PERIPHYTIC DIATOM ASSEMBLAGES FROM HIGH ARCTIC PONDS1

Epiphytic, epilithic, and surface sediment diatom assemblages were identified and enumerated from 35 study ponds on CapeHerschel (78°37″N, 74°42″W), east-central Ellesmere Island, Canada. All the sites are shallow (maximum depth <2 m), clear, oligotrophic, and freshwater. The ponds freeze completely for 10 months of the year. Major ion concentrations are relatively similar among the 35 sites, although environmental gradients exist. Over 130 diatom taxa from 28 genera were identified in the periphyton samples. Marked differences in species composition were evident among the ponds. Moreover, many of the diatoms exhibited varying degrees of microhabitat specificity. Variance partitioning by canonical correspondence analysis showed that 26% of the total variance exhibited by diatom species composition could be accounted for by the measured environmental variables (i.e. 10.2% by habitat and 15.8% by water chemistry). Pondwater alkalinity best explained the distribution of taxa, and weighted averaging regression and calibration were used to develop a transfer function to infer pondwater alkalinity from the diatom assemblages. Other important environmental variables included [Na⁺] for the epilithic and [SiO₂] for the epiphytic assemblages.     

Stream epilithic, epipelic and epiphytic diatoms: habitat fidelity and use in biomonitoring

We compared the use of epilithic, epiphytic, and epipelic diatom communities in stream biomonitoring by investigating species composition and relationships with measured water quality variables in two tributaries of the Grand River, Ontario, Canada. Although ordination showed some separation of the epilithon from other habitats, clear habitat preferences and seasonality were not identified. Canonical correspondence analysis showed that measured water quality variables explained the major gradients in the diatom data for all three habitats. The diatoms from each habitat were strongly related to alkalinity, suspended solids, biological oxygen demand and conductivity, and in addition, epipelic and epiphytic diatoms showed significant relationships with total phosphorus. It was concluded that although some species were more abundant in one habitat than the others, the community structure of the epilithic, epiphytic and epipelic habitats from these streams was not consistently different. The results indicate no apparent benefit to sampling discrete habitats for water quality monitoring using diatoms, however, the best relationship are obtained using the sum of the diatom data from all three habitats.     

Fish assemblages in temporary ponds adjacent to 'terra-firme' streams in Central Amazonia

1. The effect of habitat structural features and physicochemical characteristics of the water on the composition and richness of fish assemblages in temporary ponds near streams were examined at three spatial scales: among ponds, among streams and between drainage basins, in a ‘terra‐firme’ (not subject to long‐term flooding) forest reserve in Central Amazonia. 2. The fish assemblage in temporary ponds was composed of subsets of 18 small‐bodied species widely distributed in the reserve. The assemblages had a nested subset structure, where smaller ponds contained subgroups of the species found in larger ponds. 3. Species composition and richness in temporary ponds were similar between drainage basins, although the fish assemblages in streams differed between basins. 4. Fish assemblage structure was influenced by local factors related to habitat structure, such as pond area and depth, canopy cover and hydroperiod. Physicochemical characteristics of the water in the ponds were similar between drainage basins and had little detectable effect on the structure of pond fish assemblages. 5. No correspondence was found between the composition, richness or abundance of fishes in the ponds and in stretches of the streams adjacent to the ponds. Therefore, it is not possible to predict the composition of these temporary pond fish assemblages from the fish assemblages found in adjacent streams.     

Distribution of epipelic diatoms in artificial fishponds along environmental and spatial gradients

