Harnessing the power of microbes: Enhancing soybean growth in an acidic soil through AMF inoculation rather than P-fertilization.

The low phosphorus (P) availability of acidic soils severely limits leguminous plant growth and productivity. Improving the soil P nutritional status can be achieved by increasing the P-content through P-fertilization or stimulating the mineralization of organic P via arbuscular mycorrhizal fungi (AMF) application; however, their corresponding impacts on plant and soil microbiome still remain to be explored. Here, we examined the effects of AMF-inoculation and P-fertilization on the growth of soybean with different P-efficiencies, as well as the composition of rhizo-microbiome in an acidic soil. The growth of recipient soybean NY-1001, which has a lower P-efficiency, was not significantly enhanced by AMF-inoculation or P-fertilization. However, the plant biomass of higher P-efficiency transgenic soybean PT6 was significantly increased by 46.74%-65.22% through AMF-inoculation. Although there was no discernible difference in plant biomass between PT6 and NY-1001 in the absence of AMF-inoculation and P-fertilization, PT6 had approximately 1.9-2.5 times the plant biomass of NY-1001 after AMF-inoculation. Therefore, the growth advantage of higher P-efficiency soybean was achieved through the assistance of AMF rather than P-fertilization in available P-deficient acidic soil. Most nitrogen (N)-fixing bacteria and some functional genes related to N-fixation were abundant in endospheric layer, as were the P-solubilizing Pseudomonas plecoglossicida, and annotated P-metabolism genes. These N-fixing and P-solubilizing bacteria were positive correlated with each other. Lastly, the two most abundant phytopathogenic fungi species accumulated in endospheric layer, they exhibited positive correlations with N-fixing bacteria, but displayed negative interactions with the majority of the other dominant non-pathogenic genera with potential antagonistic activity.

Insect root feeders incur negative density-dependent damage across plant species in an alpine meadow.

Although herbivores are well known to incur positive density-dependent damage and mortality, thereby likely shaping plant community assembly, the response of belowground root feeders to changes in plant density has seldom been addressed. Locally rare plant species (with lower plant biomass per area) are often smaller with shallower roots than common species (with higher plant biomass per area) in competition-intensive grasslands. Likewise, root feeders are often distributed in the upper soil layers. We hypothesized, therefore, that root feeders would incur negative density (biomass)-dependent damage across plant species. To test this hypothesis, we investigated the diversity and abundance of plant and root feeder species in an alpine meadow and determined the diet of the root feeders using metabarcoding. Across all species, root feeder load decreased with increasing aboveground plant biomass, root biomass, and total plant biomass per area, indicating a negative density dependence of damage across plant species. Aboveground plant biomass per area increased with increasing individual plant biomass and root depth per area across species, suggesting that rare plant species were smaller in size and had shallower root systems compared to common plant species. Both root biomass per area and root feeder biomass per area decreased with soil depth, but the root feeder biomass decreased disproportionately faster compared to root biomass with increasing root depth. Root feeder load decreased with increasing root depth but was not correlated with the feeding preference of root feeder species. Moreover, the prediction derived from a random process incorporating vertical distributions of root biomass and root feeder biomass significantly accounted for interspecific variation in root feeder load. In conclusion, the data indicate that root feeders incur negative density-dependent damage across plant species. On this basis, we suggest that manipulative experiments should be conducted to determine the effect of the negative density-dependent damage on plant community structure and that different types of plant-animal interactions should be concurrently examined to fully understand the effect of plant density on overall herbivore damage across plant species.

Triple-transgenic soybean in conjunction with glyphosate drive patterns in the rhizosphere microbial community assembly.

