertebrates in high altitude waterbodies: do ponds differ from lakes?

In this study we aimed at comparing invertebrate diversity of high altitude lakes and ponds along hierarchical spatial scales. We compared local, among-site, and regional diversity of benthic macroinvertebrates in 25 ponds and 34 lakes in the Tatra Mountains, central Europe. The ponds showed significantly lower local diversity, higher among-site diversity and similar regional diversity than the lakes. The species–area relationships (SAR), habitat heterogeneity, and environmental harshness are assumed as drivers for the local diversity patterns. An ecological threshold separating pond and lake systems emerged at an area of 2 ha, where the SAR pattern changed significantly. Differences in species turnover between these systems were likely driven by greater environmental variability and isolation of the ponds. High altitude ponds neither significantly support greater regional diversity nor higher number of unique taxa than lakes. The higher among-site diversity of ponds relative to lakes highlights the relevance of ponds for regional diversity in mountain areas.     

The evolutionary species pool hypothesis and patterns of freshwater diatom diversity along a pH gradient

Aim To interpret the unimodal relationship between diatom species richness and lake pH within the context of the evolutionary species pool hypothesis (SPH). We test the following primary prediction arising from the SPH: the size of the potential species pool (PSP) will increase along a gradient representing the historical commonness of different pH environments (pH commonness). To do this we assume that the present‐day spatial dominance of near‐neutral pH conditions compared with acidic and alkaline conditions reliably mimics the relative spatial availabilities of historical pH conditions among freshwater lakes. We also determine whether local richness represents a constant proportion of PSP size along the pH commonness gradient. Location Two hundred and thirty‐four lakes distributed over a 405,000 km² region of the north‐eastern United States of America. Methods Sediment diatom morphospecies lists and pH data were acquired from the US Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) website. Using 248 morphospecies that occurred in at least 10 of the 234 lakes, four different measures of PSPs were calculated along the pH gradient. Local species richness was equated with the number of species occurring within the lake. Alpha diversity was equated with the average species richness of lakes with similar pH values. A combination of statistical methods were employed, including correlations, quadratic regression and piecewise regression. Results PSP size increased significantly with pH commonness for all four measures of PSP size, thus supporting the primary prediction of the evolutionary SPH. Local richness comprised a larger proportion of the PSP within acidic lakes than within circumneutral lakes. Alpha diversity and lake species richness both increased significantly with pH commonness, but the former did so in a two‐step fashion. We test and reject several alternative contemporary time‐scale explanations for our findings. Main Conclusions Our findings are consistent with the hypothesis that diatom taxonomic richness is presently lower within acidic and highly alkaline lakes than in circumneutral lakes owing to the limited opportunity in space and/or time for the evolution of suitably adapted species. Whereas ecological processes can explain why certain species are excluded from particular habitats, e.g. acidic lakes, they cannot account for why so few species are adapted to those habitats in the first place.     

Incorporating landscape connectivity into household pond configuration in a hilly agricultural landscape

Manmade ponds are common landscape features in rural areas and also important habitats for maintaining biodiversity. However, they are vulnerable to anthropogenic activities, land-use changes, and habitat degradation; many ponds being filled or (re)created arbitrarily. Little attention has been paid to quantifying the spatial structure of these manmade ponds at a landscape scale, nor to their potential functional benefits in promoting ecological flows and interactions between habitats for whole-ecosystem integrity. In this study, we investigated the patch-based landscape connectivity of household ponds, a particular type of domestic pond prevalent in hilly rural areas of China, by using least-cost path modelling and graph theory based network analysis. A hierarchical network was modelled consisting of 4606 individual ponds, 373 pond patches and 772 potential links within a 1.5-km threshold distance. Network importance analysis revealed that the largest pond patch contributes 24.5 % to network building and that patches with larger areas are generally more important. In contrast, the importance of the simulated links is only 2.3 % at most, indicating that the network has spatial redundancy which can strengthen resilience to uncertain disturbances. Our study moves beyond network simulation and importance assessment by directly relating the connectivity analysis to a real construction context through the incorporation of a spatially explicit land suitability analysis. This approach systematises the analysis of pond landscapes and guides integration with the wider landscape matrix. It provides operational spatial suggestions for holistic landscape planning across local to regional scales.     