Although epipelic diatoms play a key role in primary production of many ecosystems, many aspects of their biodiversity, ecology and geographical distribution are poorly understood. The present study is based on sampling of 45 man-made fishponds in the Czech Republic covering an environmental gradient from oligo/dystrophic highland ponds within protected areas to the eutrophic/hypertrophic lowland ponds used for intensive fish production. Diatom distribution patterns assessed using biomass and species composition variables were assessed along environmental and geographical gradients. In total, 185 epipelic diatom taxa were found in the investigated samples. The differences in species composition between sites were correlated with environmental parameters, but not with the geographic distance of the localities. This pattern might suggest that niche-based control, rather than the effect of dispersal limitation, is the main driving force in the species composition of epipelic diatoms in fishponds. The alpha-diversity of sites correlated with altitude, nitrogen and chlorophyll a concentrations but did not correlate with the area of the ponds. The significant relationships between local abundance of species and their regional occupancy were very similar to previous studies of diatoms in boreal streams. In addition, these data concur with patterns known for multicellular organisms suggesting that in this respect diatoms may not differ from groups of organisms with larger body sizes. Handling editor: J. Padisak     

Freshwater diatom and macroinvertebrate diversity of coastal permanent ponds along a gradient of human impact in a Mediterranean eco-region

Mediterranean coastal areas are characterised by heavily transformed landscapes and an ever-increasing number of ponds are subjected to strong alterations. Although benthic diatoms and macroinvertebrates are widely used as indicators in freshwater ecosystems, little is still known about the diatom communities of lowland freshwater ponds in the Mediterranean region, and, furthermore, there are few macroinvertebrate-based methods to assess their ecological quality, especially in Italy. This article undertakes an analysis of benthic diatom and macroinvertebrate communities of permanent freshwater ponds, selected along a gradient of anthropogenic pressures, to identify community indicators (taxa and/or metrics) useful to evaluate the effect of human impacts. A series of 21 ponds were sampled along Tyrrhenian coast in central Italy. Five of these ponds, in a good conservations status and surrounded by woodland were selected as ‘reference sites’ for macroinvertebrates and epipelic diatoms. The remaining sixteen ponds were located in an agricultural landscape subject to different levels of human impact. The total number of macroinvertebrate taxa found in each pond was significantly higher in reference sites than in both the intermediate and heavily degraded ones, whereas the diatom species richness did not result in a good community variable to evaluate the pond ecological quality. The analysis revealed a substantial difference among the compositions of diatom communities between reference ponds and degraded ponds. The former were characterised by the presence of several species belonging to genera, such as Pinnularia sp., Eunotia sp., Stauroneis sp., Neidium sp., all of which were mostly absent from degraded ponds. Furthermore, the taxonomic richnesses of some macroinvetebrate groups (Odonata, Ephemeroptera, Trichoptera, Coleoptera), and taxa composition attributes of macroinvertebrate communities (total abundance, percentages of top three dominant taxa, percentages of Pleidae, Ancylidae, Hirudinea, Hydracarina) significantly correlated with variables linked with anthropogenic pressures. The results of the investigation suggested that diatoms tended more to reflect water chemistry through changes in community structure, whereas invertebrates responded to physical habitat changes primarily through changes in taxonomic richness. The methodologies developed for the analysis of freshwater benthic diatom and macroinvertebrate communities may have a considerable potential as a tool for assessing the ecological status of this type of water body, complying with the European Union Water Framework Directive 2000/60/EC. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. 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     

Diatoms as indicators of stream quality in the Kathmandu Valley and Middle Hills of Nepal and India

