Effect of riverbed morphology, stream order and season on the structural and functional attributes of caddisfly assemblages (Insecta: Trichoptera)

We tested the individual and joint effects of stream order, riverbed morphology (i.e. pool-riffle sequence), and season on the structural (i.e. species composition, density and richness) and functional (i.e. percent ratio of shredders, collectors, scrapers, and predators) properties of caddisfly assemblages in a closely natural headwater system (Börzsöny Mts., North Hungary). Each factor, both individually and in interaction had a significant effect on caddisfly assemblages as shown by MANOVA analyses. To clarify the effects of stream order, riverbed morphology and season on caddisflies, assemblage properties were also separately studied by ANOVAs. Percent ratio of shredders and collectors were strongly affected by all factors, whereas other attributes were not always sensitive to stream order, season and riverbed morphology. In contrast, species compositions of the reaches differing in stream order and riverbed morphology were significantly different. Our findings on the contrasting differences in shredder composition between riffles and pools may suggest that not only riparian vegetation, but also instream habitat features could shape the accumulation and retention of particulate organic matter (in streams with pool-riffle heterogeneity)

A New Species of the Genus Caminus (Astroporida: Geodiidae) from Korea

Caminus jejuensis n. sp was collected from depth of 20 m at Geomeunyeo, Seogwipo, Jejudo Island by a SCUBA diving from April 2004 to December 2008. This new species is similar to C. chinensis from China in the composition of spicules except for the spherasters and they differ in spicule size and growth form. This species has longer orthotriaenes and spherules, smaller sterrasters and oxyasters than those of C. chinensis. This species also has many spherasters in choanosome, but C. chinensis lacks. Morever, the new species is a massive shape with wrinkles, whereas C. chinensis is a club shape with smooth surface. Description and figures of the new species are provided

Biotic and abiotic factors affecting the microbiota of Chrysomelidae inhabiting wetland vegetation

A subject of particular interest concerns the understanding of which biotic and/or abiotic factors shape the insect’s microbiota composition and diversity. In this study, we focus our attention on the microbiota associated with leaf beetles (Coleoptera: Chrysomelidae) inhabiting a freshwater wetland in Northern Italy for investigating which factors shape it in this peculiar environment. A DNA metabarcoding approach targeting the 16S rRNA has been used to characterize the bacteria associated with seven leaf beetles species living in different zones of the wetland (trees/shrubs, meadow and emergent vegetation zones). The obtained results suggest that three factors potentially affecting microbiota diversity and composition are species membership in the first place, then living zone in the wetland and sex. Within the studied species, males were found possibly more prone to acquire bacteria from the surrounding environment, while females’ microbiota of most of the species resulted dominated by symbiotic bacteria (reproductive manipulators, e.g. Wolbachia, or other symbionts with functional roles in the species, e.g. Candidatus Macropleicola in Donacia genus). The present study, even if based on a limited sample size, contributed to exploring the factors affecting the composition and diversity of bacteria associated with Chrysomelidae

A Minimal Model for Vorticity and Gradient Banding in Complex Fluids

A general phenomenological reaction-diffusion model for flow-induced phase transitions in complex fluids is presented. The model consists of an equation of motion for a nonconserved composition variable, coupled to a Newtonian stress relations for the reactant and product species. Multivalued reaction terms allow for different homogeneous phases to coexist with each other, resulting in banded composition and shear rate profiles. The one-dimensional equation of motion is evolved from a random initial state to its final steady-state. We find that the system chooses banded states over homogeneous states, depending on the shape of the stress constitutive curve and the magnitude of the diffusion coefficient. Banding in the flow gradient direction under shear rate control is observed for shear-thinning transitions, while banding in the vorticity direction under stress control is observed for shear-thickening transitions.Comment: 11 pages, submitted to Eur Phys J

Laboratory tank studies of a single species of phytoplankton using a remote sensing fluorosensor

