First insights into the diversity and ecology of non-biting midges (Diptera: Chironomidae) of the unique ancient Skadar Lake basin (Montenegro/Albania)

Surficial sediments of three northern Egyptian lakes (Manzala, Burullus and Edku) show differences in diatom assemblages deposited in different sites of these lakes. A total of 172 species and varieties belonging to 58 genera were identified and counted from 62 samples. Of these, 163 diatom taxa were recorded from Manzala Lake sediments, 147 taxa were found in Burullus Lake sediments, and 117 taxa were identified in Edku Lake sediments. The considerable variation in the composition and distribution of the diatom assemblages among these lakes was mainly related to differences in the water quality, salinity, the concentration of nutrients and climatic changes. The planktonic diatom Cyclotella meneghiniana was dominant in the majority of the samples from Manzala Lake, but dominant in only a few samples from the middle parts of Burullus and Edku lakes. The non-planktonic epiphytic taxa Cocconeis placentula and Epithemia sorex were the subdominant species in the surface sediments, especially in shallow and marginal parts of the lakes. Multivariate statistical techniques (hierarchical ascending clustering and canonical correspondence analysis) were used to identify ecological groups of diatoms and to investigate which environmental variables were important in explaining the variation between these groups. Eight ecological groups containing distinctive diatom assemblages reflect current environmental conditions; especially saltwater intrusion in the north and nutrient-rich freshwater in the south.

Lake Skadar is the largest limnological feature on the Balkan Peninsula, and in Montenegro, it holds the status of a national park and is listed on the Ramsar list as an extremely important wetland area. The aim of the study is to analyze the trend of changes in the water levels of Lake Skadar and determine the possible influence of atmospheric and oceanic oscillations on the hydroclimate of the observed area over the past seven decades. The results obtained have shown a significant trend of decreasing mean monthly water levels of Lake Skadar, consequently affecting its seasonal and annual levels. It has also been determined that in the last 15 years, Lake Skadar has experienced both its highest (2010) and lowest (2017) water levels in the entire instrumental period (since 1948). Therefore, in the long term, the water level is decreasing, while in the short term, the frequency of extreme events is increasing. The reasons for the alarming decrease in the water level of Lake Skadar should be sought in changes in precipitation and temperature in its basin. The research has shown a significant increase in air temperature in the lake's basin, while there are no significant changes in precipitation. There is no doubt that the significant warming has led to increased evaporation of water from the lake and its basin. Furthermore, the results have shown that atmospheric and oceanic oscillations influence the hydroclimate of the observed area (water level, precipitation, and temperature). A statistically significant relationship between the lake's water level, precipitation, and temperature in its basin was found in winter with AO, NAO–slp, NAO–500, MOI–1, MOI–2, WeMO, EAWR, SNAO, and SCAND. Temperature variability in summer and autumn is influenced by AMO, while the influence of EA on this parameter is felt throughout all seasons. No statistical correlation was found with any of the considered parameters with indicators of ENSO phenomenon (NINO3.4 and SOI). Regardless of the possible causes of the variability in Lake Skadar's water levels (climate change or natural cycles), decision-makers need to take measures for sustainable management of its hydrological system.

