Do Epiphytes in Drier Climates Select Host Tree Substrates between Rough and Smooth Bole Textures and Crown and Stem, Vertical and Upright Stems? What Are the Implications for Water Catchment and Forest Management?

Epiphyte biomass (dry weight kg) placement between rough and smooth bole bark textures;crown and trunk as well as upright and horizontal substrates in Lusenga National Park were examined through ground surveys. Transects were located at random in woody vegetation using quadrats 20 m × 20 m which were located every 100 m along 1 km long transects. For every host tree substrate sampled, tree species was identified and bark texture was determined. Presence and location of epiphytes were determined through direct observation. Epiphytes were collected, dried and weighed, so as to apportion biomass between rough and smooth bole textures, crown and trunk as well as stem inclination. Rough bole textured stems had more epiphytes of 1967 kg (89%) than smooth bole substrates of 313.48 kg (11%) and also inclined stems had higher biomass of 85% than vertical stems of 14.64% (χ2 = P < 0.005). Trunk had less biomass of 32% and crown had higher biomass of 68% (Mann Whitney U test 0.002 < P < 0.05). It was concluded that epiphytes were more abundant on rough bole textured substrates and in crown than stem. It would appear that rough bole textured substrates provided better physical anchorage and stability against dislodging forces of wind and rain water, hence being suitable for epiphyte establishment and survival. Inclined substrates on the other hand provided a suitable habitat for accumulation of debris and moisture retention, seed settling, germination, and maximum exposure to sunlight all of which support germination and growth of epiphytes. Further research is required to determine successional colonization, incidences of host species specificity, rain water interception and retention and impact of fire on epiphyte biomass as these are important water catchment attributes.

High-quality Cymbidium mannii genome and multifaceted regulation of crassulacean acid metabolism in epiphytes

Epiphytes with crassulacean acid metabolism(CAM)photosynthesis are widespread among vascular plants,and repeated evolution of CAM photosynthesis is a key innovation for micro-ecosystem adaptation.However,we lack a complete understanding of the molecular regulation of CAM photosynthesis in epiphytes.Here,we report a high-quality chromosome-level genome assembly of a CAM epiphyte,Cymbidium mannii(Orchidaceae).The 2.88-Gb orchid genome with a contig N50 of 22.7 Mb and 27192 annotated genes was organized into 20 pseudochromosomes,82.8%of which consisted of repetitive elements.Recent expansions of long terminal repeat retrotransposon families have made a major contribution to the evolution of genome size in Cymbidium orchids.We reveal a holistic scenario of molecular regulation of metabolic physiology using high-resolution transcriptomics,proteomics,and metabolomics data collected across a CAM diel cycle.Patterns of rhythmically oscillating metabolites,especially CAM-related products,reveal circadian rhythmicity in metabolite accumulation in epiphytes.Genomewide analysis of transcript and protein level regulation revealed phase shifts during the multifaceted regulation of circadian metabolism.Notably,we observed diurnal expression of several core CAM genes(especially bCA and PPC)that may be involved in temporal fixation of carbon sources.Our study provides a valuable resource for investigating post-transcription and translation scenarios in C.mannii,an Orchidaceae model for understanding the evolution of innovative traits in epiphytes.

Host plant traits play a crucial role in shaping the composition of epiphytic microbiota in the arid desert,Northwest China

