Colonisation of experimentally immersed wood in south eastern Australia: responses of feeding groups to changes in riparian vegetation

We investigated macroinvertebrate abundance and functional feeding groups colonising experimentally-positioned woody substrates of different species in streams with three different riparian vegetation types. Native Eucalyptus forest formed a dense closed canopy over our streams; introduced (exotic, alien) pine plantation forest did not fully shade the streams, and grassland streams were completely open, although with woody riparian vegetation well upstream of our sites. Macroinvertebrate assemblages varied taxonomically and functionally with both wood species and riparian vegetation composition. Two specialist feeding groups responded clearly to riparian vegetation: wood gougers were most common in forested streams, and algal grazers in more open streams. Gougers colonised native Eucalyptus wood in preference to alien species. Other feeding groups responses showed complex interactions between vegetation and wood type. Our results indicate the importance of sampling appropriate substrates when assessing questions of this type – if seeking shifts in functional organisation, the substrates on which the feeding groups of interest occur must be sampled. The composition of the riparian strip may influence xylophilous communities as much as the structure (i.e. whether closed or open).     

Structure of herbaceous plant assemblages in a forested riparian landscape

We assessed patterns of herbaceous and woody species richness, plant-environment interactions, and correspondence between the herb and tree layer in a riparian landscape (the Ozark National Scenic Riverways, Missouri, USA). A total of 269 herb and 70 tree species were identified on 94 sample plots. Gradient analysis revealed that environmental variables and vegetation were influenced by a strong elevation gradient. However, high variability in environmental variables (pH, elevation, slope, sand, clay, organic matter) indicated a high level of substrate heterogeneity across the riparian landscape. We were unable to predict the composition of the herb understory from the canopy trees with any detailed accuracy and no clear characterization of herb species assemblages was found using cluster analysis or ecological land type (ELT) classifications. Canonical correspondence analysis (CCA) results for both tree and herb plots showed that elevation (height above river) and pH were the dominant environmental gradients influencing vegetation patterns on the first CCA axis while soil particle size exhibited the strongest correlation with the second CCA axis. Secondary gradients of importance included slope, soil container capacity, and organic matter. No significant linear or quadratic correlation was found between elevation and herb or woody species richness. Environmental variables alone or in combination, were weak predictors of herb and woody species richness, despite the patterns observed in the gradient analysis and the correlations observed in the CCA results. Ecotonal analysis showed that the herb layer exhibited a high species replacement rate at the lower elevations most susceptible to flooding (0–3 m). Above the flooding zone, there was more or less continuous species replacement, suggesting the presence of a gradual ecotone/ecocline. The tree layer exhibited much stronger discontinuities than the herb layer in the lower elevations along the height gradient (0–10 m). Recognizing the limitations of classification techniques for riparian herb assemblages and the importance of scale and heterogeneity in vegetation layers is especially important in light of mandates to preserve, protect, and manage for plant diversity.     

MULTIVARIATE ANALYSIS OF PERIPHYTON ASSEMBLAGES IN RELATION TO ENVIRONMENTAL GRADIENTS IN COLORADO ROCKY MOUNTAIN STREAMS 1

We assessed relationships between chemical and physical characteristics and periphyton assemblages in stream reaches of the mineral belt in the Southern Rockies ecoregion of Colorado, United States. Using canonical ordination analyses, we contrasted results wherein assemblage structure was assessed using community metrics or species abundances. Our objectives were to identify community metrics or individual species diagnostic of the primary environmental stressors in these streams, to compare the sensitivity of these two approaches to determining the primary stressors, and to determine how these approaches may be used to differentiate the effects of these environmental stressors from other gradients. For periphyton metrics, the first axis extracted by redundancy analysis correlated with total phosphorus, substrate coarseness and embeddedness, and riparian vegetation condition, whereas the second axis correlated with dissolved metals. For species abundances, the three axes extracted by canonical correspondence analysis (CCA) were correlated with (1) stream size and types of in‐stream habitats; (2) total phosphorus, dissolved ions, and riparian disturbance by agriculture; and (3) sediment coarseness and embeddedness and riparian vegetation condition. Concentrations of dissolved metals were not correlated with the CCA axes. Analyses of species abundances were sensitive to effects associated with nutrients, substrates, and riparian vegetation, whereas analyses of periphyton metrics were sensitive not only to these nutrient and physical habitat effects but also to toxicological effects associated with metals. As a result, the analyses of periphyton metrics may be used to identify which metrics would be useful for a periphyton index of biotic integrity and would also be individually diagnostic of the larger scale stressors in these streams, nutrient, substrate, and riparian vegetation effects of livestock grazing and increased metal concentrations associated with metal mining.     