Evidence for morphological and adaptive genetic divergence between lake and stream habitats in European minnows (Phoxinus phoxinus, Cyprinidae)

Natural selection drives local adaptation, potentially even at small temporal and spatial scales. As a result, adaptive genetic and phenotypic divergence can occur among populations living in different habitats. We investigated patterns of differentiation between contrasting lake and stream habitats in the cyprinid fish European minnow (Phoxinus phoxinus) at both the morphological and genomic levels using geometric morphometrics and AFLP markers, respectively. We also used a spatial correlative approach to identify AFLP loci associated with environmental variables representing potential selective forces responsible for adaptation to divergent habitats. Our results identified different morphologies between lakes and streams, with lake fish presenting a deeper body and caudal peduncle compared to stream fish. Body shape variation conformed to a priori predictions concerning biomechanics and swimming performance in lakes vs. streams. Moreover, morphological differentiation was found to be associated with several environmental variables, which could impose selection on body and caudal peduncle shape. We found adaptive genetic divergence between these contrasting habitats in the form of 'outlier' loci (2.9%) whose genetic divergence exceeded neutral expectations. We also detected additional loci (6.6%) not associated with habitat type (lake vs. stream), but contributing to genetic divergence between populations. Specific environmental variables related to trophic dynamics, landscape topography and geography were associated with several neutral and outlier loci. These results provide new insights into the morphological divergence and genetic basis of adaptation to differentiated habitats.     

The spatial and temporal heterogeneity of macrophyte communities in thirty small,temporary ponds over a period of ten years

Ponds are important habitats within many landscapes because of the diversity of wildlife they support. This arises in part because of the heterogeneity of ecological communities found in neighbouring ponds but this variation has proved difficult to explain. Chance and unrecorded historic events have often been emphasised as explanations. This study describes the development of spatial heterogeneity and the role of historic events in the development of pond plant macrophyte communities from the ponds’ creation until ten later using thirty small, adjacent temporary ponds in Northumberland. Plant communities showed significant spatial variation from the first year onwards. Metacommunity spatial patterns changed over time but even after ten years several distinct macrophyte communities persisted in different ponds. The outcome was that a greater variety of pond communities persisted than was likely if a single, larger pond had been created on the site. The spatial patterns of the plants communities were compared to spatial variation of summer dry‐phase and winter inundation. Macrophyte heterogeneity appeared to result from deterministic change which would have been difficult to detect in a snap‐shot survey not knowing the history of the ponds. Winter inundation showed significant spatial trends every year which mirrored the changing distribution of macrophyte communities between ponds. The proximate influence of the inundation is ultimately determined by the position of each pond in the landscape so that the marked spatial and temporal heterogeneity of plant communities was strongly influenced by small scale variation in hydrology. The results suggest that the heterogeneity of pondlife across a landscape may be deterministic when recorded over a longer time period and not due to chance, but that the determining environmental factors are highly contingent on the locality of the pond.     

Determinant landscape‐scale factors on pond odonate assemblages

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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     