Phyllosphere microorganisms are a crucial component of environmental microorganisms,highly influenced by host characteristics,and play a significant role in plant health and productivity.Nonetheless,the impact of host characteristics on shaping phyllosphere microbial communities of plants with different life forms remains ambiguous.Utilizing high-throughput sequencing technology,this study analyzed the diversity and community composition of phyllosphere epiphytic microorganisms(e.g.,bacteria and fungi)of various plant life forms in the hinterland of the Gurbantunggut Desert,Northwest China.Functional annotation of prokaryotic taxa(FAPROTAX)and fungi function guild(FUNGuild)were employed to assess the ecological functions of microorganisms and to investigate the role of stochastic and deterministic processes in shaping phyllosphere microbial communities.Result showed a diverse array of phyllosphere epiphytic microorganisms in the desert plants,with Proteobacteria,Cyanobacteria,and Actinobacteriota dominating bacterial community,while Ascomycota and Basidiomycota were prevalent in fungal community.Comparison across different plant life forms highlighted distinct microbial communities,indicating strong filtering effects by plant characteristics.FAPROTAX prediction identified intracellular parasites(accounting for 27.44%of bacterial community abundance),chemoheterotrophy(10.12%),and phototrophy(17.41%)as the main functions of epiphytic bacteria on leaves of different life form plants.FUNGuild prediction indicated that phyllosphere epiphytic fungi primarily served as Saprotrophs(81.77%),Pathotrophs(17.41%),and Symbiotrophs(0.82%).Co-occurrence network analysis demonstrated a predominance of positive correlations among different microbial taxa.Raup-Crick dissimilarity index analysis revealed that deterministic processes predominantly influenced phyllosphere bacterial and fungal community assembly.Variance partitioning analysis and random forest modeling suggested that plant leaf functional traits significantly impacted both bacterial and fungal community composition,with fungal community composition showing a closer association with leaf nutrients and physiology compared with bacterial community composition.The distinct responses of bacterial and fungal communities to plant traits were attributed to the differing properties of bacteria and fungi,such as bacteria having higher potential dispersal rates and broader ecological niches than fungi.Overall,the results indicate that phyllosphere bacterial and fungal communities undergo similar community assembly processes,with fungi being more influenced by plant characteristics than bacteria.These findings offer novel insights into the ecology of phyllosphere microbial communities of desert plants.

Elements of disturbance that affect epiphyte vitality in a temperate rainforest:an experimental approach

Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when they fall from the canopy,which limits our understanding of their role in forest carbon sequestration and nutri-ent cycling.In the temperate rainforest of the Quinault River Valley,Washington State,our aim was to test hypotheses regarding four elements of disturbance that might contribute to their decline.Methods We established set of experiments in which we placed samples of canopy epiphytes and their branch segments:(i)in the canopy versus forest floor microenvironment(stratum);(ii)attached to live versus dead branch substrates;(iii)subjected to physical disruption and‘jarring’;and(iv)in direct versus indirect con-tact with the forest floor.Over the 2-year study,we assigned a non-destructive‘vitality index’(based on color and appar-ent mortality and dryness)to each sample every 2-3 months to compare effects of the experimental treatments and analyzed with a statistical model and post hoc pairwise comparisons of treatments.Important Findings The canopy versus ground stratum and live/dead branch status sig-nificantly affected epiphyte vitality.Effects of physical disruption and ground contact were not significant.There were seasonal effects(low vitality during the sampling times in the summer,revitalization upon sampling times in the winter)for all treatments except samples in contact with the ground.One implication of these results relates to effects of climate change,which is predicted to shift to hotter,drier summers and wetter winters.Climate change may affect forest dynamics and nutrient cycling in unpredictable ways.Results also point to future experiments to understand biotic and abiotic effects on epiphyte disturbance and dynamics.

Diversity of culturable alginate lyase-excreting bacteria associated with Sargassum

Large numbers of bacteria live on the surface of various brown algae and can produce alginate lyases to consume alginate,an important component of the cell wall of brown algae.Sargassum is a genus of the largest canopyforming brown algae of more than 150 species,which are widely distributed in tropical and subtropical environments.However,our knowledge about the epiphytic bacteria and the alginate lyase-excreting bacteria from Sargassum is still primitive.Here,we investigated the diversity of the culturable epiphytic bacteria and alginate-degrading bacteria from Sargassum samples collected from the coastal seawaters of Shandong Province,China.In total,37 strains belonging to 21 genera in 3 phyla were isolated,including 15 previously unreported genera,of which Vibrio(6/37)and Pseudoalteromonas(5/37)are the dominant genera.Eight strains,mainly Vibrio and Pseudoalteromonas species,were further identified as alginate lyase-excreting strains that can utilize alginate for growth.The extracellular alginolytic activity of the 8 strains was determined,and strains Vibrio sp.C42and Pseudoalteromonas sp.M9 showed the highest activity.These results provide a better understanding of brown algae epiphytes and alginate-degrading bacteria,and are fundamental for further studies on the interactions between brown algae and their epiphytes.

