Alteration of dominant cyanobacteria in different bloom periods caused by abiotic factors and species interactions

Freshwater cyanobacterial blooms have drawn public attention because they threaten the safety of water resources and human health worldwide.Heavy cyanobacterial blooms outbreak in Lake Taihu in summer annually and vanish in other months.To find out the factors impacting the cyanobacterial blooms,the present study measured the physicochemical parameters of water and investigated the composition of microbial community using the 16S rRNA gene and internal transcribed spacer amplicon sequencing in the months with or without bloom.The most interesting finding is that two major cyanobacteria,Planktothrix and Microcystis,dramatically alternated during a cyanobacterial bloom in 2016,which is less mentioned in previous studies.When the temperature of the water began increasing in July,Planktothrix appeared first and showed as a superior competitor for M.aeruginosa in NO3^−-rich conditions.Microcystis became the dominant genus when the water temperature increased further in August.Laboratory experiments confirmed the influence of temperature and the total dissolved nitrogen(TDN)form on the growth of Planktothrix and Microcystis in a co-culture system.Besides,species interactions between cyanobacteria and non-cyanobacterial microorganisms,especially the prokaryotes,also played a key role in the alteration of Planktothrix and Microcystis.The present study exhibited the alteration of two dominant cyanobacteria in the different bloom periods caused by the temperature,TDN forms as well as the species interactions.These results helped the better understanding of cyanobacterial blooms and the factors which contribute to them.

The composition of mixed-species flocks of birds in and around Chitwan National Park,Nepal

Background:Mixed-species flocks(MSFs)have been well sampled in the South Asia,but there has been as yet surprisingly little work on MSFs of Nepal,despite a diverse and well-studied avifauna.We surveyed MSFs in two forest types in and around the Important Bird Area of Chitwan National Park in Nepal,between 150 and 800 m a.s.l.,to provide a first description of the composition of MSFs in this area.We also aimed to understand which species should be considered‘nuclear species',important to forming MSFs or leading them forward.Results:In total,we collected records on 222 MSFs that included 100 species,and 6097 individuals.The MSFs were similar to worldwide patterns in being dominated by leaf-gleaning,non-terrestrial insectivores.However,the MSFs were more dominated by canopy species than usual,and did not have a clear gregarious,understory leading species.Rather drongos(Family Dicruridae)and minivets(Family Campephagidae,Genus Pericrocotus)acted as leaders,and a cluster analysis of composition showed one group of large body size MSFs particularly characterized by the presence of the Greater Racket-tailed Drongo(Dicrurus paradiseus).Conclusions:Drongos are known to provide both costs and benefits to other flock participants:they are aggressive birds that can steal food,and manipulate other species with their vocalizations,but at the same time they are‘sentinel species'that produce information about predation risk other species can use.This study demonstrates that drongos can be considered nuclear species for some types of MSFs,despite the potential costs of their presence.MSFs led by sentinel species thus may form in Asia,as well as in the Neotropics.

Reactive Oxygen Species during Plant-microorganism Early Interactions

Reactive Oxygen Species （ROS） are continuously produced as a result of aerobic metabolism or in response to biotic and abiotic stresses. ROS are not only toxic by-products of aerobic metabolism, but are also signalling molecules involved in several developmental processes in all organisms. Previous studies have clearly shown that an oxidative burst often takes place at the site of attempted invasion during the early stages of most plant-pathogen interac- tions. Moreover, a second ROS production can be observed during certain types of plant-pathogen interactions, which triggers hyper- sensitive cell death （HR）. This second ROS wave seems absent during symbiotic interactions. This difference between these two responses is thought to play an important signalling role leading to the establishment of plant defense. In order to cope with the deleterious effects of ROS, plants are fitted with a large panel of enzymatic and non-enzymatic antioxidant mechanisms. Thus,increasing numbers of publications report the characterisation of ROS producing and scavenging systems from plants and from microorganisms during interactions. In this review, we present the current knowledge on the ROS signals and their role during plant-microorganism interactions.