1. Diatoms are recognised as indicators in temperate streams, but only recently have assessments begun of their value in indicating stream quality in the tropics and sub‐tropics. Here, we extend previous studies by assessing stream diatom assemblages in relation to water quality and habitat character in the Kathmandu Valley, and in the Middle Hills of Nepal and northern India. We also assessed whether the U.K. Trophic Diatom Index (TDI) was sufficiently portable to reveal pollution in Himalayan rivers. In the more urbanised and highly agricultural Kathmandu Valley, we compared diatom response to water quality classes indicated by a local invertebrate index, the Nepalese Biotic Score (NEPBIOS). 2. Thirty and 53 streams in the Kathmandu Valley (2000) and Middle Hills (1994–96), respectively, were sampled in October and November during stable flows following the monsoon. Diatoms were collected in riffles, water samples taken for chemical analysis, and habitat character of the stream channel, bank and catchment assessed using river habitat surveys. In the Kathmandu Valley, macroinvertebrates were collected by kick‐sampling. 3. In total, 113 diatom taxa were found in the Kathmandu Valley streams and 106 in the Middle Hills. Of 168 taxa recorded, 62 occurred only in the Kathmandu Valley, 56 only in the Middle Hills and 50 were common to both areas. Most taxa found only in the Kathmandu Valley belonged to the genus Navicula while most taxa confined to the Middle Hills were Achnanthes, Fragilaria and Gomphonema. 4. In the Kathmandu Valley, richness and diversity increased significantly with K, Cl, SO₄ and NO₃, but declined significantly with Al, Fe, surfactants and phenols. Richness here also varied with habitat structure, being lowest in fast flowing, shaded streams with coarse substrata in forested catchments. In all streams combined, richness increased significantly with Si, Na and PO₄, but declined significantly with increasing pH, Ca and Mg. 5. Diatom assemblage composition in the Kathmandu Valley strongly reflected water chemistry as revealed by cations (K, Na, Mg, Ca), anions (Cl, SO₄), nutrients (NO₃, PO₄, Si), and also substratum composition, flow character and catchment land use. The commonest taxa in base‐poor forested catchments were Achnanthes siamlinearis, A. subhudsonis, A. undata and an unidentified Gomphonema species; Cocconeis placentula and Navicula minima in agricultural catchments; and Mayamaea atomus var. alcimonica, M. atomus var. permitis, and Nitzschia palea at polluted sites near settlements. Diatom assemblages in none‐agricultural catchments of the Kathmandu Valley and Middle Hills were similar, but they contrasted strongly between urban or agricultural catchments of the Kathmandu Valley and the less intensively farmed catchments of the Middle Hills. 6. In keeping with variations in assemblage composition, most streams in the Kathmandu Valley had higher TDI values (33–87, median = 64) and more pollution tolerant taxa (0–78%, median = 16) than streams in the Middle Hills (25–82, median 45, 0–26%, median = 2). TDI values correlated significantly with measured PO₄, Si, and Na concentrations in the Kathmandu Valley, and with Si and Na concentrations in the Middle Hills. There was some consistency between water quality classes revealed by NEPBIOS and diatoms, but also some contrast. Water quality class I–II sites had lower TDI values and were less species rich than water quality II sites, however, there were no significant differences in detrended correspondence analysis (DCA) assemblage scores and relative abundances of pollution tolerant taxa between NEPBIOS classes. 7. While diatoms in the Middle Hills indicate unpolluted or only mildly enriched conditions, they reveal pronounced eutrophication and organic pollution in the densely populated Kathmandu Valley. In addition, diatoms appear to respond to altered habitats in rural agricultural and urban areas. As demands on water resources in this region are likely to increase, we advocate the continued development of diatoms as indicators using methods based on what appear to be consistent responses in the TDI between Europe and the Himalaya.     

Patterns of Assemblage Structure Indicate a Broader Conservation Potential of Focal Amphibians for Pond Management

Small freshwater ponds host diverse and vulnerable biotic assemblages but relatively few conspicuous, specially protected taxa. In Europe, the amphibians Triturus cristatus and Pelobates fuscus are among a few species whose populations have been successfully restored using pond restoration and management activities at the landscape scale. In this study, we explored whether the ponds constructed for those two target species have wider conservation significance, particularly for other species of conservation concern. We recorded the occurrence of amphibians and selected aquatic macro-invertebrates (dragonflies; damselflies; diving beetles; water scavenger beetles) in 66 ponds specially constructed for amphibians (up to 8 years post construction) and, for comparison, in 100 man-made ponds (created by local people for cattle or garden watering, peat excavation, etc.) and 65 natural ponds in Estonia. We analysed nestedness of the species assemblages and its dependence on the environment, and described the co-occurrence patterns between the target amphibians and other aquatic species. The assemblages in all ponds were significantly nested, but the environmental determinants of nestedness and co-occurrence of particular species differed among pond types. Constructed ponds were most species-rich irrespective of the presence of the target species; however, T. cristatus was frequent in those ponds and rare elsewhere, and it showed nested patterns in every type of pond. We thus conclude that pond construction for the protected amphibians can serve broader habitat conservation aims in the short term. However, the heterogeneity and inconsistent presence of species of conservation concern observed in other types of ponds implies that long-term perspectives on pond management require more explicit consideration of different habitat and biodiversity values. We also highlight nestedness analysis as a tool that can be used for the practical task of selecting focal species for habitat conservation.     