Effects of pH and calcium on soil organic matter dynamics in Alaskan tundra

In Northern Alaska (AK), large variation in biogeochemical cycling exists among landscapes underlain by different aged geologic substrates deposited throughout the Pleistocene. Younger, less weathered landscapes have higher pH (6.5 vs. 4.5), ten-fold higher exchangeable cation concentrations, and slower rates of microbial activity than older, more weathered landscapes. To tease apart the effects of polyvalent cations vs. pH on microbial activity and organic matter solubility and stabilization, we conducted a soil incubation experiment. We collected soils near Toolik Lake, Alaska from replicated sites along a chronosequence of landscape ages ranging from 11,000 to 4.8 million years since glaciation and manipulated soil pH and calcium (Ca, the dominant polyvalent cation across all landscape ages) using a factorial experimental design. As expected, microbial respiration was inhibited by high Ca concentrations at both pH 6.5 and 4.5. In contrast, soils with circumneutral pH (but similar Ca concentrations) exhibited higher rates of microbial respiration than soils with acidic pH, opposite of in situ patterns. Manipulated soils with acidic (4.5) pH (but similar Ca concentrations) exhibited higher cumulative dissolved organic nitrogen (DON) in leachates than soils with circumneutral (6.5) pH, similar to in situ patterns of leaching among landscape ages, but there was no consistent effect of pH on dissolved organic carbon (DOC) in leachates across landscape ages. Increasing Ca concentration inhibited cumulative DOC in leachates at circumneutral pH as expected, but had no effect on DOC or DON in leachates at acidic pH. Our results indicate that both polyvalent cation concentration and pH likely influence microbial activity in tundra soils, suggesting that heterogeneity in geochemical factors associated with landscape age should be considered in models of tundra biogeochemistry.     

Patterns in the organization of Cerrado pond biodiversity in Brazilian pasture landscapes

There is a worldwide concern on the loss of pond biodiversity in human dominated landscapes. Nevertheless, agricultural activities appear to increase pond number in the Brazilian Cerrado through damming streams for cattle raising. These man-made ponds may represent important landscape features, but their importance to regional biodiversity has not yet been studied. Here, we evaluated differences in alpha and beta diversity under a multi-taxonomic approach, as well as tested pond size as the main driver of local species richness. We also assessed the importance of environmental heterogeneity through the analysis of the regional species accumulation curves (SAC). The overall result suggests that species turnover was the major component of regional biodiversity for all groups. Major physical and chemical water conditions had no effects on algae, macrophytes, water bugs, and birds species richness. Pond size had a significant effect on Odonata and fish species richness, while water beetles and amphibians were influenced by trophic conditions. Results from regional SAC show variations among different taxonomic groups regarding landscape heterogeneity: only algae, fish, and birds do not reached to an asymptote and had higher z-values. Our results highlight the importance of ponds for biodiversity conservation in increasingly agricultural landscapes in central Brazil.     

The interplay between local and landscape scales on the density of pond-dwelling anurans in subtropical grasslands

We investigated the role of local and landscape environmental variables on anurans density classified as habitat specialists and generalists in grassland landscapes, known as South Brazilian grasslands (SBG). In this region, we surveyed 187 ponds distributed over 40 landscape sampling units. For each pond, 31 local environmental variables were measured. Each landscape sampling unit was embedded within a larger regional sampling unit with different landscape properties. For each landscape and regional sampling units, 16 landscape metrics were extracted from a land cover and use map. We recorded 35 species, eleven of which are specialists in the SBG. The specialists were affected by 11 local and 2 landscape environmental variables, while generalists were affected by 14 local and one landscape environmental variable. Thus, specialists and generalists presented different relationships with local and landscape variables, but in general local variables had a greater influence on the density of anurans than the landscape variables. However, the landscape indirectly influenced local variables because higher quality ponds were in landscapes with higher percentages of natural habitat. In conclusion, reproductive sites with higher local quality and located within landscapes with higher percentages of natural grasslands are essential to conserve anurans in this habitat. Effective conservation of such sites would benefit from further studies that assess effects of land use and biotic integrity of ponds, which can help to determine (a) the relative effects of local habitat quality of ponds and (b) the effectiveness of protecting ponds and their local surroundings for anuran conservation in SBG. Abstract in Portuguese is available with online material.     