Temporal characteristics of algae-denitrifying bacteria co-occurrence patterns and denitrifier assembly in epiphytic biofilms on submerged macrophytes in Caohai Lake,SW China

Denitrifying bacteria in epiphytic biofilms play a crucial role in nitrogen cycle in aquatic habitats.However,little is known about the connection between algae and denitrifying bacteria and their assembly processes in epiphytic biofilms.Epiphytic biofilms were collected from submerged macrophytes(Patamogeton lucens and Najas marina L.)in the Caohai Lake,Guizhou,SW China,from July to November 2020 to:(1)investigate the impact of abiotic and biotic variables on denitrifying bacterial communities;(2)investigate the temporal variation of the algae-denitrifying bacteria co-occurrence networks;and(3)determine the contribution of deterministic and stochastic processes to the formation of denitrifying bacterial communities.Abiotic and biotic factors influenced the variation in the denitrifying bacterial community,as shown in the Mantel test.The co-occurrence network analysis unveiled intricate interactions among algae to denitrifying bacteria.Denitrifying bacterial community co-occurrence network complexity(larger average degrees representing stronger network complexity)increased continuously from July to September and decreased in October before increasing in November.The co-occurrence network complexity of the algae and nirS-encoding denitrifying bacteria tended to increase from July to November.The co-occurrence network complexity of the algal and denitrifying bacterial communities was modified by ammonia nitrogen(NH_(4)^(+)-N)and total phosphorus(TP),pH,and water temperature(WT),according to the ordinary least-squares(OLS)model.The modified stochasticity ratio(MST)results reveal that deterministic selection dominated the assembly of denitrifying bacterial communities.The influence of environmental variables to denitrifying bacterial communities,as well as characteristics of algal-bacterial co-occurrence networks and the assembly process of denitrifying bacterial communities,were discovered in epiphytic biofilms in this study.The findings could aid in the appropriate understanding and use of epiphytic biofilms denitrification function,as well as the enhancement of water quality.

Comparison in structure and predicted function of epiphytic bacteria on Neopyropia yezoensis and Neopyropia katadae

The economic alga Neopyropia,which holds significant value in China for its edibility and economic potential,harbors diverse epiphytic bacteria on its surface.The epiphytic bacteria on Neopyropia yezoensis and Neopyropia katadae,two nori species of Neopyropia living at the same tidal level but with distinct physiological states and living habits,were investigated to understand the differences between them and the effects of epiphytic bacteria on their differential characteristics.Analysis of 16S rRNA gene sequences and real-time quantitative PCR(qPCR)of thalli and seawater samples(n=24)revealed notable differences in microbial diversity and community structure between the two species.Bacteroidetes dominated the bacterial communities in association with N.yezoensis,whereas Proteobacteria were predominant in N.katadae.Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt2)analysis revealed enriched genes that related to the ABC transport system,iron complex outer membrane receptor proteins,and proliferation in N.yezoensis,whereas N.katadae exhibited enrichment of genes that related to energy supply as well as cell wall and cell membrane production.The results of qPCR indicate a higher abundance of epiphytic bacteria on surface of N.yezoensis than those on surface of N.katadae.The findings indicate that differences in the living environments of N.yezoensis and N.katadae may result in distinct structural composition and abundance of epiphytic bacteria on their surfaces,thereby conferring specific biological functionalities to each microbial community,and the epiphytic bacteria may shape the living habits of hosts to some extents.This study provided a basis for understanding the close association between surface microorganisms and algal bodies,and the physiological and ecological characteristics of nori species.