Determinant landscape‐scale factors on pond odonate assemblages

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Phytoplankton assemblages and community structure in tropical temporary freshwater ponds in sub‐Saharan Africa1

Anthropogenic and climatic factors are important determinants of algal distribution in aquatic systems. This study aimed to identify temporary pond‐groups of phytoplankton assemblages and to establish the interactions between environmental variables and phytoplankton structure. Phytoplankton samples were collected and preserved with 5% formalin; water samples for chemical analysis were taken in August and September 2007, 2008, and 2009 in 86 ponds randomly selected in the Sahelian sector and the Sudanian sector (protected and unprotected areas) of Burkina Faso. Plankton species were examined using light microscopy and identified using standard methods. A Fuchs‐Rosenthal chamber was used for algal cell counting. NMDS ordination, indicator species analysis and canonical analysis were performed using Pc‐Ord and CANOCO. Kruskal–Wallis and Mann–Whitney U‐tests using the software Statistica were performed to compare parameters between pond‐groups. Three pond‐groups were identified: the Sahelian pond‐group, dominated by Lyngbya martensiana and Pseudanabaena constricta; the protected area pond‐group, dominated by Euglena caudata and Trachelomonas raciborskii; and the unprotected area pond‐group, dominated by Closterium venus and Euglena proxima. At P < 0.05, species composition and abundance in algal groups were mostly associated with nitrate, pH, dissolved oxygen, and conductivity. The Sahelian and the Sudanian sectors were different in pH, water transparency, and species richness. Univariate and multivariate analyses illustrate that variations in the physicochemical properties of water and algal structure followed climatic and anthropogenic gradients. The classification of ponds into algal associations demonstrated that algal assemblages may be used as reliable indicators of habitat conditions.     

The chemistry of surface water in prairie ponds

Water analyses from 80 small prairie ponds, 0.17 to 89.8 hectares, in Manitoba and Saskatchewan between 1967 to 1972 exhibited two basic ionic dominance patterns HCO₃ > SO₄ > Cl and SO₄ > HCO₃ > Cl. The order of SO₄ and Cl were reversed in 40 percent of the bicarbonate ponds below 500 µmhos/cm. At salinities above 12,000 µmhos/cm, Cl exceeds SO₄ in several wetlands. Temporary wetlands were characterised by Ca > K > Mg > Na / HCO₃ > Cl > SO₄, semi-permanent ponds Mg > Ca > Na > K / SO₄ > HCO₃ > Cl while the permanent pond structure was Ca > Mg > Na > K / HCO₃ > SO₄ > Cl.Conductivities of the wetlands studied ranged from 47 to 23,000 µmhos / cm.Seasonal changes in salinity varied within and between pond types as well as from year to year. The average salinity increase within season in temporary ponds was 67 percent, 63 percent in semi-permanent ponds and 20 percent for permanent ponds. These changes were affected by evaporation, transpiration, see-page and precipitation patterns. Ionic dominance patterns did not change within a season although Mg, K and HCO₃ increased at higher rates than Ca, Na, CI and SO₄.Temporary wetlands are slightly acidic, averaging pH 6.8 while semi-permanent and permanent ponds were alkaline, pH range 7.1 to 9.2. No stratification of pH with depth and minimal diurnal variation was recorded.At two study areas, Bradwell and St. Denis fhe following ranges (micrograms/litre) were recorded: 3 to 630 PO₄-P, 10 to 650 NO₃-N, 5 to 630 TDFe, 1 to 13 TDCu and 1 to 27 TDZn. Colour was 5 to 190 Hazen units at St. Denis and 10 to 110 for Bradwell.Two herbicides, 2,4-D and 2,4,5-T were detected at levels of 4 to 111 and 1.4 to 13.5 micrograms/litre, respectively, from 15 ponds at St. Denis.     