Blackfly (Diptera, Simuliidae) communities and species richness estimation in Carpathian montane streams

The present work gives the result of blackfly fauna research of the Slovenský raj (West Carpathians, Slovakia). Our aim was to describe the composition of blackfly communities, find indicator species for communities, describe environmental factors affecting communities and determine the potential changes in species richness. Research was carried out in 2007 and 2008. The presence of 22 species of blackflies was confirmed at 20 sites in the area of Slovenský raj. 12 species were recorded for the first time in this area. The potential for further increase in diversity was calculated by a nonparametric estimation of species richness. Two main groups of sites with their typical blackflies communities were indentified using a TWINSPAN analysis. The presence of Simulium ornatum, S. variegatum and S. argyreatum was typical in larger streams in broad valleys. The absence or low abundance of these species was typical for smaller streams in canyons. Based on the species composition of blackflies communities, we identified 6 groups of sites: 1. anthropogenically disturbed submountain rivers (typical species: Simulium ornatum, S. reptans, S. equinum), 2. undisturbed metarhithral (typical species: Simulium bertrandi, S. codreanui, S. costatum, S. vernum, S. argenteostriatum, S. degrangei, S. argyreatum, S. variegatum), 3. undisturbed hyporhithral (typical species: Simulium trifasciatum, S. tuberosum), 4. undisturbed epirhithral (typical species: Prosimulium hirtipes, P. rufipes), 5. hypocrenal (typical species: Simulium cryophilum, S. monticola) and 6. anthropogenically disturbed epirhithral (typical species: Simulium brevidens, S. maximum). The most important environmental factors explaining differences in species composition like altitude, flow speed, pH, conductivity, oxygen saturation, sulphates concentration and presence of riparian vegetation were identified by the CCA analysis.     

Mayfly bioindicator thresholds for several anthropogenic disturbances in neotropical savanna streams

Anthropogenic disturbances are widely recognized as major threats to terrestrial and aquatic biodiversity worldwide, including areas located in non-forest ecosystems. Headwater streams in the neotropical savanna are severely threatened by large-scale landscape changes that degrade local habitat characteristics and lead to biodiversity loss. The objective of our study was to evaluate Ephemeroptera assemblages as bioindicators of catchment land use and cover, local streambed and riparian vegetation conditions, and instream water quality. To do so, we sampled mayfly nymphs in 184 stream sites across a broad disturbance gradient in four hydrologic units of the Brazilian neotropical savanna. We selected seven metrics without significant co-variation with natural variability: % catchment urban, riparian vegetation condition index (RCOND), human disturbances of the stream channel and riparian zone (W1_HALL), substrate mean embeddedness (XEMBED), dissolved oxygen (mg L⁻¹), pH, and total phosphorus (mg L⁻¹). We ran threshold indicator taxa analysis (TITAN) for each disturbance metric to detect change points in mayfly genera responses (whether sensitive or tolerant) and assemblage turnover pattern. TITAN showed that 20 of the 39 genera found were robust bioindicators (based on purity and reliability values >0.95), sixteen of them being sensitive to increased disturbance. The most sensitive genera were Tricorythopsis (Leptohyphidae) and Camelobaetidius (Baetidae), showing decreased abundance to most disturbance metrics. We found a turnover pattern of mayfly genera in response to W1_HALL in a narrow variation range. For total phosphorus, the benchmark value defined in Brazilian Federal Legislation is higher than the turnover threshold of several mayfly genera. This indicates that we will lose many sensitive genera even within the limits imposed by national environmental legislation. The indicator taxa approach, based on multiple taxa rather than univariate metrics or single indicator species, demonstrates the value of quantitative ecological information for conserving and managing freshwater ecosystems globally.     