Variable history of land use reduces the relationship to specific habitat requirements of a threatened aquatic insect

The hutchinsonian realized niche of a species is the most common tool for selecting the actions needed when restoring habitats and establishing conservation areas of species. However, defining the realized niche of a species is problematic due to variation across spatial and temporal scales. In this study we tested the hypothesis that habitat parameters defining the realized niche of a species can be derived from a regional study and that national changes in land use influence the perception of the realized niche across different landscapes. We described the realized habitat niche of the threatened dragonfly Leucorrhinia pectoralis, in four Estonian landscapes which all have undergone more than 20 years of habitat degradations. We recorded the presence/absence of L. pectoralis and measured 7 habitat variables for 140 lakes and ponds located in one restored and three un-restored landscapes. Lake size and proportion of short riparian vegetation were significantly positive parameters determining the presence of L. pectoralis across landscape types. The species was much more habitat specific in the restored landscape, with larger influence of other habitat parameters. Our data suggest that the realized niche of the species in the un-restored landscapes was constrained by the present-day habitats. The study demonstrate that if a species realized niche is derived from local distribution patterns without incorporating landscape history it can lead to an erroneous niche definition. We show that landscape restoration can provide knowledge on a species’ habitat dependencies before habitat degradation has occurred, provided that restoration mitigation reflects the former landscape characteristics.     

Phylogenetics of pond and lake lifestyles in Chaoborus midge larvae

Abstract . Aquatic invertebrates experience strong trade-offs between habitats due to the selective effects of different predators. Diel vertical migration and small body size are thought to be effective strategies against fish predation in lakes. In the absence of fish in small ponds, migration is ineffective against invertebrate predators and large body size is an advantage. Although widely discussed, this phenomenon has never been tested in a phylogenetic context. We reconstructed a mitochondrial DNA (mtDNA) tree to investigate the phylogenetic distribution of pond and lake lifestyles among 10 species of northern temperate Chaoborus midge larvae. The mtDNA tree is similar to previous morphological trees for Chaoborus , the only difference being the disruption of the subgenus Chaoborus sensu stricto. At least three shifts have occurred between pond and lake lifestyles, each time associated with evolution of diel vertical migration in the lake taxon. The trend in larval body size with habitat type is sensitive to tree and character reconstruction methods, only weakly consistent with the effects of fish predation. Despite long time periods over which adaptation to each habitat type could have occurred, there remains significant phylogenetic heritability in larval body size. The tree provides a framework for comparative studies of the metapopulation genetic consequences of pond and lake lifestyles.     

Hydroperiod,predators and the distribution of physid snails across the freshwater habitat gradient

1. Studies of species distributions across environmental gradients further our understanding of mechanisms regulating species diversity at the landscape scale. For some freshwater taxa the habitat gradient from small, shallow and temporary ponds to large, deep and permanent lakes has been shown to be an important environmental axis. Freshwater snails are key players in freshwater ecosystems, but there are no comprehensive studies of their distributions across the entire freshwater habitat gradient. Here we test the hypothesis that snail species in the family Physidae are distributed in a non‐random manner across the habitat gradient. We sampled the snails, their predators and the abiotic environment of 61 ponds and lakes, spanning a wide range in depth and hydroperiod. 2. Temporary habitats had the lowest biomass of predators. Shallow permanent ponds had the highest biomass of invertebrate predators but an intermediate fish biomass. Deep ponds and lakes had the highest fish biomass and intermediate invertebrate biomass. Five species of physids occurred in the regional species pool and 60 of the 61 ponds and lakes surveyed contained physid snails. Each pond and lake contained an average of just 1.2 physid species, illustrating limited membership in local communities and substantial among‐site heterogeneity in species composition. 3. Physids showed strong sorting along the habitat gradient, with Physa vernalis found in the shortest hydroperiod ponds and Aplexa elongata, P. gyrina, P. acuta and P. ancillaria found in habitats of successively greater permanence. When organised into a site‐by‐species incidence matrix with sites ordered according to their hydroperiods, we found the pattern of incidence to be highly coherent, showing that much of the heterogeneity in species composition from one pond to another is explained by hydroperiod. We also found that the number of species replacements along this gradient was higher than random, showing that replacement is more important than nesting in describing species composition in ponds of different hydroperiod. 4. Discriminant analysis showed that pond depth, invertebrate biomass and fish biomass were the best predictors of species composition. Analysis of these niche dimensions showed that P. vernalis and A. elongata were most successful in shallow, temporary ponds with few predators. P. gyrina and P. acuta were typically found in ponds of intermediate depth and high predator abundance. P. ancillaria was found in the deepest lakes, which had abundant fish predators but few invertebrate predators. Of the five species considered, P. ancillaria, P. vernalis and A. elongata were relatively specialised with regard to key habitat characteristics, P. gyrina was moderately generalised and P. acuta was remarkably generalised, since it alone occurred across the entire freshwater habitat gradient. The exceptional habitat breadth of P. acuta stands in contrast to distributional studies of other freshwater taxa and deserves further attention.     