The Lynx and Hare Data of 200 Years as the Nonlinear Conserving Interaction Based on Noether’s Conservation Laws and Stability

We applied n-variable conserving nonlinear differential equations (n-CNDEs) to the population data of the 10-year cycles of Canadian lynx (1821-2016) and the snowshoe hare (1845-1921). Modeling external effects as perturbations to population dynamics, recovering and restorations from disintegrations (or extinctions), stability and survival strategies are discussed in terms of the conservation law inherent to dynamical interactions among species. The 2-variable conserving nonlinear interaction (2CNIs) is extended to 3, 4, ... n-variable conserving nonlinear interactions (n-CNIs) of species by adjusting minimum unknown parameters. The population cycle of species is a manifestation of conservation laws existing in complicated ecosystems, which is suggested from the CNDE analysis as a standard rhythm of interactions. The ecosystem is a consequence of the long history of nonlinear interactions and evolutions among life-beings and the natural environment, and the population dynamics of an ecosystem are observed as approximate CNIs. Physical analyses of the conserving quantity in nonlinear interactions would help us understand why and how they have developed. The standard rhythm found in nonlinear interactions should be considered as a manifestation of the survival strategy and the survival of the fittest to the balance of biological systems. The CNDEs and nonlinear differential equations with time-dependent coefficients would help find useful physical information on the survival of the fittest and symbiosis in an ecosystem.

Interspecific interactions between burrowing dung beetles and earthworms on yak dung removal and herbage growth in an alpine meadow

Interspecific interactions between two spatiotemporally co-occurred species sharing a single resource are considered to be either competitive or facilitative.This study examined the possible interspecific interactions between a dung-tunneling beetle species(Onthophagus yubarinus)and an earthworm species(Aporrectodea noctuma),two major detritivores responsible for dung removal in a Tibetan alpine meadow.We conducted a two-way,factorial field experiment using replicated chambers,and measured the performances of beetles and earthworms,as well as yak dung removal,soil properties and aboveground plant biomass over two months.Earthworm presence significantly decreased the body size of beetle larvae and the weight of tunnel dung that beetle larvae live on.In contrast,beetle presence did not affect the performance of earthworms.Beetles,earthworms and their interaction significantly increased dung removal and soil organic carbon concentration at the end of the experiment.Beetles alone significantly increased soil total N and P,soluble N and P concentrations,but earthworms alone had nonsignificant effects on these nutrient variables.Beetles and earthworms additively enhanced soluble N and P concentrations,and aboveground plant biomass at the end of the experiment.These results indicate 1)there was a one-sided negative relationship between dung-tunneling beetles and earthworms,resulting from the consumption of earthworms on food resource of beetle larvae;and 2)the coexistence of beetles and earthworms facilitated dung removal interactively and plant growth additively by increasing nutrient availability.

The Growth and Species-by-site Interaction of 18 Central American Multipurpose Tree Species Grown at 15 Tropical Sites World-wide

From a world-wide plant introduction trial series utilising 25 central American species planted at over 100 sites in nearly 60 countries, eighteen species planted at 15 sites in the tropics were chosen for further study of the factors determining site productivity and site by species interactions. The species were Acacia pennatula, Acacia farnesiana, Albizia guachapele, Ateleia herbert-smithii, Caesalpinia coriaria, Caesalpinia eriostachys, Caesalpinia velutina, Enterolobium cyclocarpum, Gliricidia sepi...

Temporal patterns of algae in different urban lakes and their correlations with environmental variables in Xi’an,China

Urban lakes were critical in aquatic ecology environments,but how environmental factors affected the distribution and change characteristics of algal communities in urban lakes of Xi’an city was not clearly.Here,we investigated the algal community structure of six urban lakes in Xi’an and evaluated the effects of water quality parameters on algae.The results indicated that the significant differences on physicochemical parameters existed in different urban lakes.The maximum concentration of total phosphorus in urban lakes was(0.18±0.01)mg/L and there was a phenomenon of phosphorus limitation.In addition,51 genera of algae were identified and Chlorella sp.was the dominant algal species,which was affiliated with Chlorophyta.Network analysis elucidated that each lake had a unique algal community network and the positive correlation was dominant in the interaction between algae species,illustrating that mature microbial communities existed or occupied similar niches.Redundancy analysis illustrated that environmental factors explained 47.35% variance of algal species-water quality correlation collectively,indicating that water quality conditions had a significant influence on the temporal variations of algae.Structural equation model further verified that algal community structure was directly or indirectly regulated by different water quality conditions.Our study shows that temporal patterns of algal communities can reveal the dynamics and interactions of different urban ecosystem types,providing a theoretical basis for assessing eutrophication levels and for water quality management.