Commercial eucalypt plantation forest has become a unique ecosystem in the wide-range of the tropical and subtropical regions in China. In this unique ecosystem,the under-story vegetation is identified as an important concern for biodiversity conservation and sustainable management for a long run. In the past decade,efforts have been made to understand the species composition and diversity of the vegetation associated with eucalypt and other fast-growing tree plantations. However,much work is still needed to cumulate the knowledge and to provide an overall coverage of this topic and the relevant issues. In the present study,we investigated the under-story vegetation community of short-rotation eucalypt plantations in Gaoyao,Guangdong to compare species composition and diversity at three different age classes,and to study the relationship of species distribution and diversity with soil factors by using canonical correspondence analysis( CCA) and correlation analysis. The result showed that difference in species number significant to a certain extent was observed among three stand age classes when the number of the sampling plots was equal or more than 9,and a size of 24 sampling plots per age class was sufficient for analyzing the species composition. Totally,there appeared 136 vegetationspecies belonging to 54 families and 107 genera in the stand plots sampled,among which there were 80 tree and shrub species,36 herbs and 20 lianas. Although tree and shrub species were rich in number, two herbaceous species( Dicranopteris dichotoma( Thunb.) Bernh. and Miscanthus sinensis Anderss.) were always dominant in abundance and coverage over the stand plots studied. Species number did not significantly differ among stand age classes,but was consistently lower in stands at 1—2 years old than at other two age classes,attributed to the abrupt change and fast restoration of vegetation during and after the establishment stage of stands,respectively. The diversity measures( Simpson index,Shannon index and richness) of the vegetation species were highest for eucalypt stands at 3—4 years old. The ordination analysis indicated that the under-story vegetation species was closely related to the first two ordinations of CCA,with correlation coefficients of 0. 856 and 0. 943,respectively,and the cumulated variance proportion of 51. 1%. While the first ordination axis was obviously controlled by the organic matter and total phosphorus,the second ordination axis was mainly contributed by the total potassium and soil bulk density. The species distribution pattern was significantly influenced by these soil factors,and also related to the pH value in a way. In contrast,the vegetation species diversity was consistently shaped by the total nitrogen and pH value,increasing with the total nitrogen and pH value from low to neutral level. Fertile forest soils with neutral pH value favored to restore or maintain the vegetation diversity associated with short-rotation and intensively managed plantations. We also discussed the negative effects on under-story vegetation of developing shortrotation plantation in large scale and intensive silvicultural operations such as forest road network building and maintenance,burning,site clearance and preparation,weeding,clear-cut and log transportation,etc. Eucalypt cultivation reduces species diversity through changed forest environments and soil properties such as physical structure,moisture and nutrient.

Summary1. Few extensive lotic studies have examined patterns in the biodiversity of non‐biting midges (Diptera: Chironomidae) along major environmental gradients. Our aim was to fill this gap by describing patterns in species diversity, assemblage composition and distributions of midges across a boreal drainage basin.2. We found that the diversity of midges, as measured by rarefied species richness, Fisher’s α and Pielou’s evenness, responded positively to stream size in regression analysis. By contrast, species density was most strongly correlated to a gradient in suspended solids and phosphorus in stream water, as well as macrophyte cover. Spatial variables were not significantly correlated with species diversity.3. Midge assemblage composition was best explained by a model incorporating five composite environmental gradients in canonical correspondence analysis. The environmental gradients were stream size, macrophyte cover, alkalinity, nitrogen and suspended solids. Spatial variables did not overcome the effects of environmental gradients on assemblage composition.4. Cluster analysis divided the 27 study sites into four groups with relatively similar midge assemblages. These groups were statistically significant in multi‐response permutation procedure, and 15 of the 49 midge taxa recorded varied significantly among the groups in indicator value analysis. Discriminant function analysis showed that stream size, macrophyte cover and habitat structure predicted 66.7% of sites into correct groups.5. The information provided by the present analyses may be of considerable importance in conservation planning at the drainage basin level. The fact that species diversity and assemblage composition varied primarily along the stream size gradient suggests that sites belonging to the different size classes (first to fifth order) are needed to conserve the biodiversity of midges. The other environmental gradients should also be considered in conservation planning, because they explained significant amounts of variability in midge assemblage composition.

AimTo evaluate the relative role of environmental factors and geographical position (latitude and longitude) in determining species distribution and composition of local assemblages of butterflies and birds.LocationCzech Republic, central Europe.MethodsCanonical correspondence analysis that ordinates species and samples (grid cells in distribution atlases) such that interspecific and intersample differences attributable to environmental factors are maximized. The technique allowed us to test the significance of individual factors, including the geographical ones, by controlling the other factors and accounting for spatial autocorrelation.ResultsAltitude and climate (temperature and precipitation) accounted for most variance in the interspecific differences in distribution of both butterflies and birds. The distribution of birds was also strongly affected by the area of water bodies, and less strongly, but still significantly, by the area of meadows and mountain open habitats. Habitat types important for the differences in butterfly distribution were deciduous forests, meadows, swamps and mountain open habitats. Some less common habitat types were important only because of the presence of rare species. Latitude and longitude invariably accounted for a large proportion of total variance, and their effect was highly significant even after controlling for the effect of all other environmental factors.Main conclusionsAlthough environmental factors, especially those related to elevation and climate, represent the main determinants of species distribution and composition of local assemblages, the geographical position is very important on this scale of resolution. Understanding distribution patterns, thus, must include not only an understanding of species ecological requirements, but also an understanding of geographical context, which affects structure and dynamics of species’ geographical ranges.