Effects of riparian vegetation width and substrate type on riffle beetle community structure

Riffle beetle community structure is influenced by the preservation condition of stream riparian vegetation. Though, the width of riparian vegetation required to ensure conservation of stream insect communities is still controversial. Effects of alterations in riparian vegetation widths on stream insect community structure can be overcame by other environmental variables, like substrate type, hindering accurate assessments. We tested the effects of different riparian vegetation widths (>40, 30–15, 15–5 and <5 m) along with different substrate types (inorganic and organic) on riffle beetle community structure in southern Brazilian 4th‐ to 5th‐order streams. Riparian buffer widths and substrate types influenced riffle beetle community structure, but no interaction between them was observed. Reduced riparian vegetation widths downstream were associated with changes in riffle beetle dominant genera (Macrelmis predominated only in streams with narrowest riparian widths). Additionally, communities in organic substrates had lower equitability and different dominant genera (Hexacylloepus and Heterelmis) than inorganic ones. Our results showed that reductions in riparian vegetation were associated with water pollution and changes in riffle beetle community structure, suggesting that buffer strips narrower than 5 m are not adequate to maintain environmental integrity of southern Brazilian streams. These results have special importance for the conservation of stream insects in Brazil, as reductions up to less than 5 m in stream banks of small properties are allowed by the new Brazilian Forest Code, independently of stream order.     

Local and regional factors determining aquatic and semi-aquatic bug (Heteroptera) assemblages in rivers and streams of Greece

Heteroptera species were collected from 48 sites distributed throughout the mainland and island complexes of Greece during 1999–2004. The aims of this study were to investigate Heteroptera distribution and abundance in Greek streams, identify the environmental factors that are linked to variation in their assemblages and to partition the influence of environmental and spatial components, alone and in combination, on Heteroptera community composition. Canonical ordination techniques (CCA) were used to determine the relationship between environmental variables and species abundance, while variation partitioning was performed using partial CCA to understand the importance of different explanatory variables in Heteroptera variation. Heteroptera variation was decomposed into independent and joint effects of local (physicochemical variables, microhabitat composition, stream width and depth), regional (land use/cover) and geographic variables (longitude, latitude, altitude and distance to source). Land use/cover, aquatic and riparian vegetation, stream size and water chemistry were the most important factors structuring Heteroptera assemblages. At regional scale, bug assemblages were mainly divided into those found in forested and agricultural landscapes, following water quality and microhabitat composition at local scale. Local variables accounted for 48% of the total explained variation, regional variables for 20% whereas geographical position appeared to be the least influencing factor (8.5%). The results of partial constraint analyses suggested that local variables play a major role in Heteroptera variation followed by regional variables. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Drivers of plant species composition in alder-dominated forests with contrasting connectivity

The effects of local and regional environmental variables as well as spatial gradients on the plant species composition of two types of alder-dominated forests (riparian forests and alder carrs) with contrasting connectivity were studied across the Western Carpathians from Hungary through Slovakia to Poland. We used large vegetation (240 sampling plots) and environmental (24 variables) datasets, which were accompanied by spatial variables represented by principal coordinates of neighbour matrices. Canonical correspondence analysis (CCA) of the two datasets revealed 13 and 29 variables with significant effects on variation in species composition of alder carrs and riparian alder forests, which jointly explained 41.2% and 36.4% of the variability, respectively. Altitude was the most important factor explaining 7.7% of the variability in the species composition of alder carrs and 8.2% in riparian alder forests. Variation partitioning in CCA revealed that local variables were crucial drivers for species composition patterns in alder carrs, while spatial processes unrelated to the measured environmental variables shaped the vegetation structure of riparian forests.

     

嵊州市公益林群落数量分类、排序及环境解析

为探讨群落分布和环境间的内在关系,采用二元指示种分析(TWINSPAN)和典范对应分析(CCA)法对嵊州市公益林植物群落94 块固定监测样地(20 m×20 m)进行数量分类与排序.结果表明,采用TWINSPAN 可将94 个公益林监测样地分成14 组,其中以马尾松为建群种的群丛最多,是该区域主要的优势群落类型.CCA 排序结果较好地反映了植物群落与环境因子的关系,其中坡向和坡位是植物群落分布的主导环境因子.此方法可有效解释植物群落分布格局与环境之间的内在联系,为区域公益林分类经营管理提供科学依据.     

