Diversity patterns of seasonal wetland plant communities mainly driven by rare terrestrial species

In cleared landscapes, wetlands can represent important reservoirs of native plant diversity, which include terrestrial species. Depending on study aims, non-wetland plants might be removed before analysis, affecting conclusions around biodiversity and community structure. We compared the native plant communities of seasonal wetlands in a predominately agricultural landscape as defined geographically (including all species) with that of the obligate wetland assemblage. We were primarily concerned with determining how this design decision affects ecological and conservation conclusions. We analysed a survey database containing >12,900 flora records from South Australia, developing a new area-based method to remove sampling bias to include only wetlands with a near-complete census. We modelled occupancy, species-area relationships, β-diversity and nestedness under our contrasting community definitions. Terrestrial species were 57.4 % of total richness. Removing these species reduced wetland α-diversity by 45 %, but did not affect the scaling of richness with area (power-law species-area relationship z = 0.21 ± 0.01). Occupancies for wetland plants were relatively uniform, but were heavily dominated by rare (satellite) species when terrestrial plants were included, and this also increased β-diversity. Nestedness for terrestrial species occupancies was marginally lower than predicted under null models, suggesting that rare species often do not co-occur with common species. An implication of these occupancy patterns is that twice as many wetlands (and 50 % more wetland area) would be needed to include every native species within at least one wetland compared with wetland-only species.     

Dune soil communities primarily associated with climate factors,not exotic plant presence

Plant and Soil - Soil communities are shaped by multiple biotic and environmental components. We assessed the role of multiple factors in shaping soil bacterial and nematode communities in an...     

Gas exchange of terrestrial and epiphytic orchids from Brazilian Atlantic Rainforest

Leaf gas exchange of terrestrial and epiphytic orchids from the Atlantic Rainforest in northeast Brazil was investigated under artificial growth conditions. The terrestrial orchids showed higher values of all photosynthetic parameters in comparison to epiphytic ones. There was a close relationship between P _N and g _s for both terrestrial and epiphytic orchids. Taken together, our results demonstrated that the photosynthetic parameters were related to the specific growth habits of the orchids under study.     

Succession of plant communities and soil development

Changes of plant communities (or biotic communities) are classified according to their causes. The term succession is restricted inClements' original sense to gradual directional replacemental changes of phytocenoses (or biocenoses) caused by their reaction upon the environment including soil development and a classification of succession is proposed. Gradual changes of communities caused by external factors are termed adaptive changes. The connection between succession and soil development as a unified process as well as the concept of climax as its result are discussed. A brief historical survey of the theory of succession as well as soil development is presented and definitions of some successional terms are proposed.     

Associational plant refuges: convergent patterns in marine and terrestrial communities result from differing mechanisms

Summary An associational plant refuge occurs when a plant that is susceptible to herbivory gains protection from herbivory when it is associated with another plant. In coastal North Carolina, the abundance of the palatable red alga Gracilaria tikvahiae is positively correlated with the abundance of the unpalatable brown alga Sargassum filipendula during times of increased herbivore activity. To see if grazing by the sea urchin Arbacia punctulata could generate this pattern, controlled experiments were conducted in out-door microcosms and in the laboratory. Gracilaria beneath a canopy of Sargassum was eaten significantly less than Gracilaria alone. When Arbacia were excluded, Gracilaria alone grew significantly more than Gracilaria beneath Sargassum, demonstrating that Sargassum is a competitor of Gracilaria. Experiments investigating Sargassum's deterrent role indicated that Sargassum decreased the foraging range of Arbacia and the rate at which it fed on Gracilaria. Additional experiments with plastic Sargassum mimics indicated that the decreased grazing on Gracilaria was not a result of Sargassum morphology, but was probably attributable to some chemical characteristic of Sargassum. The pattern of increased grazing in monocultures (only Gracilaria present) versus polycultures (both Gracilaria and Sargassum present) demonstrated in this study also has been demonstrated for plant-insect interactions in terrestrial communities. In these communities, insect density is higher in monocultures than in polycultures because insects find and immigrate to monocultures more rapidly, and once in a monoculture, they emigrate from them less often than from polycultures. In this study, urchins did not find and immigrate to monocultures more rapidly, nor did they tend to stay in them once they were found; in fact, they emigrated from monocultures of Gracilaria more rapidly than from Gracilaria and Sargassum polycultures. Increased grazing in Gracilaria monocultures resulted from increased rates of movement and feeding of individual herbivores, not from increased herbivore density as has been reported for terrestrial systems.     