Diversity, composition and host-species relationships of epiphytic orchids and ferns in two forests in Nepal

Epiphytic plant species are an important part of biological diversity. It is therefore essential to understand the distribution pattern and the factors influencing such patterns. The present study is aimed at observing the patterns of species richness, abundances and species composition of epiphytic orchids and ferns in two subtropical forests in Nepal. We also studied the relationship of host plants(Schima wallichii and Quercus lanata) and epiphyte species. Data were collected in Naudhara community forest(CF) and the national forest(NF) in Shivapuri Nagarjun National Park. The data were analyzed using univariate and multivariate tests. In total, we recorded 41 species of epiphytes(33 orchid and 8 fern species). Orchid species abundance is significantlyhigher in CF compared to NF. Orchid species richness and abundance increased with increasing southern aspect whereas it decreased with increasing canopy cover, and fern species richness increased with host bark roughness. Orchid abundance was positively correlated with increasing bark p H, stem size, tree age and tree height and negatively correlated with increasing steepness of the area. Likewise, fern abundances were high in places with high canopy cover, trees that were tall and big, but decreased with increasing altitude and southern aspect. The composition of the orchid and fern species was affected by altitude, aspect, canopy cover, DBH, number of forks and forest management types. We showed that the diversity of orchid and fern epiphytes is influenced by host characteristics as well as host types. The most important pre-requisite for a high epiphyte biodiversity is the presence of oldrespectively tall trees, independent of the recent protection status. This means:(i) for protection, e.g.in the frame of the national park declaration, such areas should be used which host such old tall trees;and(ii) also in managed forests and even in intensively used landscapes epiphytes can be protected by letting a certain number of trees be and by giving them space to grow old and tall.

The vertical structure of the vegetative canopy of the brown algae Cystoseira(Black Sea)

In the coastal ecosystems of the Black Sea,macrophytobenthos and,in particular,the association of Cystoseira crinite,C.barbara,Cladostephus verticillatus,and Corallina mediterranea,with its thick vegetative canopy(VC),is the key contributor to primary production(PP).Though the vertical structure of the canopy,formed by the algal association,is of principal importance to the PP level,this subject has been long-neglected by researchers.The goal of our work was to compare vertical structures of the vegetative canopy of Cystoseira brown algae under diverse hydrodynamical conditions of the Crimean Peninsula coast.Samples were collected using the 50 cm×50 cm counting frame at eight stations positioned in shallow(55-60 cm deep)sites of Sevastopol Bay(Crimean Peninsula).Dry weight biomass of the VC was determined for all algae assemblage and for each algal species individually,per horizontal surface unit,at each height(Z).The study shows that:1)the VC is characterized by unimodal vertical distribution of biomass,with maximum estimate in the lower part,where the biomass increases to 85%of the total biomass;2)a series of single-peaked curves reliably describes the unimodal distribution of the biomass;thalli of different age groups are found along the canopy profile;and 3)algae found in epiphytic synusia prefer inhabiting the upper part of the VC.The role of environmental factors(seawater turbulence and solar radiation)is discussed in reference to the formation of the vertical structure,made up of the associations of the brown algae Cystoseira.

Using a Macroalgal Functional Form Approach to Assess the Level of Disturbance of Seagrass Meadows in Bahía of Nuevitas,Cuba(2000-2002)

A study on the spatial and seasonal variations of the associate macroalgae and epiphytes of Thalassia testudinum was carried out in Bahía de Nuevitas. Sixty-two species were identified: 3 Cyanophyta, 25 Chlorophyta, 8 Phaeophyceae, 23 Rhodophyta and 3 Magnoliophyta, with two new records for Cuba and 43 for the area. The differences in the specific composition of the macroalgae communities are determined by a space component related to the type of affectation in each area. The morpho-functional groups of macroalgae in the station with more nutrient influence were mainly foliaceous and filamentous. In the stations far from the city, the predominant morpho-types were the leathery and articulate calcareous indicators of lower nitrification levels. The abundance and diversity of macroalgae in the site affected by fisheries were lower due to the damage by bottom trawls. Seasonal variations were found in the relative abundance of the species, not in the diversity, which makes evident seasonal changes in the structure of the seaweeds, where some species replace others in the community.