Plant roots continuously influence the rhizosphere, which also serves as a recruitment site for microorganisms with desirable functions. The development of genetically engineered (GE) crop varieties has offered unparalleled yield advantages. However, in-depth research on the effects of GE crops on the rhizosphere microbiome is currently insufficient. We used a triple-transgenic soybean cultivar (JD606) that is resistant to insects, glyphosate, and drought, along with its control, ZP661, and JD606 treated with glyphosate (JD606G). Using 16S and ITS rDNA sequencing, their effects on the taxonomy and function of the bacterial and fungal communities in the rhizosphere, surrounding, and bulk soil compartment niches were determined. Alpha diversity demonstrated a strong influence of JD606 and JD606G on bacterial Shannon diversity. Both treatments significantly altered the soil's pH and nitrogen content. Beta diversity identified the soil compartment niche as a key factor with a significant probability of influencing the bacterial and fungal communities associated with soybeans. Further analysis showed that the rhizosphere effect had a considerable impact on bacterial communities in JD606 and JD606G soils but not on fungal communities. Microbacterium, Bradyrhizobium, and Chryseobacterium were found as key rhizobacterial nodes. In addition, the LEfSe analysis identified biomarker taxa with plant-beneficial attributes, demonstrating rhizosphere-driven microbial recruitment. FUNGuild, Bugbase, and FAPROTAX functional predictions showed that ZP661 soils had more plant pathogen-associated microbes, while JD606 and JD606G soils had more stress-tolerance, nitrogen, and carbon cycle-related microbes. Bacterial rhizosphere networks had more intricate topologies than fungal networks. Furthermore, correlation analysis revealed that the bacteria and fungi with higher abundances exhibited varying degrees of positive and negative correlations. Our findings shed new light on the niche partitioning of bacterial and fungal communities in soil. It also indicates that following triple-transgenic soybean cultivation and glyphosate application, plant roots recruit microbes with beneficial taxonomic and functional traits in the rhizosphere.

Design, synthesis and biological evaluation of novel modified dual-target shikonin derivatives for colorectal cancer treatment.

Warburg effect provides energy and material essential for tumor proliferation, the reverse of Warburg effect provides insights into the development of a novel anti-cancer strategy. Pyruvate kinase 2 (PKM2) and pyruvate dehydrogenase kinase 1 (PDK1) are two key enzymes in tumor glucose metabolism pathway that not only contribute to the Warburg effect through accelerating aerobic glycolysis, but also serve as druggable target for colorectal cancer (CRC). Considering that targeting PKM2 or PDK1 alone does not seem to be sufficient to remodel abnormal glucose metabolism and achieve significant antitumor activity, a series of novel benzenesulfonyl shikonin derivatives were designed to regulate PKM2 and PDK1 simultaneously. By means of molecular docking and antiproliferative screen, we found that compound Z10 could act as the combination of PKM2 activator and PDK1 inhibitor, thereby significantly inhibited glycolysis that reshaping tumor metabolism. Moreover, Z10 could inhibit proliferation, migration and induce apoptosis in CRC cell HCT-8. Finally, the in vivo anti-tumor activity of Z10 was evaluated in a colorectal cancer cell xenograft model in nude mice and the results demonstrated that Z10 induced tumor cell apoptosis and inhibited tumor cell proliferation with lower toxicity than shikonin. Our findings indicated that it is feasible to alter tumor energy metabolism through multi-target synergies, and the dual-target benzenesulfonyl shikonin derivative Z10 could be a potential anti-CRC agent.

Parasitic flies alter the dietary preference of grasshoppers.

Parasitism is known to affect the behavior of host species to enhance parasite dispersal and transmission. However, host behavioral responses to parasitism unrelated to parasite dispersal and transmission have been much less studied. The objective of this study was to determine whether grasshopper hosts infected and uninfected with a parasitic fly (Blaesoxipha sp.) differ in terms of the nutrient content of the diet they consume. We investigated the dietary preferences of two grasshopper species (i.e. Asulconotus chinghaiensis and Chorthippus fallax) in terms of the C/N composition of plant species consumed, and determined whether this affected the egg production of unparasitized and parasitized grasshoppers by flies in a Tibetan alpine meadow. The composition of plants consumed differed significantly between the unparasitized and parasitized grasshoppers. Specifically, the abundance of N-rich legumes was lower and that of high C/N grasses was higher in the diet of the parasitized compared to the unparasitized grasshoppers. Diet N content was higher and C/N was lower in the diet of unparasitized grasshoppers, and parasitized females produced fewer eggs than their unparasitized conspecifics. Future enquiries are needed to understand the specific mechanisms underlying these dietary differences. The effects of parasites on the fitness-associated behavior of hosts should be studied more broadly to better understand parasite evolution and adaptation.

Moderate Grazing Promotes Arthropod Species Diversity in an Alpine Meadow.