PATTERNS OF EPIPELIC ALGAL DISTRIBUTION IN AN ACIDIC ADIRONDACK LAKE1

The biovolume and species composition of epipelic algae along sediment depth gradients were sampled seasonally in an acidic oligotrophic lake in the Adirondack Park in New York State. The epipelic algal community of Woods Lake (Herkimer Co., NY) was dominated by diatoms and cyanobacteria. Distinct depth zonation patterns of community composition were evident. Total algal biovolume increased with depth due to a dense cyanobacterial mat on the sediments in deeper water (5–8 m). This mat was dominated by a single species of cyanobacteria, Hapalosiphon pumilus (Kütz.) Kirchner, which accounted for the late summer maximum in total biovolume at 7 m. The shallower (1–4 m) epipelic communities were dominated by diatoms, which showed a spring maximum in total biovolume and were dominated by Fragilaria acidobiontica Charles, Navicula tenuicephala Hust. and N. subtilissima Cl.     

Promoting dragonfly diversity in cities: major determinants and implications for urban pond design

Urbanisation is increasing and it is essential to integrate biodiversity into the spatial planning of urban areas. This requires deeper understanding of biodiversity patterns in cities. We investigated which habitat variables are major determinants of dragonfly diversity and species assemblage structure in the municipal area of Dortmund (Germany). We sampled dragonfly larvae in 33 ponds situated in city parks, commercial, residential and agricultural areas. We recorded 30 autochthonous dragonfly species with species richness ranging from zero to 17. Additionally, we surveyed a set of environmental variables including habitat size, water level, pond structures and vegetation as well as surrounding landscape and potential disturbances like waterfowl and fish. Multivariate methods were used to identify the major determinants of dragonfly diversity, abundance and assemblage structure. Analysis indicated that diversity of aquatic and terrestrial vegetation affected dragonfly diversity positively. City park ponds had low diversity, but Ischnura elegans was obviously promoted by the specific park pond conditions, including high waterfowl density. We found five assemblages mostly determined by generalistic species which were related to different pond types. Moderately disturbed ruderal and pioneer ponds in residential and agricultural areas also contained increased numbers of rare species. Our results indicate that urban ponds may have a great value for maintaining biodiversity, but various disturbances have negative impact. To promote urban biodiversity we suggest a natural design of well-vegetated ponds as well as a high diversity of different pond types and particularly a more-natural redesign of city park ponds.     

Determining diatom ecotones and their relationship to terrestrial ecoregion designations in the central Canadian Arctic Islands

Ecotones are key areas for the detection of global change because many are predicted to move with shifts in climate. Prince of Wales Island, in the Canadian Arctic Archipelago, spans the transition between mid‐ to high‐Arctic ecoregions. We analyzed limnological variables and recent diatom assemblages from its lakes and ponds to determine if assemblages reflected this ecotone. Limnological gradients were short, and water chemistry explained 20.0% of diatom variance in a redundancy analysis (RDA), driven primarily by dissolved organic carbon, Ca and SO₄. Most taxa were small, benthic forms; key taxa such as planktonic Cyclotella species were restricted to the warmer, southern portion of the study area, while benthic Staurosirella were associated with larger, ice‐dominated lakes. Nonetheless, there were no significant changes in diatom assemblages across the mid‐ to high‐Arctic ecoregion boundary. We combined our data set with one from nearby Cornwallis Island to expand the study area and lengthen its environmental gradients. Within this expanded data set, 40.6% of the diatom variance was explained by a combination of water chemistry and geographic variables, and significant relationships were revealed between diatom distributions and key limnological variables, including pH, specific conductivity, and chl‐a. Using principal coordinates analysis, we estimated community turnover with latitude and applied piecewise linear regression to determine diatom ecotone positions. A pronounced transition was present between Prince of Wales Island and the colder, more northerly Cornwallis Island. These data will be important in detecting any future northward ecotone movement in response to predicted Arctic climate warming in this highly sensitive region.     