Correlation of surface sediment diatoms with the present lake water pH in 28 Algoma lakes,Ontario, Canada

The surface sediment diatom analysis of 28 Algoma lakes (pH 4.40–8.13) indicates that even though each lake has a widely different aquatic environment and characteristic diatom assemblage, a definite relationship exists between the lake water pH and their diatom assemblages. In the acidic lakes acidobiontic and acidophilous diatom species predominate whereas in circumneutral and alkaline lakes circumneutral and alkaliphilous diatoms were most common. Cluster analysis of the pH indicator diatom assemblages grouped the study lakes into three distinct cluster groups. These groups also closely corresponded to lake water pH. On the basis of published ecological information as well as their presence in our study lakes, the pH indicator status of a number of diatom taxa have been discussed. A detailed listing of the diatom taxa identified and their pH indicator status is provided in order to facilitate their use in future diatom-inferred pH studies.     

Role of substrate and landscape context in early succession: An experimental approach

Both local site conditions and landscape context influence the course of succession, but there is a lack of experimental studies on the relative importance of these two factors. It is hypothesised that convergence vs. divergence in succession is determined by the interplay of site factors, such as type of substrate and the nature of the surrounding landscape. In order to evaluate the role of substrate and surrounding landscape in the initial development of vegetation, experimental plots with tertiary clay, sand, peat, sterilised local soil and undisturbed local soil as a control were established in two contrasting regions, and the cover of all the species present was recorded annually for 10 years. In early succession, vegetation was affected by both the substrate and surrounding landscape, but their effects resulted in different trends. The importance of the substrate gradually decreased, while that of the landscape context increased. In the course of succession the vegetation between the two regions diverged and converged within each region. We concluded with regard to the divergence vs. convergence dichotomy in succession: if contrasting habitats occur in the same or similar landscapes, convergence is expected, whereas if similar or the same habitats are located in contrasting landscapes, divergence is expected. For the remaining combinations, i.e. contrasting habitats in contrasting landscapes or the same habitats in the same or a similar landscape, successions may exhibit no or only slight divergence or convergence.     

Urban ponds as an aquatic biodiversity resource in modified landscapes

Urbanization is a global process contributing to the loss and fragmentation of natural habitats. Many studies have focused on the biological response of terrestrial taxa and habitats to urbanization. However, little is known regarding the consequences of urbanization on freshwater habitats, especially small lentic systems. In this study, we examined aquatic macro‐invertebrate diversity (family and species level) and variation in community composition between 240 urban and 782 nonurban ponds distributed across the United Kingdom. Contrary to predictions, urban ponds supported similar numbers of invertebrate species and families compared to nonurban ponds. Similar gamma diversity was found between the two groups at both family and species taxonomic levels. The biological communities of urban ponds were markedly different to those of nonurban ponds, and the variability in urban pond community composition was greater than that in nonurban ponds, contrary to previous work showing homogenization of communities in urban areas. Positive spatial autocorrelation was recorded for urban and nonurban ponds at 0–50 km (distance between pond study sites) and negative spatial autocorrelation was observed at 100–150 km and was stronger in urban ponds in both cases. Ponds do not follow the same ecological patterns as terrestrial and lotic habitats (reduced taxonomic richness) in urban environments; in contrast, they support high taxonomic richness and contribute significantly to regional faunal diversity. Individual cities are complex structural mosaics which evolve over long periods of time and are managed in diverse ways. This facilitates the development of a wide range of environmental conditions and habitat niches in urban ponds which can promote greater heterogeneity between pond communities at larger scales. Ponds provide an opportunity for managers and environmental regulators to conserve and enhance freshwater biodiversity in urbanized landscapes whilst also facilitating key ecosystem services including storm water storage and water treatment.     