Livestock grazing is an important tool used in grassland land management practices. Studies have substantially addressed the effect of grazing on plant species diversity, revealing that moderate grazing increases plant species diversity. However, few studies have dealt with the relationship between grazing and arthropod species diversity, which remains unclear. Here, we hypothesize that moderate grazing promotes arthropod species diversity because arthropods are directly or indirectly dependent on plant diversity. In this study, we conducted a two-year plant and arthropod survey from 2020 to 2021 at four levels of grazing intensity, i.e., nongrazing (as a control), light grazing, moderate grazing, and heavy grazing, of the long-term grazing experiment starting in 2016. The data show that plant species diversity peaked in the moderate grazing treatment, and herbivore species diversity was positively correlated with plant species diversity (and hence peaked in the moderate grazing treatment). Moderate grazing promoted parasitoid species diversity, which was positively correlated with herbivore species diversity. However, predator species diversity did not significantly differ among the four treatments. In addition, saprophage species diversity decreased, whereas coprophages increased with increasing grazing levels, such that species richness (but not species diversity of detritivores statistically) was highest in the moderate grazing treatment. Consequently, the species diversity of arthropods as a whole peaked at the moderate grazing level, a phenomenology that is consistent with the intermediate disturbance hypothesis. Considering that moderate grazing has been found to increase plant species diversity, facilitate soil carbon accumulation, and prevent soil erosion, we suggest that moderate grazing would maximize multi-functional ecosystem services.

Mycorrhizae Enhance Soybean Plant Growth and Aluminum Stress Tolerance by Shaping the Microbiome Assembly in an Acidic Soil.

Strongly acidic soils are characterized by high aluminum (Al) toxicity and low phosphorus (P) availability, which suppress legume plant growth and nodule development. Arbuscular mycorrhizal fungi (AMF) stimulate rhizobia and enhance plant P uptake. However, it is unclear how this symbiotic soybean-AMF-rhizobial trio promotes soybean growth in acidic soils. We examined the effects of AMF and rhizobium addition on the growth of two soybean genotypes, namely, Al-tolerant and Al-sensitive soybeans as well as their associated bacterial and fungal communities in an acidic soil. With and without rhizobial addition, AMF significantly increased the fresh shoot and root biomass of Al-tolerant soybean by 47%/87% and 37%/24%, respectively. This increase in plant biomass corresponded to the enrichment of four plant growth-promoting rhizobacteria (PGPR) in the rhizospheric soil, namely, Chitinophagaceae bacterium 4GSH07, Paraburkholderia soli, Sinomonas atrocyanea, and Aquincola tertiaricarbonis. For Al-sensitive soybean, AMF addition increased the fresh shoot and root biomass by 112%/64% and 30%/217%, respectively, with/without rhizobial addition. Interestingly, this significant increase coincided with a decrease in the pathogenic fungus Nigrospora oryzae as well as an increase in S. atrocyanea, A. tertiaricarbonis, and Talaromyces verruculosus (a P-solubilizing fungus) in the rhizospheric soil. Lastly, the compartment niche along the soil-plant continuum shaped microbiome assembly, with pathogenic/saprotrophic microbes accumulating in the rhizospheric soil and PGPR related to nitrogen fixation or stress resistance (e.g., Rhizobium leguminosarum and Sphingomonas azotifigens) accumulating in the endospheric layer. IMPORTANCE Taken together, this study examined the effects of arbuscular mycorrhizal fungi (AMF) and rhizobial combinations on the growth of Al-tolerant and Al-sensitive soybeans as well as their associated microbial communities in acidic soils and concluded that AMF enhances soybean growth and Al stress tolerance by recruiting PGPR and altering the root-associated microbiome assembly in a host-dependent manner. In the future, these findings will help us better understand the impacts of AMF on rhizosphere microbiome assembly and will contribute to the development of soybean breeding techniques for the comprehensive use of PGPR in sustainable agriculture.

Discrepancies in rhizobacterial assembly caused by glyphosate application and herbicide-tolerant soybean Co-expressing GAT and EPSPS.

