High congruence of intraspecific variability in floral scent and genetic patterns in Gentianella bohemica Skalický (Gentianaceae)

Gentianella bohemica Skalický (Gentianaceae) is a critically endangered species endemic to the Bohemian Massif in the border region of Germany, Czechia and Austria. It consists of a restricted number of extremely scattered populations which are known to form distinct genetic groups. The objective of this work was to test for differences in the floral scent between Gentianella bohemica and Gentianella germanica and within these two species among populations, and to test for a correlation of scent and genetic similarity among the populations of G. bohemica. Floral scent was collected from the inflorescences/plants of eight flowering populations of G. bohemica and three populations of G. germanica using dynamic headspace methods, followed by GC/MS analyses. Both species emitted several aromatic and terpenoid compounds and multivariate analyses revealed differences in scent between the two species and within species among G. bohemica populations. Volatile components overlapped as expected for closely related species but floral scent was taxon-specific. Floral scent differentiation among G. bohemica populations was in high congruence with the genetic differentiation suggesting that scent differences among populations have a genetic basis and showing that scent is a suitable chemotaxonomic marker in this species.     

Phytoplankton assemblage structure and dynamics as indicator [-2pt] of the recent trophic and biological evolution of the western basin of Lake Como (N. Italy)

We studied the phytoplankton assemblage of the western basin of Lake Como (Northern Italy) during 1997. The phytoplankton assemblage was composed of 65 taxa, belonging to six taxonomic groups. Chlorophyta were represented by the highest number of taxa (28) followed by Bacillariophyceae (17), Cyanoprokaryota (9), Dinophyceae (6), Chrysophyceae (3) and Cryptophyta (2). The total assemblage density and biomass ranged from 902 ind ml^–1 and 134.5 mm³ m^–3 in February to 58 766 ind ml^–1 and 9360 mm³ m^–3 in October. The density and biomass variation at three stations showed a common pattern, with higher values in the southern part of the basin where TP concentrations were always greater. The phytoplankton succession was analysed by cluster analysis (average linkage clustering) and non-metric multidimensional scaling (NMDS) ordination, both applied to a dissimilarity matrix obtained from a calculation of the Bray–Curtis index. In general, the seasonal succession followed a simple pattern, with a clear spring phase. These results are discussed considering the trophic evolution of the lake and its recent colonization by Dreissena polymorpha.     

Evaluating Wetland Restoration Success Using Aquatic Macroinvertebrate Assemblages in the Sacramento Valley,California

Currently, there is little professional consensus as to which ecological metrics should be used to measure restoration success in wetlands. Aquatic macroinvertebrate communities have many qualities to recommend them as useful metrics in this manner; yet, they have not been widely used to evaluate wetland restoration success. We examined the macroinvertebrate communities of four restored seasonal wetlands across a chronosequence of postrestoration age and compared them to a remnant natural wetland in the Central Valley of California. We examined two qualitatively different sets of aquatic macroinvertebrate metrics, general measures of community properties (abundance, richness, and diversity) and specific assemblage membership (nonmetric multidimensional scaling and permutational multivariate analysis of variance). Our results using these two different sets of metrics give us different answers. The general measures suggest that wetland macroinvertebrate communities converge on relatively stable values sometime after 10 years postrestoration. The specific assemblage results imply that the particular set of taxa found in restored wetlands is not predictable over the chronosequence we examined. Taken together, our results suggest that aquatic macroinvertebrate communities may be useful for measuring some aspects of restoration success but that there is unlikely to be a final aquatic community pattern indicating restoration success.     

Compositional differentiation,vegetation‐environment relationships and classification of willow‐characterised vegetation in the western Eurasian Arctic

Question: How does willow‐characterised tundra vegetation of western Eurasia vary, and what are the main vegetation types? What are the ecological gradients and climatic regimes underlying vegetation differentiation? Location: The dataset was collected across a wide spectrum of tundra habitats at 12 sites in subarctic and arctic areas spanning from NW Fennoscandia to West Siberia. Methods: The dataset, including 758 vegetation sample plots (relevés), was analysed using a TWINSPAN classification and NMDS ordination that also included analyses of vegetation‐environment correlations. Results: Based on the TWINSPAN classification, eight vegetation types characterised by willow (cover of upright willows >10%) were discerned: (1) Salix glauca‐Carex aquatilis type, (2) Aulacomnium‐Tomentypnum type, (3) Salix‐Betula‐Hylocomium type, (4) Salix lanata‐Brachythecium mildeanum type, (5) Salix‐Pachypleurum type, (6) S. lanata‐Myosotis nemorosa type, (7) Salix‐Trollius‐Geranium type and (8) Salix‐Comarum palustre‐Filipendula ulmaria type. Willow‐characterised vegetation types were compositionally differentiated from other tundra vegetation and were confined to relatively moist valley and sloping tundra sites, from mire to mineral soils. These vegetation types were encountered across a broad latitudinal zone in which July mean temperature ranged from 6 to 10°C. Conclusions: Willow‐characterised tundra vegetation forms a broad category of ecologically and geographically differentiated vegetation types that are linked to dwarf shrub tundra, shrub tundra or mire. Because of complex ecological gradients underlying compositional differentiation, predicting the responses of willow‐characterised tundra vegetation to a warming climate may be complicated.     