Anuran tadpole assemblages in riparian areas of the Middle Paraná River, Argentina

We investigated habitat variables influencing the species richness and composition of anuran tadpole assemblages in ponds from riparian areas of the Middle Paraná River. Tadpoles were collected at seven ponds that differed in hydroperiod and 10 habitat variables (water temperature, pH, conductivity, dissolved oxygen, turbidity, depth, size, time of isolation, macrophyte richness, and level of natural or anthropic disturbances) during a 5 year period. The presence/absence of potential tadpole predators was also recorded. Although we did not examine tadpole diets, we categorized anurans into ecomorphological guilds. We found that dissolved oxygen, maximum depth, pond size, macrophyte richness, and disturbances were significantly related to tadpole species richness. We also found that the richness of potential tadpole predator increased with longer pond hydroperiod. Thus, the number of tadpole species was higher in temporary and semi-permanent ponds without potential tadpole predators. The results of our study provide the first quantitative data on the tadpole assemblages in ponds associated with riparian areas of the Middle Paraná River Floodplain based on multi-year intensive sampling, a finding of both ecological interest and practical significance for future conservation management of anurans of Paraná River ecosystems.     

PERIPHYTIC DIATOM ASSEMBLAGES FROM ULTRA‐OLIGOTROPHIC AND UV TRANSPARENT LAKES AND PONDS ON VICTORIA ISLAND AND COMPARISONS WITH OTHER DIATOM SURVEYS IN THE CANADIAN ARCTIC1

Periphytic diatoms are potentially powerful indicators of environmental change in climatically‐sensitive high latitude regions. However, only a few studies have examined their taxonomic and ecological characteristics. We identified and enumerated diatom assemblages from sediment, rock, and moss habitats in 34 ultra‐oligotrophic and highly transparent lakes and ponds on Victoria Island, Arctic Canada. The similar limnological characteristics of the sites allowed us to examine the influence of habitat, independent of water chemistry, on the diatom assemblages. As is typical in shallow arctic water bodies, benthic taxa, including species of Achnanthes, Caloneis, Cymbella, Navicula, and Nitzschia, were most widely represented. Minor gradients in our measured environmental variables did not significantly explain any variance in diatom species, but there were marked differences in diatom assemblages among sites. Pond ephemerality seems to explain some diatom variation, because aerophilic taxa such as Achnanthes kryophila Petersen and A. marginulata Grunow were dominant in shallow sites that had undergone appreciable reductions in volume. We identified several taxa that exhibited strong habitat preferences to sediment, moss, or rock substrates and also found significant differences (P < 0.01) in diatom composition among the three habitats. In comparisons with three similar diatom surveys extending over 1200 km of latitude, we determined that surface sediment assemblages differed significantly (P < 0.001) among all regions examined. Diatom species diversity was inversely related to latitude, a result likely explained by differences in the lengths of growing seasons. These data contribute important ecological information on diatom assemblages in arctic regions and will aid in the interpretation of environmental changes in biomonitoring and paleolimnological studies.     

Aquatic macrophyte composition in relation to environmental factors of irrigation ponds around Lake Shinji,Shimane, Japan

A comparative study of aquatic vegetation of 149 irrigation ponds in the surrounding area of Lake Shinji, Shimane Prefecture, Japan, was done to document the present status of aquatic flora and water chemistry. In addition, influence of 17 environmental factors on the between-pond variation in aquatic macrophyte composition was assessed by using detrended correspondence analysis (DCA). A total of 38 taxa were recorded, and the most frequent taxon was Trapa spp. (>50%). Number of taxa per pond ranged from 1 to 14 and mean number was 4.1. Floristic composition was primarily related to variation of the factors such as conductivity, Mg, Ca, Na, alkalinity, altitude, pH and depth. In contrast, no significant correlations were found with total P, PO₄-P, transparency, COD, ignition loss of bottom soil, Mn and Fe. Of the 33 significant species associations between 19 species with more than 5% frequency occurrence, 28 were positive and the remaining 5 were negative. All of these negative associations involved Trapa spp., and not only water chemistry but some other factors like competition and bottom soil preference were assumed to influence species associations.Abbreviations (DCA) Detrended Correspondence Analysis     