Summary An important goal of community ecology is the assessment of factors that are likely to influence the spatio‐temporal distribution of species assemblages and diversity. Surprisingly, most statistical methods devoted to this have remained poorly interconnected, as well as poorly connected with the popular metrics of diversity estimation. In the present paper we show that important questions related to determinants of species diversity can be specified through a simple multivariate linear model and explored, in common diversity metrics, using standard methods and routines of variance/covariance decomposition. Thanks to an unusual form of presentation of taxonomic data into a table of species occurrences, which considers the individuals as data units, Shannon and Simpson indices as well as species richness can all be expressed as a (weighted) sum of squares. Subsequent apportionments into explained and residual sum of squares provide direct estimates of the beta‐ and alpha‐diversity components with respect to either categorical habitat types or continuous gradient variables. Appropriate statistics and non‐parametric tests are available to assess the significance of these components. Explicit analytical relationships exist between the linear approximation of the table of species occurrences by sampling sites, and the more classical table of species abundances by sites. Therefore, direct links with methods of ordination in reduced space, such as correspondence analysis and canonical correspondence analysis, provide opportunities for partitions that preserve consistency with usual diversity indices. The sum of squares of the approximated occurrence table provides measures of intersites beta‐diversity, from which measures of dissimilarity with explicit references to diversity indices can be derived. Such measures are amenable to distance‐based apportionments through multivariate variograms and multiscale ordination. What are the relative effects of the biological, environmental and anthropogenic factors and of their potential interactions on species diversity? Are these effects stable across scales, from landscape to region, between regions and across ecosystems? The methodological integration proposed in our analytical framework enables one to address these questions using standard statistical tools, and opens new prospects for quantitative biodiversity studies. This also paves the way towards refined models for predicting species diversity at unsampled locations.

The distribution and composition of molluscan assemblages of seagrass beds in the Ensenada de O Grove (north-western Spain), are described in this paper. The studied bottoms were mostly muddy and colonized predominantly by Zostera marina L., Z. noltei Hornemann, or by both species. Molluscan fauna was dominated by gastropods and bivalves, in terms of both species richness and abundance. A total of 7641 individuals belonging to 68 taxa was identified. The most abundant species were the gastropods Peringia ulvae, Retusa truncatula and Calyptraea chinensis and the bivalves Abra alba, Loripes lucinalis and Kurtiella bidentata. Cluster and multidimensional scaling analyses based on Bray–Curtis similarity coefficient showed two distinct faunal assemblages. Group A comprised intertidal sites colonized either by Z. noltei or by Z. marina and Z. noltei on muddy sand and sandy mud bottoms and subtidal sites exclusively colonized by Z. marina in the outer part of the inlet on muddy sand with the highest values of species richness and diversity. Group B consisted of sites characterized by low values of species diversity and a species composition typical of a ‘reduced Macoma community’. The sorting coefficient and the combination of gravel, sorting coefficient and carbonates content (BIOENV analyses) and the salinity of bottom water and depth (canonical correspondence analyses) were the most important abiotic variables in explaining the structure of the molluscan assemblage.

Abstract. We studied floristic and diversity patterns and their environmental controls in two landscapes of contrasting topography in the Patagonian steppe. The analyses were focused on the effects of water availability gradients and landscape configuration on plant species distribution and coexistence.Floristic variation was investigated using Correspondence Analysis. The relationship between floristic and environmental variation was analyzed using Canonical Correspondence Analysis and correlation tests. We explored diversity patterns by relating spatial distance to floristic dissimilarities. The floristic gradient was determined by shrub and grass species and was related to precipitation in the flat area, and to precipitation, elevation and potential radiation in the mountain area. Site species richness increased with water availability in both areas. Mean site species richness and species turnover in space was higher in the mountain than in the flat area. Landscape species richness and floristic gradients were more concentrated in the mountain than in the flat area. In contrast to shrubs and grasses, forb species distributions were uncoordinated and probably independent of any environmental gradient. Our results suggest (1) that landscape configuration affects species composition and diversity through its direct effect on abiotic environmental heterogeneity, and (2) that the environmental controls of the community composition vary depending on the plant functional type considered.