Towards a physiological response of fishes under variable environmental conditions: An approach through neural network

Present study aims to explore the effectiveness of environmental factors as predictive markers for assessing their impact on stress and endocrine physiology in selected five ecologically important fish species of Sundarban mangrove estuarine area, India. Our goal was to develop a realistic integrated conceptual model to analyze and envisage the consequence of fluctuating environmental parameters on the stress physiology of these fishes and their adaptive responses to thrive in such environment. Fishes were collected monthly throughout the year from 3 different study sites and various anti-oxidant (enzymatic and non-enzymatic) and detoxification enzymes were measured. Levels of the stress hormone cortisol and reproductive hormone 17β-estradiol were also measured as indicators of stress accumulation and reproductive status of the selected fish species. The study sites showed variations in physical factors such as pH, dissolved oxygen, temperature and salinity, which may be related to environmental fluctuation and/or pollution level. Such panel of multiple enzyme and hormone biomarkers in fish might be a useful tool to develop an assessment model. This study demonstrated a sharp indication of variation in the antioxidant enzyme profiles depending on the physical environment but the changes is exclusively site as well as species specific. To justify our assumptions cluster and non-metric multidimensional scaling (NMDS) analysis have been done to investigate the ordination of physiological parameters and water quality parameters; if it varies for each species or not. Levels of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidise (GPx), malondialdehyde (MDA) and glutathione (GSH) showed variations depending on the physical environment but the changes is exclusively site as well as species specific. Finally, the prediction model and NMDS scaling confirmed MDA, GST and GSH as decisive factor to envisage steroid hormone, whereas organic carbon, temperature, ammonia and alkalinity as the major contributor of its prediction.     

The influence of spatial scale on the genetic structure of a widespread tropical wetland tree, Pterocarpus officinalis (Fabaceae)

Identifying factors that cause genetic differentiation in plant populations and the spatial scale at which genetic structuring can be detected will help to understand plant population dynamics and identify conservation units. In this study, we determined the genetic structure and diversity of Pterocarpus officinalis, a widespread tropical wetland tree, at three spatial scales: (1) drainage basin “watershed” (<10 km), (2) within Puerto Rico (<100 km), and (3) Caribbean-wide (>1000 km) using AFLP. At all three spatial scales, most of the genetic variation occurred within populations, but as the spatial scale increased from the watershed to the Caribbean region, there was an increase in the among population variation (Φ_ST=0.19 to Φ_ST=0.53). At the watershed scale, there was no significant differentiation (P=0.77) among populations in the different watersheds, although there was some evidence that montane and coastal populations differed (P<0.01). At the island scale, there was significant differentiation (P<0.001) among four populations in Puerto Rico. At the regional scale (>1000 km), we found significant differentiation (P<0.001) between island and continental populations in the Caribbean region, which we attributed to factors associated with the colonization history of P. officinalis in the Neotropics. Given that genetic structure can occur from local to regional spatial scales, it is critical that conservation recommendations be based on genetic information collected at the appropriate spatial scale.     

Diatom Assemblages and their Associations with Environmental Variables in Oregon Coast Range Streams, USA

The Oregon Coast Range, rich in natural resources, is under increasing pressure from rapid development. The purpose of this study was to examine diatom species patterns in relation to environmental variables in streams of this region. Diatoms, water quality, physical habitat and watershed characteristics were assessed for 33 randomly selected stream sites. Watershed size, elevation, geology, vegetation and stream morphology varied substantially among sites. Streams were characterized by dilute water chemistry and a low percent of fine substrate. A total of 80 diatom taxa were identified. Taxa richness was low throughout the region (median 15, range 10–26). Assemblages were dominated by two adnate species, Achnanthidium minutissimum and Achnanthes pyrenaicum. Diatoms sensitive to organic pollution dominated the assemblages at all sites (median 85%). Non-metric multidimensional scaling (NMDS) and correlational analysis showed quantitative relationships between diatom assemblages and environmental variables. NMDS axes were significantly correlated with watershed area, watershed geology, conductivity, total nitrogen, total solids and stream width. Diatom-based site classification (Two-way Indicators Species Analysis, (TWINSPAN)) yielded 4 discrete groups that displayed weak correlations with environmental variables. When stream sites were classified by dominant watershed geology, overall diatom assemblages between groups were significantly different (Analysis of Similarity (ANOSIM) global R = 0.19, p < 0.05). Our results suggest that streams in the coastal region are in relatively good condition. High natural variability in stream conditions in the Oregon Coast Range ecoregion may obscure quantitative relationships between environmental variables and diatom assemblages. A bioassessment protocol that classifies sites by major landscape variables and selects streams along the major human disturbance gradient might allow for detection of early signs of human disturbance in environmentally heterogeneous regions, such as the Pacific Northwest.     

Spatial and temporal distributions of epiphytic diatoms growing on Thalassia testudinum Banks ex König: relationships to water quality

The spatial and temporal distributions of the epiphytic diatom flora on Thalassia testudinum was described within the Florida Bay estuary and at one Atlantic site east of the Florida Keys over a 1-year period. Species of the genus Mastogloia dominated the epiphytic diatom flora (82 out of 332 total species). Nonmetric Multidimensional Scaling (NMDS) and Analysis of Similarity (ANOSIM) revealed four distinct spatial assemblages and two temporal assemblages. Eastern and western Florida Bay assemblages were identified within the estuary. The eastern diatom assemblage was characterized by high relative abundances of Brachysira aponina and Nitzschia liebetruthii, while the western assemblage was characterized by the abundance of Reimerothrix floridensis, particularly during summer. Two diverse and distinct marine assemblages, one located in the Gulf of Mexico along the western edge of Florida Bay and the other behind the Florida reef tract in the Atlantic Ocean, were also identified. Analysis of the spatial distribution of diatoms and water quality characteristics within Florida Bay suggest that these assemblages may be structured by salinity and nutrient availability, particularly P. The Gulf of Mexico and the western Florida Bay assemblages were associated with higher water column salinities and TP concentrations and lower DIN concentrations and TN:TP ratios relative to the eastern Florida Bay assemblage. The temporal variation in diatom assemblages was associated with water temperature, though temporal indicator species were few relative to the number of spatial indicators. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.