The physicochemistry of some dune ponds on the Outer Banks,North Carolina

A survey of the chemical composition of five coastal dune ponds on the Outer Banks, North Carolina, showed the ponds to be more similar to underlying groundwater than to dilute seawater or average river water. With a mean total ionic content of 3.14 mmol l^–1 the ponds were decidedly fresh. Variations in chemistry between the ponds resulted from physiographic association with leached or unleached dunes, and from different soil types in the pond basins. Near isothermal conditions were found in all but one pond. Oxygen levels were reduced at depth in every pond (10 to 25% saturation). Comparative data show the influences on major ion chemistry in these ponds to be substantially different from those of some other coastal dune waters.     

Urban amphibian assemblages as metacommunities

1. Urban ecosystems are expanding throughout the world, and urban ecology is attracting increasing research interest. Some authors have questioned the value of existing ecological theories for understanding the processes and consequences of urbanization. 2. In order to assess the applicability of metacommunity theory to urban systems, I evaluated three assumptions that underlie the theory - the effect of patch area, the effect of patch isolation, and species-environment relations - using data on assemblages of pond-breeding amphibians in the Greater Melbourne area of Australia. I also assessed the relative impact of habitat fragmentation, habitat isolation, and changes to habitat quality on these assemblages. 3. Poisson regression modelling provided support for an important increase in species richness with patch area (pond size) and a decrease in species richness with increasing patch isolation, as measured by surrounding road cover. Holding all other variables constant, species richness was predicted to be 2.8-5.5 times higher at the largest pond than at the smallest, while the most isolated pond was predicted to have 12-19% of the species richness of the least isolated pond. Thus, the data were consistent with the first two assumptions of metacommunity theory evaluated. 4. The quality of habitat at a pond was also important, with a predicted 44-56% decrease in the number of species detected at ponds with a surrounding vertical wall compared with those with a gently sloping bank. This demonstrates that environmental differences between habitat patches were also influencing amphibian assemblages, providing support for the species-sorting and/or mass-effect perspectives of metacommunity theory. 5. Without management intervention, urbanization may lead to a reduction in the number of amphibian species persisting in urban ponds, particularly where increasing isolation of ponds by roads and associated infrastructure reduces the probability of re-colonization following local extinction. Journal of Animal Ecology (2006) 75, 757-764 doi: 10.1111/j.1365-2656.2006.01096.x.     

Foraging tactics in alternative heterochronic salamander morphs: trophic quality of ponds matters more than water permanency

1. In lentic freshwater habitats, the composition of animal assemblages shifts along a gradient from temporary to permanent basins. When habitats with different degrees of permanence are at the scale of the home range of species, they constitute alternatives in terms of energy acquisition through feeding. 2. In this context, previous studies showed an advantage of metamorphic over paedomorphic tiger salamanders (Ambystoma tigrinum) in temporary ponds which are only available to metamorphs. The aim of this study was to establish whether salamanders obtain similar benefits in ponds that do not differ in water permanence and whether salamanders shifted from detrimental to advantageous ponds. To this end, we determined the feeding habits, body condition and movement patterns of the two morphs in a complex of four permanent and four temporary ponds. 3. Consistent with previous studies, metamorphs consumed higher‐quality diets than paedomorphs in term of energy intake. However, these differences occurred because metamorphs consumed fairy shrimp in a single temporary pond. Individual movement patterns confirmed that most of the metamorphs used different aquatic habitats both within and between years and that most of them moved from permanent ponds for breeding towards the most profitable temporary pond in terms of foraging. 4. These results indicate that habitat selection by salamanders is optimal in term of energy intake in metamorphs that use high quality ponds independently of hydroperiod. It seems that both spatial and temporal variation can influence the relative foraging success of each morph.