Characterization of diatom assemblages in mid-altitude streams of NW Italy

Following the European Water Framework Directive, this study aims to be the first step to (i) identify diatom type assemblages in unpolluted streams in NW Italy, and (ii) find which ecological factors explain most of the variation. To achieve this, we collected physical, chemical and benthic community data from four streams in NW Italy from 2001 to 2004, for a total of 72 samples. All sampling sites were between 200 m a.s.l. and 800 m a.s.l., but differed in the dominant lithological substrate, i.e. alluvial or siliceous. Relationships between diatom communities and environmental factors were examined using canonical correspondence analysis (CCA), while Indicator Species Analysis was used to define characterizing species and accompanying species of three environmental groups identified by CCA: (1) high water quality and medium saline content, (2) high water quality and low saline content, (3) poor water quality. The diatom assemblages of the three groups of sites differed significantly, as shown by the Multi-Response Permutation Procedure. There were strong correlations between diatoms and environmental factors, especially chlorides (also highly correlated with sulphates and carbonate hardness), nitrate concentration and conductivity. The group 1 assemblage was typical of the alluvial Alpine streams with medium saline content and was characterized by mostly oligosaprobic/β-mesosaprobic taxa such as Cymbella affinis, Diatoma ehrenbergii and Staurosira pinnata. The species assemblage found in the siliceous Alpine rivers with good water quality make them suitable reference sites for a benthic diatom community. Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users Handling editor: K. Martens     

The influence of channelisation on riparian plant assemblages

1. A comparative study of species diversity and assemblage patterns of herbaceous ground‐flora communities in riparian areas was performed along natural mid‐sized lowland streams and their channelised counterparts. The areas had open vegetation and were positioned along 18 similar‐sized third to fourth order stream reaches. 2. Alpha diversity was significantly higher along natural streams both at the sample plot and reach scale. Sample plot diversity peaked at intermediate distance from the natural stream reaches, whereas it increased with increasing distance from the channelised reaches. Both gamma diversity, measured and estimated from species‐area curves, and beta diversity, which is a measure of the change in diversity between areas, was similar along the two types of streams. 3. Alpha diversity correlated with several of the measured and calibrated environmental variables. The positive correlation between bank slope and alpha diversity indicates that flooding plays a key role in maintaining high levels of diversity along natural streams. 4. Species composition varied significantly between the two stream types. A cluster analysis identified four clusters of which two clusters (one and three) primarily included species associated with sample plots in areas along natural streams. Most cluster one and three species were also identified as indicator species for this stream type. 5. Canonical correspondence analysis revealed that cluster one species were less productive species associated with high total soil carbon and nitrogen contents, whereas cluster three species were highly productive species associated with high soil moisture levels, probably partly resulting from flooding. Our results suggest that distance from the stream channel imposes a probabilistic gradient that sustains co‐occurrence of these two communities in riparian areas along natural mid‐sized lowland streams.     

Invertebrate community structure and ecosystem functioning in European conifer plantation streams

1. Terrestrial leaf‐litter is the dominant energy input to many headwater streams and consequently the nature of the riparian vegetation can have profound effects on in‐stream processes. The impact of conifer plantations on community structure and ecosystem functioning (litter breakdown) was investigated in field experiments in three countries (Britain, Ireland, Poland), each representing a distinct European ecoregion. Twenty‐six streams were used in the trial: half were bordered with broadleaved and the other half with conifer riparian vegetation. 2. In a leaf breakdown study using litter bags, two leaf types (oak and alder) were used to assess the impact of resource quality and two mesh sizes (10 and 0.5 mm aperture) were used to gauge the relative importance of invertebrate detritivores and microbial decomposers respectively. Comparisons were made between vegetation types and among regions; pH varied among individual streams but, unlike many previous studies, it was not confounded with vegetation type, enabling us to isolate the effect of vegetation more effectively. 3. Overall, riparian vegetation type did not affect breakdown rates but strong regional differences were observed. There was also a significant interaction between these two variables, but this disappeared after fitting pH as a covariable, demonstrating its importance in determining breakdown rates and raising the possibility that in previous studies the impacts of conifer plantations might have been confounded with pH. 4. Shredder species composition differed between vegetation types. Small stoneflies were most strongly associated with conifer streams; broadleaved streams generally had a higher proportion of larger taxa, such as limnephilid caddisflies and gammarid shrimps, although the latter were excluded from sites with low pH. However, breakdown rates were maintained irrespective of shredder community composition, suggesting a high degree of functional redundancy in these communities. Similar processing rates were observed between streams with high numbers of nemourids and those with only a few limnephilids or gammarids, suggesting that density compensation among consumers might stabilise process rates. 5. Our results suggest that leaf‐litter breakdown can be an effective proxy for assessing stream ecosystem functioning, as rates differed significantly across spatial scales, from between streams to across regions and responded to an environmental gradient (pH). The litter bag technique can also complement traditional assessment methods by providing valuable information on the composition of consumer guilds, thereby providing an important link between structure and function that is needed to help inform management practices.     