Situated in the transboundary belt between Montenegro and Albania, Lake Skadar is the largest freshwater reservoir in Southeastern Europe. Because of the wide range of endemic, rare or endangered plant and animal species it supports, Lake Skadar and its extensive adjacent wetlands are internationally recognised as a site of significance and importance (Ramsar site). Within the last 10 to 20 years, Lake Skadar was exposed to intensive pollution. For the assessment of the ecotoxic load of the sediments sampled in Lake Skadar, a triad approach was recently applied. Overall, a complex spectrum of ecotoxic loads was elucidated. The aim of the present study was to use plant-based bioassays for assessing the sediment quality of Lake Skadar in order to facilitate and complement the triad test battery. The newly developed sediment contact test with Myriophyllum aquaticum and the aquatic growth inhibition test with Lemna minor were applied to native sediments and pore water, respectively, allowing the investigation of different toxicity-effects caused by particle-bound pollutants as well as pollutants in the interstitial water. This investigation is the first application of the novel sediment contact test with Myriophyllum aquaticum to lake sediments. Sediment samples were taken from nine selected sites at Lake Skadar and investigated by the sediment contact assay with Myriophyllum aquaticum. The pore water was extracted from these sediment samples to be analysed in the aquatic growth inhibition test with Lemna minor. The results of the sediment contact tests were compared with each other and with those of the aquatic growth inhibition test. Both applied macrophyte biotests revealed distinct changes in the growth behaviour of the two macrophytes subsequent to the exposure to the investigated natural sediments of Lake Skadar. The Myriophyllum sediment contact test revealed significant toxicity in the sediment samples from Radus and Kamenik, whereas the aquatic Lemna test showed inhibition effects for the samples from Sterbeq, Plavnica and Kamice. Data obtained with the newly developed Danio rerio contact test and the Arthrobacter globiformis contact test confirmed the Myriophyllum results. Analyses of the heavy metal content in the sediments revealed low or moderate contamination levels. Correlation analyses between the content of heavy metals in the sediments and growth inhibition of Myriophyllum aquaticum showed a significant correlation between Cr concentrations and growth inhibition. Comparable findings are available for a German river system. In contrast, no significant correlation between inhibition rates and concentration of metals could be observed with Lemna minor. It was shown that the newly developed sediment contact test with Myriophyllum aquaticum is applicable to lake sediments. In both the sediment contact test with Myriophyllum aquaticum on whole sediments and the aquatic growth inhibition test with Lemna minor on pore water, plant growth was influenced by the natural sediments and its components. Therefore, both test systems were found to be suitable for the detection of phytotoxic effects upon exposure to sediments. Myriophyllum aquaticum as test organism of the contact test grows directly in the sediment without an additional water-layer. Thus, it is able to detect toxicity caused by particle-bound phytotoxic substances as well as pore water-related contamination, while the floating Lemna minor can only detect effects emanating from pore water. Significant differences of the results were observed between these two test systems and, accordingly, the two different exposure scenarios. Hence, none of the tests can replace the other one and, as a consequence, both should be included into a test battery for the assessment of sediment toxicity. Both plant assays were shown to be reliable tools for the evaluation of the eco-toxicological risk potentials of pore water and solid-phase sediment. They should become a complement to the standardised test battery generally used for comprehensive hazard assessment.