There are concerns that the innovation of genetically modified herbicide-tolerant (GMHT) plants, as well as the application of herbicide to such GMHT plants, could have an impact on ecological interactions and unintentionally harm non-targeted organisms. Consequently, we intend to use full-length 16 S rDNA amplicon sequencing to examine changes in the bacterial community in the rhizosphere of GMHT soybean (Z106) harboring 5-enolpyruvylshikimate-3-phosphate synthase and Glyphosate N-acetyltransferase genes and GMHT soybean treated with glyphosate (Z106G). Glyphosate application significantly impacted bacterial alpha diversity (species richness, and Shannon diversity). Permutational multivariate analysis of variance of beta diversity demonstrated that soil compartments and growth stages had a substantial impact on soybean rhizobacterial communities (soil compartments, growth stages, P = 0.001). Community composition revealed that Z106G soils were abundant in Taibaiella and Arthrobacter pascens at maturity, while Chryseobacterium joostei and Stenotrophomonas maltophilia predominated in Z106 soils during flowering. Nitrogen-fixing and phosphate-solubilizing microbes were found in higher proportions in the rhizosphere than in bulk soil, with Sinorhizobium being more abundant in Z106 and Bacillus and Stenotrophomonas being more prevalent in Z106G rhizosphere soils. Collectively, our findings suggest glyphosate application and glyphosate-tolerant soybean as potential regulators of soybean rhizobacterial composition.

The host niches of soybean rather than genetic modification or glyphosate application drive the assembly of root-associated microbial communities.

Plant roots significantly influence soil microbial diversity, and soil microorganisms play significant roles in both natural and agricultural ecosystems. Although the genetically modified (GM) crops with enhanced insect and herbicide resistance are thought to have unmatched yield and stress resistance advantages, thorough and in-depth case studies still need to be carried out in a real-world setting due to the potential effects of GM plants on soil microbial communities. In this study, three treatments were used: a recipient soybean variety Jack, a triple transgenic soybean line JD321, and the glyphosate-treated JD321 (JD321G). Three sampling stages (flowering, seed filling and maturing), as well as three host niches of soybean rhizosphere [intact roots (RT), rhizospheric soil (RS) and surrounding soil (SS)] were established. In comparison to Jack, the rhizospheric soil of JD321G had higher urease activity and lower nitrite reductase at the flowering stage. Different treatments and different sampling stages existed no significant effects on the compositions of microbial communities at different taxonomic levels. However, at the genus level, the relative abundance of three plant growth-promoting fungal genera (i.e. Mortierella, Chaetomium and Pseudombrophila) increased while endophytic bacteria Chryseobacterium and pathogenic bacteria Streptomyces decreased from the inside to the outside of the roots (i.e. RT → RS → SS). Moreover, two bacterial genera, Bradyrhizobium and Ensifer were more abundant in RT than in RS and SS, as well as three species, Agrobacterium radiobacter, Ensifer fredii and Ensifer meliloti, which are closely related to nitrogen-fixation. Furthermore, five clusters of orthologous groups (COGs) associated to nitrogen-fixation genes were higher in RT than in RS, whereas only one COG annotated as dinitrogenase iron-molybdenum cofactor biosynthesis protein was lower. Overall, the results imply that the rhizosphere host niches throughout the soil-plant continuum largely control the composition and function of the root-associated microbiome of triple transgenic soybean.

The Photodegradation of Lignin Methoxyl C Promotes Fungal Decomposition of Lignin Aromatic C Measured with 13C-CPMAS NMR.

Solar radiation has been regarded as a driver of litter decomposition in arid and semiarid ecosystems. Photodegradation of litter organic carbon (C) depends on chemical composition and water availability. However, the chemical changes in organic C that respond to solar radiation interacting with water pulses remain unknown. To explain changes in the chemical components of litter organic C exposed to UV-B, UV-A, and photosynthetically active radiation (PAR) mediated by water pulses, we measured the chemistry of marcescent Lindera glauca leaf litter by solid-state 13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) over 494 days of litter decomposition with a microcosm experiment. Abiotic and biotic factors regulated litter decomposition via three pathways: first, photochemical mineralization of lignin methoxyl C rather than aromatic C exposed to UV radiation; second, the biological oxidation and leaching of cellulose O-alkyl C exposed to PAR and UV radiation interacts with water pulses; and third, the photopriming effect of UV radiation on lignin aromatic C rather than cellulose O-alkyl C under the interaction between radiation and water pulses. The robust decomposition index that explained the changes in the mass loss was the ratio of aromatic C to O-alkyl C (AR/OA) under radiation, but the ratio of hydrophobic to hydrophilic C (hydrophobicity), the carbohydrate C to methoxyl C ratio (CC/MC), and the alkyl C to O-alkyl C ratio (A/OA) under radiation were mediated by water pulses. Moreover, the photopriming effect and water availability promoted the potential activities of peroxidase and phenol oxidase associated with lignin degradation secreted by fungi. Our results suggest that direct photodegradation of lignin methoxyl C increases microbial accessibility to lignin aromatic C. Photo-oxidized compounds might be an additional C pool to regulate the stability of the soil C pool derived from plant litter by degrading lignin methoxyl and aromatic C.