Shifts in leaf litter breakdown along a forest–pasture–urban gradient in Andean streams

Tropical montane ecosystems of the Andes are critically threatened by a rapid land‐use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest–pasture–urban) on stream physico‐chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico‐chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land‐use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf‐shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land‐use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of native vegetation and riparian buffers to promote ecological integrity and functioning of tropical Andean stream ecosystems.     

Diversity and microdistribution of black fly (Diptera: Simuliidae) assemblages in the tropical savanna streams of the Brazilian cerrado

We describe the abiotic factors affecting the distribution of black flies at a microhabitat scale, rather than at the regional scale usually present in the literature on the Neotropics. Black fly larvae were sampled from the Tocantins River and three tributaries, located in the Brazilian savanna (state of Tocantins, Brazil) during six bi-monthly sampling periods from October 2004-August 2005. At each sampling site, 15 random quadrats (30 x 30 cm) were sampled each period and for each quadrat were determined mean water velocity, predominant substrate type (rocks, riffle litter or riparian vegetation) and depth detrended correspondence analysis (DCA) was used to determine associations with current velocity, whereas correspondence analysis (CA) was used to estimate site specific current velocity associations. Canonical correspondence analysis (CCA) was used to identify general microhabitat associations. The CCA showed that most species had a trend towards riffle litter, except for Simulium nigrimanum associated with rocky substrate and Simulium cuasiexiguum associated with riparian vegetation. The DCA showed a well defined pattern of water velocity associations. The CA revealed that the species showed different speed associations from one site to another, suggesting different competitive pressures resulting in the occurrence of different realized niches.     

The role of hydro‐environmental factors in Mayfly (Ephemeroptera,Insecta) community structure: Identifying threshold responses

Freshwater organisms are threatened by changes in stream flow and water temperature regimes due to global climate change and anthropogenic activities. Threats include the disappearance of narrow‐tolerance species and loss of favorable thermal conditions for cold‐adapted organisms. Mayflies are an abundant and diverse indicator of river health that performs important functional roles. The relative importance of key hydro‐environmental factors such as water temperature and flow volumes in structuring these communities has rarely been explored in the tropical regions of Africa. Here, we investigate the response of mayfly species diversity to these factors in the Luvuvhu catchment, a strategic water source area in the arid northeastern region of South Africa. Mayfly larvae were sampled monthly in stones‐in‐current biotopes across 23 sites over a one‐year period. The relationship between these environmental drivers and mayfly diversity was modeled using linear mixed effects models (LMMs) and a model‐based multivariate approach. Threshold Indicator Taxa Analysis (TITAN) was used to model the response of mayfly species to important gradients and identify thresholds of change. Site‐specific characteristic were the most important predictor of mayfly diversity, and there was considerable variation over time, with mayfly diversity peaking during winter. Along this, gradient temperature was the best predictor of assemblage structure, with five out of six reliable indicator species being cold‐adapted, and a community threshold response at 19°C. Results support laboratory‐based thresholds of temperature for mayfly species survival and development, extending empirical evidence to include field‐based observations. Increased global (climate change) and local (riparian vegetation removal, impoundments) changes are predicted to have negative impacts on mayfly diversity and ultimately on ecosystem function.     

Diversity of aquatic hyphomycetes in the aquatic ecosystems of the Western Ghats of India

Relationships between physico-chemical factors of waters, riparian vegetation, altitude and species richness of the hyphomycete communities in six rivers and a sulfur spring in the Western Ghats of Karnataka were analysed statistically. Linear regression and correlation between log fungal species and riparian vegetation was highly significant. The similarity in the fungal diversity between different rivers and the sulphur spring was evaluated by Sorensen's index. Generally, the indices of similarity in the mycoflora between the streams were high. However, in the streams of Lakya, Bhadra, Ranganathittu bird sanctuary and the sulfur spring the indices of similarity were low compared with the rest of the water systems. The low pH, low oxygen concentration, hardness, high iron, high temperature and sulfide contents of the waters of these streams are thought to be the reasons for the differences in these streams. Anguillospora longissima, Helicomyces roseus, Lunulospora curvula, Triscelophorus monosporus and Wiesneriomyces laurinus were found to be the most abundant species.     