Seasonal development of annual shoots in some terrestrial orchids from Russia and Japan

Annual shoots of 46 terrestrial orchid species commonly found in wide ranges of temperate climates in Russia and Japan change their patterns of growth recurrence from the dormancy state, through formation and growth, to the next dormancy state during the course of yearly response to seasonal cycles of environmental conditions. Each of the species has its own strategy in seasonal development of aerial shoots, rhizomes, tubers and roots, and shows seasonal differentiation of shoot morphogenesis at the early stage of new shoot apex formation in accordance with its growth habit, habitat and range size of geographical distribution. Perennial orchids with sympodial growth patterns and primitive life forms are characterized by long duration of shoot and inflorescence development inside the bud. Among the species studied, the orchids that have annually regenerating root-stem tubers have the shortest duration of root and shoot morphogenesis. The species that have predominant patterns of monopodial growth show variability in duration of lateral shoot growth due to the energy budget of the mother plant. The species which have latitudinally long ranges of distribution from northern colder regions to southern warmer regions tend to take longer for shoot development inside the bud, and aerial shoots have a shorter life-span in the northern regions than those in the south.     

Effects of invasive aquatic carrion on soil chemistry and terrestrial microbial communities

Carrion plays a crucial role in the recycling of nutrients and organic matter in ecosystems. Yet, despite their ecological importance, studies addressing the relevance of carrion originated from invasive alien species (IAS) in the interface between aquatic and terrestrial ecosystems are uncommon, especially those assessing belowground effects. In this study, we carried out a manipulative experiment to assess the impact of massive mortalities of the Asian clam Corbicula fluminea (Müller, 1774) as a carrion subsidy evaluating possible effects on the terrestrial soil chemistry and the structure of a microbial (bacteria and fungi) community. We placed five levels of C. fluminea density (0, 100, 500, 1000 and 2000 ind. m^?2) and samples were collected 7, 30 and 90 days after clams’ addition. The results revealed that C. fluminea carrion have a significant effect belowground, especially on nutrients content (mainly NH₄ ⁺, NO₂ ^?, NO₃ ^? and PO₄ ^3?), fungal biomass and fungal and bacterial diversity. Given the predicted increase and intensification of extreme climatic events and the widespread distribution of several aquatic IAS (including bivalve species such as C. fluminea) the ecological importance of these massive mortalities (and resulting carrion) cannot be ignored because they may affect microbial communities with significant impacts on nutrient cycling, even in adjacent terrestrial habitats.     

Impact of warming and timing of snow melt on soil microarthropod assemblages associated with Dryas-dominated plant communities on Svalbard

Open Top Chambers (OTCs) were used to measure impacts of predicted global warming on the structure of the invertebrate community of a Dryas octopetala heath in West Spitsbergen. Results from the OTC experiment were compared with natural variation in invertebrate community structure along a snowmelt transect through similar vegetation up the adjacent hillside. Changes along this transect represent the natural response of the invertebrate community to progressively longer and potentially warmer and drier growing seasons. Using MANOVA, ANOVA, Linear Discriminant Analysis and χ² tests, significant differences in community composition were found between OTCs and controls and among stations along the transect. Numbers of cryptostigmatic and predatory mites tended to be higher in the warmer OTC treatment but numbers of the aphid Acyrthosiphon svalbardicum , hymenopterous parasitoids, Symphyta larvae, and weevils were higher in control plots. Most Collembola, including Hypogastrura tullbergi , Lepidocyrtus lignorum and Isotoma anglicana , followed a similar trend to the aphid, but Folsomia bisetosa was more abundant in the OTC treatment. Trends along the transect showed clear parallels with the OTC experiment. However, mite species, particularly Diapterobates notatus , tended to increase in numbers under warming, with several species collectively increasing at the earlier exposed transect stations. Overall, the results suggest that the composition and structure of Arctic invertebrate communities associated with Dryas will change significantly under global warming.     

Characterizing soil seed banks and relationships to plant communities

Estimates of soil seed banks are important to many ecological investigations and plant conservation, yet seed banks are among the most difficult plant community attributes to accurately quantify. To compare extraction and emergence seed bank characterization methods, we collected 0- to 5-cm soil seed bank samples and measured plant community composition in six microsite types (below different perennial plant species and interspaces) at 10 field sites in the Mojave Desert, USA. Extraction detected five times more species sample^?1 and orders of magnitude greater seed density than emergence, though evaluating viability of extracted seed was not straightforward. Only 13 % of 847 tested seeds from extraction emerged in follow-up assays. Considering all sites, species detection was more similar between methods: 21 taxa for emergence and 28 for extraction. Results suggest that: (i) capturing microsite variation is critical for efficiently estimating site-level desert seed banks; (ii) method comparisons hinged on the scale of analysis for species richness, as differences in species detection between methods diminished when increasing resolution from the sample to the regional scale; (iii) combining data from all seed bank methods provided the strongest correlation with vegetation; and (iv) improving knowledge of seed germinability is important for advancing both seed bank methods, including for extraction to evaluate the proportion of extracted seeds that are viable. Multifactor approaches that balance several effectiveness measures (e.g., both seed density and species detection at multiple scales) and procedural challenges are most likely to accurately represent complexity in tradeoffs for choosing methods to quantify soil seed banks.     