Diatoms were examined in twelve ponds and four small lakes of the Kathmandu Valley, Nepal, to assess their biodiversity, response to environmental conditions and potential use as bioindicators for water quality. They were investigated from different substrates and relationships with water chemistry and habitat character were assessed. In total 212 diatom species were found with 98 taxa at relative abundances > 1 %. The most species-rich genera were Navicula (42), Gomphonema (39), Achnanthes sensu lato (27), Nitzschia (27) and Fragilaria sensu lato (20). Species diversity was low (mean 0.95 ± 0.17 sd) and most assemblages were dominated by 1-3 taxa. Thirty percent of the taxa found could not be identified using relevant literature. Species richness, diversity and evenness were not related to water chemistry or habitat character, but varied significantly on different substrate types and were higher in the sediment compared to stones and macrophytes. At five of seven sites, where several substrates were collected, the most abundant species occurred on all substrates. Canonical correspondence analysis (CCA) revealed that changes in species composition were most strongly correlated with gradients in water chemistry. Achnanthidium minutissimum was characteristic at sites with higher Ca concentrations, while Eolimna minima, Nitzschia palea, Nitzschia palea cf. var. debilis and Gomphonema parvulum indicated higher concentrations of K, Cl, Na, As, Ni, Fe and Al. E. minima and N. palea were also typical at sites with higher concentration of SO 4 2- , Sr and Al. Assemblage composition was also significantly correlated with habitat character such as aquatic vegetation, substrate composition, bank character and land use.

Lake Skadar is the largest freshwater body on the Balkan Peninsula. It is recognized as a wetland of international importance under the Ramsar Convention and holds the status of a national park in Montenegro. The results presented in this study indicate a significant downward trend in monthly water levels during the period 1948-2021, ranging from -14.9 cm in September to -24.0 cm per decade in May. Water levels show significant variation both seasonally and annually (cm per decade): from -16.8 (autumn) to -21.7 (spring), i.e., -19.3 (year). Standardized deviations suggest that the most pronounced decline began in 1981, a pattern further confirmed by the Rescaled Adjusted Partial Sums. Total precipitation in Lake Skadar's drainage basin has shown little to no change. However, there has been a significant increase in air temperature, and thus increased evaporation. According to ERA5-Land data, the annual total evaporation trend in the lake basin reaches up to 10.0 mm per decade. The substantial increase in evaporation has probably resulted in a significant reduction in runoff (Y) derived from precipitation contributing to stream flow. The trend of the mean annual runoff (Y) from 1 m2 is -45 mm per decade, and the flow of the Morača River, the main tributary of the lake, -2.5% per decade. Notably, over the past 14 years, Lake Skadar recorded both its highest water level (2010) and its lowest (2017). We appreciate that the long-term trend of falling water levels is influenced by significant warming of the atmosphere, which has led to increased water evaporation. Short-term fluctuations in lake water levels are primarily driven by variations in precipitation within the catchment area, which are likely linked to atmospheric oscillation patterns. In addition, human impact is evident near the confluence of the Morača River and Lake Skadar, particularly due to the intensive extraction of gravel and sand. To preserve the ecology and economy of Lake Skadar, its natural and cultural heritage, urgent measures are necessary by the countries (Montenegro and Albania) within whose territories this natural gem is located.

In 1949-1951, ecologist Robert H. Whittaker sampled plant community composition at 470 sites in the Siskiyou Mountains (Oregon and California; also known as Klamath or Klamath-Siskiyou Mountains). His primary goal was to develop methods to quantify plant community variation across environmental gradients, following on his seminal work challenging communities as discrete entities. He selected the Siskiyous because of their diverse and endemic-rich flora, which he attributed to geological complexity and an ancient stable climate. He chose sites to span gradients of topography, elevation, geologic substrate, and distance from the coast. He used the frequencies of indicator species in his data to assign sampling locations to positions on the topographic gradient, nested within the elevational and substrate gradients. He originated in this study the concept of diversity partitioning, in which gamma diversity (species richness of a community) equals alpha diversity (species richness in homogeneous sites) times beta diversity (species turnover among sites along gradients). Diversity partitioning subsequently became highly influential and new developments on it continue. Whittaker published his Siskiyou work covering paleohistory, biogeography, floristics, vegetation, gradient analysis, and diversity partitioning in Ecological Monographs in 1960. Discussed in 2 pages of his 60-page monograph, diversity partitioning accounts for >95% of its current >4300 citations. In 2006, we retrieved Whittaker's Siskiyou data in hard copy from the Cornell University archives and entered them in a database. We used these data for multiple published analyses, including some based on (re)sampling the approximate locations of a subset of his sites. Because of the continued interest in diversity partitioning and in historic data sets, here we present his data, including 359 sampling locations and their descriptors and, for each sample, a list of species with their estimated percent cover (herbs and shrubs) and numbers by diameter at breast height (DBH) category (trees). Site descriptors include the approximate location (road, trail, or stream), elevation, topographic aspect, geologic substrate (serpentine, gabbro, or diorite), and dominant woody vegetation of each location. For 111 sites, including the small number chosen to represent the distance-to-coast gradient, we could not locate his data. There are no copyright restrictions and users of these data should cite this data paper in any publications that result from its use. The authors are available for consultations about and collaborations involving the data.