Water table decline alters arthropod community structure by shifting plant communities and leaf nutrients in a Tibetan peatland.

Water table decline is one of the most serious environmental problems in the peatland in the Qinghai-Tibetan Plateau. However, the effect of water table decline on the structure of aboveground arthropod communities is still not clear. We investigated changes in the abundance of different arthropod groups, and estimated the abundance, height, and biomass of the plant community in a soil water table reduction experiment to reveal the effect of water table decline on the arthropod community structure. The effect of water level decline on herbivorous arthropods varied according to the feeding habits. Specifically, water table decline treatment decreased the abundance of grass-preferring herbivores but increased the abundance of forb-preferring herbivores. However, the density of predators (e.g., spiders) did not change significantly. The variations in arthropod communities were correlated with the increase in forbs and leaf nitrogen content in the water table decline treatments. Our experiment demonstrated that the effect of water table decline on plant communities cascades upwardly to alter the arthropod community. Such trophic interactions should be considered in studies aimed at predicting shifts in the arthropods communities in a changing climate.

Somatic Mutation Analysis in Salix suchowensis Reveals Early-Segregated Cell Lineages.

Long-lived plants face the challenge of ever-increasing mutational burden across their long lifespan. Early sequestration of meristematic stem cells is supposed to efficiently slow down this process, but direct measurement of somatic mutations that accompanies segregated cell lineages in plants is still rare. Here, we tracked somatic mutations in 33 leaves and 22 adventitious roots from 22 stem-cuttings across eight major branches of a shrub willow (Salix suchowensis). We found that most mutations propagated separately in leaves and roots, providing clear evidence for early segregation of underlying cell lineages. By combining lineage tracking with allele frequency analysis, our results revealed a set of mutations shared by distinct branches, but were exclusively present in leaves and not in roots. These mutations were likely propagated by rapidly dividing somatic cell lineages which survive several iterations of branching, distinct from the slowly dividing axillary stem cell lineages. Leaf is thus contributed by both slowly and rapidly dividing cell lineages, leading to varied fixation chances of propagated mutations. By contrast, each root likely arises from a single founder cell within the adventitious stem cell lineages. Our findings give straightforward evidence that early segregation of meristems slows down mutation accumulation in axillary meristems, implying a plant "germline" paralog to the germline of animals through convergent evolution.

Climate change affects detritus decomposition rates by modifying arthropod performance and species interactions.

Climate change can indirectly affect ecosystem functions including detritus decomposition by modifying physiological traits, feeding behavior, and species interactions (including consumptive and non-consumptive top-down cascading effects) of decomposing arthropods. It is known that the effect of climate change on decomposition can be negative, neutral, or positive, and that it is highly context-dependent, depending on detritus quality, species identity, species interactions, and ecosystem type. Thus, ongoing climate change will undoubtedly influence the effects of arthropods on decomposition rates. More comprehensive studies are urgently needed to elucidate the effect of climate change on arthropod-detritus decomposers, particularly in the context of the decomposition of animal droppings and carrion.

Rare plant species are at a disadvantage when both herbivory and pollination interactions are considered in an alpine meadow.

Rare plant species often suffer less damage than common species because of positive density-dependent herbivory, and it has been suggested that this 'rare species advantage' fosters plant species coexistence. However, it is unknown whether rare species have an advantage when pollination interactions are also considered. We hypothesized that a 'positive density-dependent pollination success' across plant species would result in common plants experiencing higher seed set rates compared to rare species, and that positive density-dependent effects would negate or even override the positive density-dependent damage due to herbivory resulting in higher seed loss rates in common plant species. We tested this hypothesis by concurrently examining a plant-predispersal seed predator system and a plant-pollinator system for 24 Asteraceae species growing in an alpine meadow community (Sichuan Province, China). Having previously reported a positive density-dependent effect on seed loss rates due to seed predators, we here focus on the density-dependent effects on pollination success by investigating pollinator species richness, visitation frequencies and seed set rates for each plant species. We also estimated the seed output rate of each plant species as the product of seed set rate and the rate of surviving seeds (i.e. 1 - the seed loss rate). Consistent with our hypothesis, a positive density-dependent effect was observed for pollinator species richness, visitation frequencies and seed set rates across plant species. Moreover, the positive effect overrode the negative density-dependent effect of herbivores on seed production, such that common species tended to have a higher seed output rate than rare species (i.e. we observed a 'rare species disadvantage'). These results indicate that the low seed output rate of rare species might result from a pollination limitation, and that both mutualistic and antagonistic interactions should be examined simultaneously to fully understand plant species coexistence in local communities.