Periodic exposure to ambient solar irradiance benefits the growth of juvenile seedlings of Hizikia fusiformis

In our trials, from 2007 to 2008, of mass production of seedlings of Hizikiafusiformis using synchronization techniques, problems of a ＂dark thalli＂ phenomenon and epiphytes contamination severely threatened the health of juvenile seedlings. In this investigation, we optimized conditions for improving the growth of juvenile seedlings. Seven string collectors were seeded with zygotes and a series of experiments were conducted including direct exposure to solar irradiance, co-culture with Ulva spp. and treatment with sodium hypochlorite. It was found that direct exposure to solar irradiance （maximum： 1 740 μmol photons/（m2.s）） for 2 h per day could efficiently enhance the growth of young seedlings and simultaneously inhibit the growth of epiphytic algae. In this treatment, 50-day old seedlings could reach an average of 0.44 cm in length and possess up to nine leaflets. However, a single treatment with 18-mmol/L sodium hypochlorite for 10 rain severely harmed 15-day old seedlings. In comparison, weekly treatment with 2.2-mmol/L sodium hypochlorite for 10 rain brought no apparent harm to seedlings and eliminated epiphytic algae efficiently. However, this treatment significantly increased the detachment rate of seedlings, Inoculating Ulva spp. onto the collector caused a dramatic decrease in the number of seedlings. However, the growth of the remaining seedlings appeared unhampered. All collectors except the control were daily sprayed with a high pressure water jet from the 84 day post fertilization. From the first day to 50th day, no ＂dark thallus＂ was observed on any of the seven collectors. We believe that well-timed daily exposure to solar irradiance would favor H. fusiformis in its early growing stages.

Phylogenetic endemism of the orchids of Megamexico reveals complementary areas for conservation

Orchid diversity provides a unique opportunity to further our understanding of biotic and abiotic factors linked to patterns of richness,endemism,and phylogenetic endemism in many regions.However,orchid diversity is consistently threatened by illegal trade and habitat transformation.Here,we identified areas critical for orchid conservation in the biogeographic province of Megamexico.For this purpose,we evaluated orchid endemism,phylogenetic diversity,and phylogenetic endemism within Megamexico and characterized orchid life forms.Our results indicate that the majority of the regions with the highest estimates of endemism and phylogenetic endemism are in southern Mexico and northern Central America,mostly located on the Pacific side of Megamexico.Among the most important orchid lineages,several belong to epiphytic lineages such as Pleurothallidinae,Laeliinae and Oncidiinae.We also found that species from diverse and distantly related lineages converge in montane forests where suitable substrates for epiphytes abound.Furthermore,the southernmost areas of phylogenetic diversity and endemism of Megamexico are in unprotected areas.Thus,we conclude that the most critical areas for orchid conservation in Megamexico are located in southern Mexico and northern Central America.We recommend that these areas should be given priority by the Mexican system of natural protected areas as complementary conservation areas.

Taxonomy and Ecology of the Lichens of the Ohaliksai River Basin

The article presents information about the taxonomy and ecology of lichens in the Ohaliksai River basin. According to the conducted studies, 11 families of the Lecanoromycetes class (Parmeliaceae, Lecanoraceae, Ramalinaceae, Megasporaceae, Physciaceae, Teloschistaceae, Peltigeraceae, Collemataceae, Candelariaceae, Umbilicariaceae, Physciaceae), 1 family of the Eurotiomycetes class (Verrucariaceae) and 1 family Lichinaceae of the class Lichinomycetes were identified, 18 groups and 23 species were noted as widespread. The taxonomic analysis and ecological characteristics of the identified species are presented.

Floristic Composition and Community Structure of Epiphytic Angiosperms in an Urban Forest Fragment in the Eastern Amazon

Vascular epiphytes are one of the most important forest components,contributing to microclimatic maintenance.These plants find ideal conditions for development in the Amazon due to the spatial heterogeneity and high temperature and humidity typical of this biome.In recent years,the Brazilian Amazon has undergone dramatic changes in its landscape,mainly due to the increase in deforestation and fire rates.We present here the floristic composition and analyze the community structure of epiphytic angiosperms of an urban forest fragment in Eastern Amazon.A total of 71 epiphytic individuals were recorded belonging to eight species and four families.Orchidaceae was the most representative family,corroborating the pattern for surveys of epiphytic diversity in the Neotropical region.Epiphytic species were found on 24 individuals of 10 tree species.The epiphytic importance value(IVe)was low for all species,except for Aechmea tocantina and Rhipsalis baccifera.Cactaceae was the family with the highest IVe.Most epiphytes were found in the crown of trees(83.1%).The diversity index of the fragment was H’=1.80 and the equity index was J=0.87,reflecting the absence of highly dominant species.Conservation of urban forest fragments is necessary for the maintenance of epiphytic flora and ecosystem services.