Phytoplankton were grown in the laboratory for the purpose of testing a remote fluorosensor. The fluorosensor uses a unique four-wavelength dye laser system to excite phytoplankton bearing chlorophyll and to measure the chlorophyll fluorescence generated by this excitation. Six different species were tested, one at a time, and each was grown two to four times. Fluorescence measured by the fluorosensor provides good quantitative measurement of chlorophyll concentrations for all species tested while the cultures were in log phase growth. Fluorescene cross section ratios obtained in the single species tank tests support the hypothesis that the shape of the fluorescence cross section curve remains constant with the species (differences in fluorescence cross section ratios are a basis for determining composition of phytoplankton according to color group when a multiwavelength source of excitation is used. Linear relationships exist between extracted chlorophyll concentration and fluorescence measured by the remote fluorosensor during the log phase growth of phytoplankton cultures tested

A comparison between different treeline types shows contrasting responses to climate fluctuations

Treeline position is mainly determined by growth season temperature, but the response of treelines to climate warming is not uniform worldwide. We compared treeline structure, dynamics and thermal profile in nearby areas with different treeline type, species composition and bioclimatic conditions. We performed a detailed survey of different treeline types in three areas of Italian Alps and northern Apennines. Every tree individual was recorded along altitudinal transects from the closed forest to the species limit. Treeline structure and dynamics were described through altitudinal limits of tree height, density and age. Data were elaborated by principal components analysis. Temperature regime of the three sites was assessed from homogeneous historical climatic data. Treeline was different in the three areas for species composition, shape and dynamics. Both Alpine sites showed diffuse treeline, but only one showed advancing dynamics. Apennine treeline was abrupt and static, with higher temperature at the tree limit. Our study showed the variable dynamics of treelines within a relatively restricted area and the connection between treeline shape and dynamics. An important role is played by species composition, determined by bioclimatic and historical features. These factors should be taken into account when modelling future treeline dynamics at global scale

Assessing species and stage specific effects of preservation on fish oocytes over different temporal scales

This study assessed the effect of 10% neutral buffered formalin and of three ethanol solutions of different concentration on Mediterranean sardine and European anchovy oocytes over several temporal scales (days, weeks, months). The two species exhibit differences both in the elemental composition and the shape of their oocytes which further allowed an appraisal of oocyte shrinkage dynamics in relation to oocyte shape, developmental stage and composition. We showed that the effect of the preservative on oocyte size is stage specific while different preservation periods of ovarian material might lead to discrepancies among studies

Simulation Studies on Arrival Time Distributions of Cherenkov Photons in Extensive Air Showers

Atmospheric Cherenkov technique is an established methodology to study TeV energy gamma rays. Here we carry out systematic monte carlo simulation studies of the timing information of Cherenkov photons. Extensive studies have already been carried out in this regard. Most of these are carried out at higher energies with the aim of studying the elemental composition of cosmic rays. However not much attention is paid to the species dependent signatures at TeV energies. In this work, functional fits have been carried out to the spherical Cherenkov shower fronts and the radii of curvature have been found to be equal to the height of shower maximum irrespective of the species or the observation level. Functional fits have also been carried out to describe the pulse shapes at various core distances in terms of well known probability density distribution functions (PDF). Two types of PDF's have been tried viz. gamma function and lognormal function. The variation of the pulse shape parameters as a function of primary energy, observation height and incident angles have been studied. The possibility of deriving the pulse shape parameters like the rise & decay times, full width at half maximum from the easily measurable quantities like the mean and RMS variation of photon arrival times offers a very important new technique which can be easily applied in an observation.Comment: 34 pages, 14 figures, accepted for publication in Astroparticle Physic

Per capita interactions and stress tolerance drive stress-induced changes in biodiversity effects on ecosystem functions

Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity-ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity-productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity-productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions

Pests vs. drought as determinants of plant distribution along a tropical rainfall gradient

Journal ArticleUnderstanding the mechanisms that shape the distribution of organisms can help explain patterns of local and regional biodiversity and predict the susceptibility of communities to environmental change. In the species-rich tropics, a gradient in rainfall between wet evergreen and dry seasonal forests correlates with turnover of plant species. The strength of the dry season has previously been shown to correlate with species composition