Effects of Rice-duck Mutualism on Diseases Insect Pests and Weeds and Economic Benefits

[Objective] Study on the effects of rice-duck mutualism on weeds and insects pests and economic benefits of paddy field. [Method] Comparison of the incidence of weeds, sheath blight and insects pest under rice-duck mutualism, conventional cultivation and control treatment, the yield and economic benefits were analyzed under the 3 treatments. [Result] Average occurrence of weeds in rice-duck mutualism group decreased by 2.33 and 52.0g ind/m^2 compared with that in conventional cultivation and control treatment ; the control rate of mutualism was up to 75% against rice hopper, but just between 25% -60% against rice leaf roller and Chilo suppressalis. The rates of diseased plant and diseased bell against rice sheath blight were higher and disease indices were lower compared with control group. The yield of mutualism group was identical with conventional cultivation, Which was greatly higher than that of control group. The results suggested an higher economic benefits and lower cost benefit ratio for rice-duck mutualism treatment. [Conclusion] Rice-duck mutualism gives birth to a positive effect to control the diseases, insect pests and weeds, as well as to economic benefits, providing basis on extension of rice-duck mutualism system.

Seed and Wasp Production in the Mutualism of Figs and Fig Wasps

Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.

A Study on the Rebirth of Buck Based on the Repetitive Breakage and Es⁃tablishment of Mutualism

In the Book The Call of the Wild,Buck experiences numerous ups and downs in his life.He changes from a tamed dog to a most powerful and persevered leader of wolves in the primitive forest.He finally answers the call of his ancestor and the call of nature,returning to the place where he is destined to be.The naturalism as well as symbolism is heated discussed in this book to date.However,the study on the rebirth of Buck from the perspective of mutualism still remains a relative blank area.This article further analyzes the rebirth with the analyzing method of mutualism and the concrete context.The repetitive breakage and establish⁃ment of various mutual relationships for Buck gradually reshape some of his features and wakes up something inherited,deep root⁃ed but once hidden in his soul.These features eventually pushes him to reach the peak of his life—the life he is meant to be and in which he becomes a true warrior.

Synchronization in a Mutualism Ecosystem Induced by Noise Correlation

Understanding the cause of the synchronization of population evolution is an important issue for ecologicalimprovement.Here we present a Lotka-Volterra-type model driven by two correlated environmental noises and show,via theoretical analysis and direct simulation,that noise correlation can induce a synchronization of the mutualists.Thetime series of mutual species exhibit a chaotic-like fluctuation,which is independent of the noise correlation,however,the chaotic fluctuation of mutual species ratio decreases with the noise correlation.A quantitative parameter defined forcharacterizing chaotic fluctuation provides a good approach to measure when the complete synchronization happens.

A Theory of Ratio Selection—Lattice Model for Obligate Mutualism

Mutualisms are cooperative interactions between members of different species. We focus on obligate mutualism, where each species cannot survive without the other. From a theoretical aspect, obligate mutualism is similar to the relationship between male and female. Empirical data indicate a sex-ratio selection: male and female have a specific ratio in their population sizes. In the present paper, we apply lattice model to obligate mutualism between two species, and present a theory of “ratio selection” which is a generalization of sex-ratio selection. Computer simulations are carried out by two methods: local and global interactions. In the former, interactions occur between neighbouring cells, while in the latter they occur between any pair of cells. Simulations in both interactions show the so-called Allee effect: both species can survive, when both densities are large in some extent. However, we find a large difference between local and global simulations. In the case of local interaction, restriction for survival is found to be extremely severe compared to global interaction. Both species require a proper ratio for their sustainability. This result leads to the theory of ratio selection: when interaction occurs locally, the ratio of both species is uniquely determined. We discuss that the ratio selection explains not only the evolution of endosymbionts from free-living ancestors but also the evolution from endosymbionts to organelles.

Masting promotes transformation from predation to mutualism in an oak-weevil-rodent system

The significance of ecological non-monotonicity(a function whose first derivative changes signs)in shaping the structure and functions of the ecosystem has recently been recognized,but such studies involving high-order interactions are rare.Here,we have proposed a threetrophic conceptual diagram on interactions among trees,rodents,and insects in mast and non-mast years and tested the hypothesis that oak(Quercus wutaishanica)masting could result in increased mutualism and less predation in an oak-weevil-rodent system in a warm temperate forest of China.Our 14-year dataset revealed that mast years coincided with a relatively low rodent abundance but a high weevil abundance.Masting not only benefited seedling recruitment of oaks through increased dispersal by rodents but also a decrease in predation by rodents and weevils,as well as an increase in the overwintering survival of rodents.Masting appeared to have increased weevil survival by reducing predation of infested acorns by rodents.These results suggest that masting benefits all participants in the plant-insect-rodent system by increasing mutualism and reducing predation behavior(i.e.,a non-monotonic function).Our study highlights the significance of masting in maintaining the diversity and function of the forest ecosystem by facilitating the transformation from predation to mutualism among trophic species.