Fungal communities associated with degradation of polyester polyurethane in soil

Soil fungal communities involved in the biodegradation of polyester polyurethane (PU) were investigated. PU coupons were buried in two sandy loam soils with different levels of organic carbon: one was acidic (pH 5.5), and the other was more neutral (pH 6.7). After 5 months of burial, the fungal communities on the surface of the PU were compared with the native soil communities using culture-based and molecular techniques. Putative PU-degrading fungi were common in both soils, as <45% of the fungal colonies cleared the colloidal PU dispersion Impranil on solid medium. Denaturing gradient gel electrophoresis showed that fungal communities on the PU were less diverse than in the soil, and only a few species in the PU communities were detectable in the soil, indicating that only a small subset of the soil fungal communities colonized the PU. Soil type influenced the composition of the PU fungal communities. Geomyces pannorum and a Phoma sp. were the dominant species recovered by culturing from the PU buried in the acidic and neutral soils, respectively. Both fungi degraded Impranil and represented >80% of cultivable colonies from each plastic. However, PU was highly susceptible to degradation in both soils, losing up to 95% of its tensile strength. Therefore, different fungi are associated with PU degradation in different soils but the physical process is independent of soil type.     

Putative new plant viruses associated with Plasmopara viticola-infected grapevine samples

In this study, we analysed a total of 16 libraries from over 150 grapevine leaf and grape samples infected with Plasmopara viticola (downy mildew of grapevine) to characterise the virome associated to this oomycete. Samples were collected in five distinct regions in Italy and in four different regions in Spain, representative of different pedoclimatic conditions and different grapevine cultivars during 2018 growing season. Due to the metagenomics nature of the samples (containing at least both downy mildew hyphae and spores, and grapevine cells residues), we were able to assemble several plant viruses and a few possible novel plant virus genomes with our in silico analysis. We detected several plant virus variants already reported in grapevine, and a putative new ilarvirus previously unreported in grapevine. Furthermore, we characterised three new phenui-like viruses (in the order Bunyavirales), one of which shares some commonalities with plant coguviruses. Finally, we report a new strict association of three viral segments (one flavi-like and two virga-like) that we propose to be a new virus taxon named jivivirus.     

Above- and belowground insect herbivores differentially affect soil nematode communities in species-rich plant communities

Interactions between above‐ and belowground invertebrate herbivores alter plant diversity, however, little is known on how these effects may influence higher trophic level organisms belowground. Here we explore whether above‐ and belowground invertebrate herbivores which alter plant community diversity and biomass, in turn affect soil nematode communities. We test the hypotheses that insect herbivores 1) alter soil nematode diversity, 2) stimulate bacterial‐feeding and 3) reduce plant‐feeding nematode abundances. In a full factorial outdoor mesocosm experiment we introduced grasshoppers (aboveground herbivores), wireworms (belowground herbivores) and a diverse soil nematode community to species‐rich model plant communities. After two years, insect herbivore effects on nematode diversity and on abundance of herbivorous, bacterivorous, fungivorous and omni‐carnivorous nematodes were evaluated in relation to plant community composition. Wireworms did not affect nematode diversity despite enhanced plant diversity, while grasshoppers, which did not affect plant diversity, reduced nematode diversity. Although grasshoppers and wireworms caused contrasting shifts in plant species dominance, they did not affect abundances of decomposer nematodes at any trophic level. Primary consumer nematodes were, however, strongly promoted by wireworms, while community root biomass was not altered by the insect herbivores. Overall, interaction effects of wireworms and grasshoppers on the soil nematodes were not observed, and we found no support for bottom‐up control of the nematodes. However, our results show that above‐ and belowground insect herbivores may facilitate root‐feeding rather than decomposer nematodes and that this facilitation appears to be driven by shifts in plant species composition. Moreover, the addition of nematodes strongly suppressed shoot biomass of several forb species and reduced grasshopper abundance. Thus, our results suggest that nematode feedback effects on plant community composition, due to plant and herbivore parasitism, may strongly depend on the presence of insect herbivores.     