Species composition and longitudinal patterns of fish assemblages in the middle and lower Yarlung Zangbo River, Tibetan Plateau, China

Ten temporary ponds in Northern Pantanal were studied in July 2006 to explore whether a spatial distribution pattern existed in the composition of fish assemblages, and to identify which environmental variables determined their distribution. The existence of any spatial pattern was tested using the multivariate Mantel correlogram, while the influence of environmental variables was quantified by a Canonical Correspondence Analysis (CCA). A total of 8735 individuals was sampled from 29 species, predominantly represented by Hyphessobrycon elachys and Serrapinnus calliurus. Composition of fish assemblages varied among ponds, but this variation had no significant spatial pattern for any of the distance classes considered, thus indicating that the species composition varied independently of the distance between ponds. This suggests that stochastic dispersal processes did not influence the spatial structure of species, as predicted by the neutral theory. Conversely, species composition in the ponds was determined by variables that included depth, macrophyte richness and cover. Species such as Markiana nigripinnis, Crenicichla vittata and Moenkhausia sanctaefilomenae occurred in deeper waters, while Parauchenipterus striatulus, Eigenmannia trilineata and Psellogrammus kennedyi were mainly associated with greater richness and macrophyte cover, as already demonstrated by the niche theory applied in ponds which tended to have similar characteristics and a similar fish composition.

The distribution pattern of epilithic diatoms in the Gui River basin in relation to water quality,land use and topography was investigated by principal component analysis(PCA),corresponding analysis(CA),canonical correspondence analysis(CCA) and partial CCA.Twenty-four sites were sampled throughout the basin,ranging from the mainstream to first order streams.The data indicated that electrical conductivity(EC) increased from upstream to downstream,while other water quality parameters varied across wide ranges.A total of 112 diatom taxa were found in the basin,but only 37 taxa or more were observed in more than 5% of the samples.The most abundant species were Achnanthidium minutissimum,A.pusilla,A.tropica and Cymbella laevis,in order of abundance.Three different groups of taxa were identified,located in the headwater,middle and lowland zones of basin.Nitzschia recta was the dominant species in the lowland zone,A.lanceolata,Amphora montan,and Planothidium frequentissimum were more abundant in the middle zone,while high species diversity was typical of the headwaters.Biological Diatom Index(IBD) and specific PolluoSensitivity Index(IPS) were significantly related to many parameters including Chl.a,NH4-N,altitude,sub-basin catchment area and land use.The first two Principal component analysis axes explained 56.20% of the water quality variance,with the first axis significantly related to NH4-N,NO3-N and TN,and the second axis significantly related to water temperature,pH,EC and dissolved oxygen(DO).The first two Canonical correspondence analysis(CCA) axes collectively explained 28.60% of the species-environment variation.The first CCA axis was significantly positively related to water quality(EC,temperature,NH4-N,NO3-N,and TN),significantly negatively related to land use(areas of urban,agriculture and forest),and significantly positively related to topography(basin areas,altitude and slope).The second two CCA axes were significantly positively related to turbidity.Partial CCA analyses showed that water quality explained a high proportion(48.50%) of the variance,while land use and topographic factors explained 7.20% and 17.50% of the variance respectively.The results indicated that the distribution of diatom assemblages in the Gui River basin was strongly related to water quality parameters,as expected,but was also sensitive to land use and topography.