Effects of norfloxacin on decomposition and nutrient release in leaves of the submerged macrophyte Vallisneria natans (Lour.) Hara.

It is well known that antibiotic residuals affect the composition and structure of microbial communities. However, the consequences of these biological changes in terms of ecosystem function remain poorly understood, particularly in aquatic ecosystems. Here, we investigated the impacts of norfloxacin (NOR, 0, 0.5, and 8 mg L-1), a widely used antibiotic, on the microbial community structure on leaf surfaces of the submerged macrophyte Vallisneria natans, and the corresponding variations in litter decomposition, litter nutrient release, and water properties. Results showed that after 40 days of exposure, bacterial richness consistently decreased with increasing NOR concentration, and that richness of fungi was significantly lower in treatments adding NOR than in the control treatment. Moreover, NOR shifted the community toward NOR resistant phyla and genera, especially in the bacteria community. These community shifts resulted in the inhibition of litter decomposition and nutrient release from leaf litter to system water, accompanied by increases in dissolved oxygen concentration and pH of system water. Our results indicate that, by affecting microbial communities, NOR had significant effects on litter decomposition, litter nutrient release, and water properties, highlighting the potential harmful effects of NOR on aquatic ecosystem function.

Linkage between species traits and plant phenology in an alpine meadow.

Plant phenology differs largely among coexisting species within communities that share similar habitat conditions. However, the factors explaining such phenological diversity of plants have not been fully investigated. We hypothesize that species traits, including leaf mass per area (LMA), seed mass, stem tissue mass density (STD), maximum plant height (Hmax), and relative growth rate in height (RGRH), explain variation in plant phenology, and tested this hypothesis in an alpine meadow. Results showed that both LMA and STD were positively correlated with the onset (i.e., beginning) and offset (i.e., ending) times of the four life history events including two reproductive events (flowering and fruiting) and two vegetative events (leafing and senescing). In contrast, RGRH was negatively correlated with the four life phenological events. Moreover, Hmax was positively correlated with reproductive events but not with vegetative events. However, none of the eight phenological events was associated with seed size. In addition, the combination of LMA and STD accounted for 50% of the variation in plant phenologies. Phylogenetic generalized least squares analysis showed plant phylogeny weakened the relationships between species traits vs. phenologies. Phylogeny significantly regulated the variation in the ending but not the beginning of phenologies. Our results indicate that species traits are robust indicators for plant phenologies and can be used to explain the diversity of plant phenologies among co-occurring herbaceous species in grasslands. The findings highlight the important role of the combination of and trade-offs between functional traits in determing plant phenology diversity in the alpine meadow.

Plant volatiles mediate evolutionary interactions between plants and tephritid flies and are evolutionarily more labile than non-volatile defenses.

Studies show that plant defenses influence the host-use of herbivores and tend to be evolutionarily more labile than herbivore traits (e.g. feeding preferences). However, all previous studies have focused exclusively on non-volatile plant defenses thereby overlooking the roles of plant volatiles. We hypothesized that volatiles are equally important determinants of herbivore host-use and are evolutionarily more labile than herbivore traits. To test these hypotheses, the following experiments were conducted. We identified the volatiles and non-volatiles of 17 Asteraceae species and measured their relative contents. We also used a highly resolved bipartite trophic network of the 17 host species and 20 herbivorous (pre-dispersal seed predator) tephritid fly species to determine the evolutionary interactions between plants and herbivores. The chemical data showed that interspecific similarity in volatiles-but not non-volatiles and phylogenetic distance-significantly accounted for the herbivore community across the plant species; this implies that plant volatiles-but not non-volatile compounds and species identity-dictate plant-tephritid fly interactions. Moreover, we observed phylogenetic signal for non-volatiles but not for volatiles; therefore closely related herbivores do not necessarily use closely related host species with similar non-volatiles, but do tend to attack plants producing similar volatiles. Thus, plant volatiles are evolutionarily more labile than non-volatiles and herbivore traits associate with host use. These results show that the interactions between plants and herbivores are evolutionary asymmetric, shed light on the role of plant volatiles in plant-herbivore interactions, and highlight the need to include data for both volatiles and non-volatiles when investigating plant-animal interactions.