Habitat structure determines spider diversity in highland ponds

Wetlands (e.g. ponds, meadows) can be found in many landscapes, playing an important role in maintaining regional biodiversity and supporting heterogeneous communities. Spiders are diversified predators that are highly influenced by changes in plant community structure, heterogeneous habitats sustain high spider diversity and abundance. We investigated the characteristics of spider biodiversity in ponds with different habitat structures, by examining patterns across habitats of ponds with different vegetation levels. Sampling took place in four occasions over a year. We compared spider abundance, species richness and composition among ponds including distinct vegetation variables, related to life form, type of leaves, coverage and height. Overall 1174 individuals (194 adults) of 11 families and 37 morphospecies were sampled. We found mostly expected differences in the manner that communities were structured between different habitats. Thus, higher variability of abundance was explained for higher habitat structure of ponds. We also found differences in species composition between ponds with low emergent vegetation and higher habitat structures. Additionaly, spiders were consistently structured more by turnover than nestedness components, with a greater beta diversity of web-builders. Our results suggest varying levels of habitat structures and species substitution shape pond spider communities, depending on habitat heterogeneity and spider guild. Those findings demonstrate the clear role of spatial habitat structure, with more spider species preferring to build webs or actively hunt at vegetated environments on ponds.     

How to Maximally Support Local and Regional Biodiversity in Applied Conservation? Insights from Pond Management

Biodiversity and nature values in anthropogenic landscapes often depend on land use practices and management. Evaluations of the association between management and biodiversity remain, however, comparatively scarce, especially in aquatic systems. Furthermore, studies also tend to focus on a limited set of organism groups at the local scale, whereas a multi-group approach at the landscape scale is to be preferred. This study aims to investigate the effect of pond management on the diversity of multiple aquatic organism groups (e.g. phytoplankton, zooplankton, several groups of macro-invertebrates, submerged and emergent macrophytes) at local and regional spatial scales. For this purpose, we performed a field study of 39 shallow man-made ponds representing five different management types. Our results indicate that fish stock management and periodic pond drainage are crucial drivers of pond biodiversity. Furthermore, this study provides insight in how the management of eutrophied ponds can contribute to aquatic biodiversity. A combination of regular draining of ponds with efforts to keep ponds free of fish seems to be highly beneficial for the biodiversity of many groups of aquatic organisms at local and regional scales. Regular draining combined with a stocking of fish at low biomass is also preferable to infrequent draining and lack of fish stock control. These insights are essential for the development of conservation programs that aim long-term maintenance of regional biodiversity in pond areas across Europe.     

Local and Landscape Factors Driving the Structure of Tropical Anuran Communities: Do Ephemeral Ponds have a Nested Pattern?

The sets of species in animal and plant communities often comprise nested subsets of the species in broader communities. Although most mechanisms causing nested patterns are known and have been demonstrated for different environments and taxa, how amphibian communities are structured in ephemeral ponds in tropical disturbed landscapes remains unknown. We investigated if pond size, duration, presence of trees (local factors), and the proportion of forest cover surrounding ponds (landscape factor) affect anuran species richness and composition, and if pond assemblages showed a nested pattern. We sampled 11 ephemeral ponds in a pasture matrix near a large Atlantic Forest remnant in Brazil and measured local and landscape variables inside two buffer zones around each pond (100 and 500 m). We marked 1514 individuals from 23 anuran species, and found that richness in ponds ranged from 3–14 species. Both local and landscape factors explained frog species richness in the sampled ponds, and seemed to affect community composition. Frog communities occurred in a non‐nested pattern, contrary to our expectations: species found in poor subsets were not found in larger, more complex ponds. Local and landscape characteristics create a variety of environments in ephemeral ponds, even in impoverished ones; these characteristics restrict pond occupancy for some species, and result in a non‐nested pattern.