Interspecific and intraspecific variation in specific root length drives aboveground biodiversity effects in young experimental forest stands

Aims Although the net biodiversity effect(NE)can be statistically partitioned into complementarity and selection effects(CE and SE),there are different underlying mechanisms that can cause a certain partitioning.Our objective was to assess the role of resource partitioning and species interactions as two important mechanisms that can bring about CEs by interspecific and intraspecific trait variation.Methods We measured tree height of 2493 living individuals in 57 plots and specific root length(SRL)on first-order roots of 368 of these individuals across different species richness levels(1,2,4,8 species)in a large-scale forest biodiversity and ecosystem functioning experiment in subtropical China(BEF-China)established in 2009.We describe the effects of resource partitioning between species by a fixed component of interspecific functional diversity(RaoQ)and further effects of species interactions by variable components of interspecific and intraspecific functional diversity(community weighted trait similarity and trait dissimilarity,CWS and CWD).Finally,we examined the relationships between biodiversity effects on stand-level tree height and functional diversity(RaoQ,CWS and CWD)in SRL using linear regression and assessed the relative importance of these three components of functional diversity in explaining the diversity effects.Important Findings Our results show that species richness significantly affected SRL in five and tree height in ten out of 16 species.A positive NE was generally brought about by a positive CE on stand-level tree height and related to high values of RaoQ and CWS in SRL.A positive CE was related to high values of all three components of root functional diversity(RaoQ,CWS and CWD).Our study suggests that both resource partitioning and species interactions are the underlying mechanisms of biodiversity effects on stand-level tree growth in subtropical forest.

Spatial point-pattern analysis as a powerful tool in identifying pattern-process relationships in plant ecology: an updated review

Background:Ecological processes such as seedling establishment,biotic interactions,and mortality can leave footprints on species spatial structure that can be detectable through spatial point-pattern analysis(SPPA).Being widely used in plant ecology,SPPA is increasingly carried out to describe biotic interactions and interpret patternprocess relationships.However,some aspects are still subjected to a non-negligible debate such as required sample size(in terms of the number of points and plot area),the link between the low number of points and frequently observed random(or independent)patterns,and relating patterns to processes.In this paper,an overview of SPPA is given based on rich and updated literature providing guidance for ecologists(especially beginners)on summary statistics,uni-/bi-/multivariate analysis,unmarked/marked analysis,types of marks,etc.Some ambiguities in SPPA are also discussed.Results:SPPA has a long history in plant ecology and is based on a large set of summary statistics aiming to describe species spatial patterns.Several mechanisms known to be responsible for species spatial patterns are actually investigated in different biomes and for different species.Natural processes,plant environmental conditions,and human intervention are interrelated and are key drivers of plant spatial distribution.In spite of being not recommended,small sample sizes are more common in SPPA.In some areas,periodic forest inventories and permanent plots are scarce although they are key tools for spatial data availability and plant dynamic monitoring.Conclusion:The spatial position of plants is an interesting source of information that helps to make hypotheses about processes responsible for plant spatial structures.Despite the continuous progress of SPPA,some ambiguities require further clarifications.

Psorinum 6× triggers apoptosis signals in human lung cancer cells

OBJECTIVE： To provide in vitro evidence of Psorinum treatment against cancer cells in a controlled study. METHODS： Effects of homeopathic Psorinum 6× on cell viability were initially determined in several cancer cell lines, including A549, Hep G2 and MCF-7, using 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide assay, and an ethanol 6× control. The cell line that exhibited highest inhibition was selected and used in the following experiments. A range of Psorinum 6× doses was used to explore treatment effects on cell cycle arrest, cell death（apoptosis）, generation of reactive oxygen species（ROS） and change in mitochondrial membrane potential（MMP） using fl ow cytometry and fl uorescence microscopy, respectively. Expression of several signal proteins related to apoptosis and cell survival were quantified with Western blotting and confocal microscopy. Further, circular dichroism（CD） spectroscopy was used to determine possible drug-DNA interactions, as well as the induction of conformational changes. RESULTS： Treatment of cancer cell lines with Psorinum showed greater anticancer effects in A549 cells than in others. In A549 cells Psorinum treatment inhibited cell proliferation at 24 h after treatment, and arrested cell cycle at sub-G1 stage. It also induced ROS generation, MMP depolarization, morphological changes and DNA damage, as well as externalization of phosphatidyl serine. Further, increases in p53 expression, Bax expression, cytochrome c release, along with reduction of Bcl-2 level and caspase-3 activation were observed after Psorinum 6× treatment, which eventually drove A549 cells towards the mitochondria-mediated caspase-3-dependent pathway. CD spectroscopy revealed direct interaction of Psorinum with DNA, using calf thymus-DNA as target.CONCLUSION： Psorinum 6× triggered apoptosis in A549 cells via both up- and down-regulations of relevant signal proteins, including p53, caspase-3, Bax and Bcl-2.