Responses of Plant Reproductive Phenology to Winter-Biased Warming in an Alpine Meadow.

Climate warming is often seasonally asymmetric with a higher temperature increase toward winters than summers. However, the effect of winter-biased warming on plant reproductive phenology has been seldom investigated under natural field conditions. The goal of this study was to determine the effects of winter-biased warming on plant reproductive phenologies. In an alpine meadow of Tibetan Plateau, we deployed six large (15 m × 15 m × 2.5 m height) open top chambers (three warmed chambers and three non-warmed chambers) to achieve winter-biased warming (i.e., a small increase in annual mean temperature with a greater increase towards winter than summer). We investigated three phenophases (onset and offset times and duration) for both the flowering and fruiting phenologies of 11 common species in 2017 and 8 species in 2018. According to the vernalization theory, we hypothesized that mild winter-biased warming would delay flowering and fruiting phenologies. The data indicated that the phenological responses to warming were species-specific (including positive, neutral, and negative responses), and the number of plant species advancing flowering (by averagely 4.5 days) and fruiting onset times (by averagely 3.6 days) was higher than those delaying the times. These changes were inconsistent with the vernalization hypothesis (i.e. plants need to achieve a threshold of chilling before flowering) alone, but can be partly explained by the accumulated temperature hypothesis (i.e. plants need to achieve a threshold of accumulative temperature before flowering) and/or the overtopping hypothesis (i.e. plants need to reach community canopy layer before flowering). The interspecific difference in the response of reproductive phenology could be attributed to the variation in plant traits including plant height growth, the biomass ratio of root to shoot, and seed mass. These results indicate that a mild winter-biased warming may trigger significant change in plant reproductive phenology in an alpine meadow.

Effect of norfloxacin on algae-cladoceran grazer-larval damselfly food chains: Algal morphology-mediated trophic cascades.

Antibiotic norfloxacin (NOR) has recently been demonstrated to affect the swimming behavior of zooplankton species and phytoplankton-zooplankton interactions, which may further affect trophic cascades. To test this hypothesis, two food chains (Scenedesmus quadricauda-Daphnia magna-larval damselfly and Chlorella vulgaris-D. magna-larval damselfly) were used to examine the effect of NOR concentrations (0, 0.5, 5, and 25 mg L-1) on trophic cascades. In the absence of NOR, larval damselflies reduced grazer density and increased algal density, regardless of algal species. In the presence of NOR, increasing NOR concentration strengthened the positive effect of larval damselflies on the growth of C. vulgaris because larval damselflies suppressed grazer density more efficiently resulting from reduced swimming ability in the grazers. Conversely, increasing NOR concentration reduced the positive effect on the growth of S. quadricauda due to inhibited grazer-induced colony formation in S. quadricauda. Therefore, exposure to NOR altered the direction and strength of trophic cascades and showed species-specific differences, depending on algal morphology-mediated indirect interactions. These findings provide novel insights into how NOR affects aquatic food chains and reveal the importance of algal traits in determining trophic cascades.

Asymmetric interactions of seed-predation network contribute to rare-species advantage.

Although the asymmetry of species linkage within ecological networks is now well recognized, its effect on communities has scarcely been empirically investigated. Based on theory, we predicted that an asymmetric architecture of antagonistic plant-herbivore networks would emerge at the community level and that this asymmetry would negatively affect community-common plants more than rare ones. We tested this prediction by analyzing the architectural properties of an alpine plant and pre-dispersal seed-predator network and its effect on seed loss rate of plants in the Tibetan Plateau. This network showed an asymmetric architecture, where the common plant species (with a larger aboveground biomass per area) were infested by a higher number of predator species. Moreover, they asymmetrically interacted with specialized herbivores, presumably because of greater seed resource abundance. In turn, the asymmetric interactions led to a higher proportion of seed loss in the common plants at the species level. Our results suggest that asymmetric antagonistic networks may improve species coexistence by contributing to a mechanism of rare-species advantage.