Occurrence of manglicolous lichens in Calabarzon,Philippines

Various species of mangrove trees thrive in the mangrove forests of Calabarzon,Philippines including species of Avicennia marina,Rhizophora mucronata,and Rhizophora apiculata,which house various lichen species but very little available information on the diversity of these epiphytes is known.A survey of 90 decaying mangrove woods from 3 mangrove sites in Calabarzon including Laiya Batangas,Tanza Cavite and Pagbilao Quezon recorded a total of 40 lichen species classified under 25 genera and 14 families.Rhizophora apiculata(bakawang lalaki)was found the most preferred lichen establishment host as it housed 23 lichen species followed by Rhizophora mucronata(bakawang babae)with 17 lichen species and Avicenia marina with 7 lichen species.Lichens that belong to family Arthoniaceae,Caliciaceae,Parmeliaceae,Collemataceae,and Graphidaceae were the highest recorded.Most of these manglicolous lichens were classified as crustose(60%)and foliose(40%)lichens.Out of these manglicolous lichens identified,29 species were found to be new records of lichens in the Philippines.

Elaphoglossum(Dryopteridaceae-Fern)of Amazon Rainforest in Brazil:Anatomic Characterization and Adaptative Strategies

This study describes the anatomy of sterile leaves of Elaphoglossum discolor (Kuhn) C. Chr., E. flaccidum (Fée) T. Moore and E. laminarioides (Bory ex Fée) T. Moore, the most representative species of the genus in the Ecological Park of Gunma in Pará State. It reports the main diagnostic characters and provides new systematic data for the group. In addition, it locates the production and accumulation sites of bioactive compounds to determine possible adaptive strategies of these species in the Amazon rainforest environment. Diagnostic structural features include stoma typology, central veins and margin forms, type of mesophyll, and the presence of schlerenchymatous sheaths in the cortex, among others. Among the bioactive compounds related to defense adaptation are phenolic compounds, which occur in all three species, and alkaloids and mucilage, which are exclusive to E. laminarioides. Of the three species studied, E. laminarioides has features that make it the best suited to the rainforest environment.

Epiphytic bacterial communities on two common submerged macrophytes in Taihu Lake: diversity and host-specificity

Leaves of terrestrial and aquatic plants are home to a wide diversity of bacterial species. However, the diversity and variability of epiphytic bacteria on their submerged plant hosts remains poorly understood. We investigated the diversity and composition of epiphytic bacteria from two common submerged macrophytes: Vallisneria natans and Hydrilla verticillata in Taihu Lake, Jiangsu, China, using methods of terminal restriction fragment length polymorphisms (T-RFLP) and clone library analyses targeted at bacterial 16S rRNA genes. The results show that: (1) the libraries of the two waterweeds contain wide phylogenetic distribution of bacteria, and that the sequences of the two libraries can be separated into 93 OTUs (at 97% similar value); (2) Betaproteobacteria, including Burkholderiales, was the most abundant bacterial group on both plants. Cyanobacteria and Gammaproteobacteria were the second largest groups on V. natans and H. verticillata, respectively. Both clone libraries included some sequences related to those of methanotrophs and nitrogen-fixing bacteria; (3) Cluster analysis of the T-RFLP profiles showed two distinct clusters corresponding to the two plant populations. Both ANOSIM of the T-RFLP data and Libshuff analysis of the two clone libraries indicated a significant difference in epiphytic bacterial communities between the two plants. Therefore, the epiphytic bacterial communities on submerged macrophytes appear to be diverse and host-specific, which may aid in understanding the ecological functions of submerged macrophytes in general.