Germination responses of four native terrestrial orchids from south-west Western Australia to temperature and light treatments

We report an investigation into the impact of temperature and illumination on in vitro symbiotic and asymbiotic germination of the threatened taxon Caladenia huegelii, and three other orchid spp. namely—Caladenia latifolia, Microtis media and Pterostylis sanguinea, all species from south-west Western Australia, a recognized biodiversity hotspot. High symbiotic germination on oatmeal agar (OMA + fungal symbionts specific to each species) was recorded in three species in continuous dark incubation i.e. C. huegelii seeds (98 % germination at 25 °C), and M. media and P. sanguinea (93 and 98 % respectively at 20 °C). Highest symbiotic germination for C. latifolia (100 %) was observed at 15 and 20 °C under light treatment (12/12 h light/dark). Low temperature incubation (10 °C) significantly suppressed symbiotic germination/development of seedlings across all species. Asymbiotic media treatments assessed (OMA minus fungal symbionts, Pa₅ and ½ MS), failed to stimulate any germination with C. latifolia seeds at 20 °C in either light or dark treatments after an 8 week incubation period. Seeds of M. media sown onto ½ MS medium resulted in higher germination in all developmental stages (3–5) in dark treatment than OMA and Pa₅. Seeds of P. sanguinea sown onto ½ MS medium resulted in higher overall germination in all developmental stages (3–5) in light and dark incubation compared to OMA and Pa₅. OMA supported the highest asymbiotic germination (100 %) in both light and dark incubation with M. media (only to stage 3) but did not support germination and development with other spp. tested. Caladenia huegelii seeds reached developmental Stage 3 (i.e. germinated), but only on Pa₅ medium and only at a relatively low rate in either light (2.6 %) or dark (2.1 %). Germination was higher and development of seedlings faster overall in all test species in symbiotic compared with asymbiotic media treatments. P. sanguinea seeds demonstrated the best response (among species tested) to asymbiotic germination on ½ MS with 40–53 % of germinated seeds spread over developmental stages 3–5 in light or dark incubation (at 20 °C) respectively. Illumination had no effect on fungal symbiont growth across all species, however incubation temperature treatments (10, 15, 20 and 25 °C) affected fungal growth rate. Growth of the fungal symbionts of C. huegelii, M. media and C. latifolia demonstrated significantly lower activity at 10 °C, but the cumulative radial growth rate of the P. sanguinea fungal symbiont reached 64 cm² after only 2 weeks at all temperatures tested, including 10 °C. The study highlights differences in symbiotic and aysmbiotic germination and early protocorm development in vitro between co-occurring herbaceous terrestrial Australian orchid taxa in response to variations in basal media, temperature and light.     

Widespread fluorescence in terrestrial and marine samples investigated from India

The discovery of green fluorescent protein (GFP) from jellyfish Aequorea victoria has provoked numerous studies to unveil the myriads of biomedical applications. Consequently, several studies also revealed the prevalence of fluorescence in different marine and terrestrial organisms. However, since GFP's discovery or the Nobel prize award on GFP, the fluorescence has not been explored so far from India. The current study presents the widespread fluorescent organisms resources available in India for biomedical and toxicological applications. Fluorescence emission from different plant and animal components were examined by direct observations using UV torchlight. Investigation revealed that blue light excited fluorescence in several organisms. For the first time, this study observed GFP like fluorescence in many terretrial and marine organisms of India. Observations are indicating that fluorescent proteins have essential ecological functions that are yet to be determined. The examined plant and animal components were not bioluminescent. In comparison, the potential untouched research areas on fluorescence aspects are detailed. A thorough review of fluorescent organisms reported hitherto is also provided to spread the current knowledge on fluorescence.     

辽宁省9种兰科植物根内与根际土壤中真菌群落结构的差异

兰科植物的生存及生长高度依赖其根中的共生真菌, 其中的菌根真菌更是对兰科植物的种子萌发与后续生长有着非常重要的作用, 研究兰科植物根中的真菌, 尤其是菌根真菌, 对兰科植物的保护有重要作用。该研究利用第二代测序技术, 对中国辽宁省境内的9种属于极小种群的兰科植物的根、根际土和根围土中的真菌群落和菌根真菌组成进行了研究。结果显示, 兰科植物根中的真菌群落和根际土、根围土中的真菌群落具有显著差异。兰科植物根中的总操作分类单元(OTU)数目远小于根际土和根围土中的总OTU数目。同时, 兰科植物根中菌根真菌的种类和丰度与根际土、根围土中菌根真菌的种类与丰度没有明显联系。FunGuild分析结果显示, 丛枝菌根真菌在根际土与根围土中的丰度非常高, 但在兰科植物的根中却数量极少。这些结果表明, 兰科植物根中的真菌群落与土壤中的真菌群落在一定程度上是相互独立的。