岷江上游河岸带土地覆盖格局及其生态学解释

针对岷江上游干流河岸带的土地覆盖状况,将该区沿河流主干分为68个样方,结合空间信息及环境因子,对这些样方及流域内的12种土地覆盖类型,采用双向指示种分析法(Two-way indicator species analysis, TWINSPAN)和除趋势典范对应分析法(Detrended canonical correspondence analysis, DCCA)对种类和样方进行分类和排序,以揭示其生态学意义及环境影响因素。结果显示:1)研究区土地覆盖可分为高植被覆盖、中度植被覆盖和低/非植被覆盖3种类别,各类别在流域不同位置分布状况不同,整个流域以中度植被覆盖为主。2)所取样方可分为8个类群,各自拥有相似的土地覆盖组成,呈聚集分布。3)根据土地覆盖特征,河岸带可分为上、中、下3段,流域上段河岸带植被覆盖度较高;中段以中度植被覆盖类型为主,占总面积最大;下段集中了大部分人工土地覆盖类型。4)气温、海拔是影响岷江上游干流河岸带土地覆盖格局的最重要因素,此外降水和人类活动对其也有影响。除干旱河谷区外,顺流自上而下,海拔逐渐降低,水热条件逐渐改善,同时人类干扰强度也逐渐增加,是造成流域3段截然不同的土地覆盖格局的原因。5)干旱河谷特殊的土地覆盖格局是水、热共同作用造成的。总之,岷江上游河岸带土地覆盖呈现出一定的梯度变化特征,自然条件的制约是形成这一格局的主要原因。     

BIOGEOGRAPHY OF BATRACHOSPERMUM HELMENTOSUM (BATRACHOSPERMALES, RHODOPHYTA) IN NORTH AMERICA USING MOLECULAR AND MORPHOLOGICAL DATA

Over the course of 3 years (1997–1999), 72 stream sites were sampled for epilithic diatom communities. The analysis of these samples has led to the identification of over 325 species of diatoms. In addition to sampling the diatom community, selected physical and chemical parameters were recorded from each stream reach. These parameters included pH, specific conductance, current velocity, SRP, nitrate, silica, and total alkalinity. Canonical Correspondence Analysis (CCA) was used to identify influential environmental parameters and to assess the response of the diatom community to prominent anthropogenic inputs in the region (i.e. coal mine drainage, eutrophication). The initial analyses indicate that pH was the most influential environmental parameter along the first CCA axis. This shift was not unexpected, as acid mine drainage (AMD) in the region leads to a wide range of pH values (2.8–7.93). The highly acidic sites were characterized by species of the genus Eunotia (specifically E. exigua and E. steineckei ), Frustulia rhomboides , and Pinnularia subcapitata. Furthermore, Achnanthidium minutissimum was the most widely distributed of the diatom species encountered, being found at 94% of the sites sampled. Streams that fluctuated between acidic and circumneutral pH (termed "teeter-totter") had greater abundances of Brachysira vitrea than other streams in this survey. Further implications for the use of these diatom communities as biomonitoring tools and the distribution of assemblages within the Western Allegheny Plateau will be discussed.     

Role of environmental and spatial processes in structuring anuran communities across a tropical rain forest

This study aimed to evaluate if anuran species distributions in riparian and non‐riparian areas are influenced by environmental factors (i.e. niche) and/or by spatial factors (i.e. dispersal). The environmental variables analysed were altitude, distance from the stream and leaf litter depth. Spatial factors were represented by the eigenvectors extracted from geographical coordinates by eigenfunction analysis. The study was conducted in 24 km² of terra‐firme forest in Central Amazonia, Manaus – Amazonas, Brazil. Between November 2008 and May 2009, three samples were taken from 41 plots, 21 plots being placed at non‐riparian areas and another 20 placed in riparian areas. We submitted the assemblage dataset to a partial redundancy analysis to evaluate the contributions of environmental and spatial variables (selected with a forward selection procedure). In addition, we tested if communities differ from riparian and non‐riparian areas using a db‐MANOVA. Species richness and species composition differed between riparian and non‐riparian plots. Some species were restricted to riparian areas. Altitude was the only significant variable (P = 0.005) explaining 21% of the total variance. When analysing the data from all plots using the partial redundancy analysis, 27% of the variance was explained by spatial and environmental variables. The environmental variables explained exclusively 4% of the variance in assemblage composition, and 13% was explained by environmental variables that were also structured in space (i.e. the shared fraction), while 10% was explained exclusively by spatial variables. In conclusion, our results showed differences between the assemblages of riparian and non‐riparian areas which can be explained by the distribution of anuran species along environmental gradients altitude and distance to streams, with little evidence of dispersal limitation.     

Importance of scale,land‐use,and stream network properties for riparian plant communities along an urban gradient

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