Isolation and identification of bacteria associated with the surfaces of several algal species

We conducted this study to assess the diversity of bacteria associated with the surfaces of algae based on 16S rDNA sequence analyses.Twelve strains of bacteria were obtained from the surfaces of the following four species of algae:Gracilaria textorii,Ulva pertusa,Laminaria japonica,and Polysiphonia urceolata.The isolated strains of bacteria can be divided into two groups:Halomonas and Vibrio,in physiology,biochemical characteristics and 16S rDNA sequence analyses.The phylogenetic tree constructed based on 16S rDNA sequences of the isolates shows four obvious clusters,Halomonas venusta,Vibrio tasmaniensis,Vibrio lentus,and Vibrio splendidus.Isolates from the surface of P.urceolata are more abundant and diverse,of which strains P9 and P28 have a 16S rDNA sequence very similar(97.5%-99.8%) to that of V.splendidus.On the contrary,the isolates from the surfaces of G.textorii,U.pertusa and L.japonica are quite simple and distribute on different branches of the phylogenetic tree.In overall,the results of this study indicate that the genetic relationships among the isolates are quite close and display a certain level of host species specificity,and alga-associated bacteria species are algal species specific.

Epiphytic orchids and their ecological niche under anthropogenic influence in central Himalayas,Nepal

The survival chance of epiphytie orchids today not only depends on the natural site conditions required by the orchids but also on anthropogenic changes in site conditions. This study answers two questions： （1） What is the ecological niche of the different epiphytic orchid species？ （2） What are the ecological factors that threaten epiphytic orchid＇s population under anthropogenic disturbances？ Our study area was the Kathmandu valley, Nepal, with its subtropical forest. We established 156 systematically selected sampling points in the Kathmandu area covering different types of ecosystems under human impacts such as densely populated area, agricultural land, mixed agricultural and settled area, old tree patches, and a natural forest in a national park. The ecological niche of the orchid species was analyzed with a principal component analysis （PCA）. The correlations between the different site factors were statistically significant. Spearman＇s rank correlation matrices showed that the variables land-use intensities with altitude, and height with diameter in breast height （dbh） of host had the highest significant positive correlation coefficient （0.67 and 0.64 respectively）. On the other hand, host bark pH and altitude as well as land use had a significantly strong negative correlation coefficient （-0.80 and -0.61, respectively）. Different epiphytic orchid species interact differently with the given set of environmental factors： for occurrence of Vanda cristata there is no single environmental factor of special influence, while for Rhynehostylis retusa high bark pH and high light availability are important. First two axis of the PCA explained more than 50% of the total variance. Most orchid species occupy a specific, narrow niche in this ecological space. The main causes of anthropogenie influence of orchid population in the Kathmandu Valley are loss of adequate host trees （species and size） and increasing air pollution, resulting in increasing host bark pH.

Ecological damage of submerged macrophyte Myriophyllum spicatum by cell extracts from microcystin(MC)-and non-MC-producing cyanobacteria,Microcystis

To explore how decomposed Microcystis-dominant cyanobacterial blooms affect submerged macrophytes,the submerged plant Myriophyllum spicatum was exposed to cell extracts from microcystin(MC)-and non-MC-producing Microcystis strains in a laboratory experiment.Results showed that both Mcracystis cell extracts exerted obvious damages to plant biomass,photosynthesis,primary and secondary metabolism measures,and resistance of plant antioxidant systems,with MC-producing Microcystis having stronger effects due to the presence of MCs.Cyanotoxins other than MCs responsible for the negative effects from both strains needs further identification.The Shannon diversity and Chao1 indices of epiphytic and planktonic bacteria were decreased by the cell extracts from both Microcystis strains.However,epiphytic and planktonic bacterial communities responded differently to cell extracts at the genus level.The dominant genera of planktonic bacteria including Enterobacter,Pseudomonas,and Novosphingobium from phylum Proteobacteria,Chryseobacterium from phylum Bacteroidetes,and Microbacterium from Actinobacteriota in the treatments with cell extracts were previously reported to have strains with algicidal and MC-degrading capabilities.B acterial genes associated with energy production and conversion,amino acid transport and metabolism,and inorganic ion transport and metabolism,were more abundant in both treatments than the control for planktonic bacteria,but less abundant for epiphytic bacteria.We speculate that planktonic bacterial communities have the potential to use and degrade substances derived from Microcystis cell extracts,which may be beneficial for M.spicatum to alleviate damages from Microcystis.Further research is needed to verify the structure and function dynamics of epiphytic and planktonic bacteria in the interaction between cyanobacteria and submerged macrophytes.