Mutualism between antagonists:its ecological and evolutionary implications

Mutualism or antagonism between species is often investigated within the framework of monotonic interactions of either mutualism or antagonism,but studies on transition from mutualism to antagonism(within the context of nonmonotonic interactions)have been largely ignored.In this paper,through a brief review and synthesis,we highlighted the role of mutualism between antagonists in regulating the ecological and evolutionary processes,as well as maintaining the stability and complexity of ecosystems.Mutualism between antagonistic species represents the density-dependent transition between mutualism and antagonism,which is beneficial to species coexistence and stability of complex ecosystems;thus,it should be favored by natural selection.Species may face selection of conflicting pressure on functional traits in co-balancing mutualism and antagonism,which may result in evolution of the dual character of species with moderate mutualistic or antagonistic traits.Coevolution and co-balance of these traits are driving forces in shaping mutualism-antagonism systems.Rewards for mutualists,punishment for exploiters,and competition of meta-communities are essential in stabilizing mutualism between antagonists.We appeal for more studies on mutualism between antagonists and its ecological and evolutionary implications by expanding the conventional ecological studies from monotonic to nonmonotonic regimes.

Seed traits and taxonomic relationships determine the occurrence of mutualisms versus seed predation in a tropical forest rodent and seed dispersal system

Although many studies have been carried out on plant-animal mutualistic assemblages,the roles of function­al traits and taxonomy in determining both whether interactions involve mutualisms or predation and the struc­ture of such assemblages are unclear.We used semi-natural enclosures to quantitatively assess the interaction strengths between seeds of 8 sympatric tree species and 4 rodent species in a tropical forest in Xishuangban­na,Yunnan,Southwest China.We found 2 clusters of species in the seed-rodent network represented by 2 gen­era in the Fagaceae(Castanopsis,Lithocarpus).Compared to seeds of 3 Castanopsis species,seeds with heavy weight,hard coat or caloric content(including 3 Lithocarpus species)were eaten less and more frequently hoarded by rodents.In turn,hoarded seeds showed less predation and more mutualism with rodents.Our results suggest that seed traits significantly affected the hoarding behavior of rodents,and,consequently,the occurrence of mutualisms and predation as well as assemblage structure in the plant-animal seed dispersal system.Taxo­nomically-related species with similar seed traits as functional groups belong to the same substructures in the assemblage.Our results indicate that both seed traits and taxonomic relationships may simplify thinking about seed dispersal systems by helping to elucidate whether interactions are likely to be dominated by predation or mutualism.

Rodent abundance triggered switch between the relative mutualism and predation in a rodent-seed system of the subtropical island forest

Density-dependent non-monotonic species interactions are important in maintaining ecosystem stability and function,but empirical evidences are still rare.Rodents,as both seed dispersers and seed predators,have dual effects on plant regeneration and may result in non-monotonic rodent-plant interactions.According to the non-monotonic models,the relative positive or negative effects of rodents on seedling establishment can be measured based on the positive or negative association of seedling recruitment rate and rodent abundance.In this study,we investigated the fates of acorns of Quercus serrata by tracking tagged seeds on 21 fragmented subtropical islands in the Thousand Island Lake,China.We found that the proportion of germinated seeds of all released seeds showed a dome-shaped association with rodent abundance per seed.The proportion of removed seeds and cached seeds showed a saturated-and a weak dome-shaped association with rodent abundance per seed,respectively.Our results demonstrated a clear empirical evidence that rodent abundance per seed triggered a switch between the relative mutualism and predation in a rodent-seed system.Our study implied that the observed non-monotonic interactions between plants and animals may play a significant role in maintaining biodiversity and ecosystem function.We appeal for more investigations of the complex non-monotonic interactions in various ecosystems.

Survival analysis of an impulsive stochastic facultative mutualism system with saturation effect

A system of impulsive stochastic differential equations is proposed as a two-species facultative mutualism model subject to impulsive and two coupling noise source perturbations,in which the saturation effect is taken into account.A set of sufficient criteria for extinction(exponential extinction and extinction)and permanence(permanence in time average and stochastic permanence)of the system are established.Extensive simulation figures are demonstrated to support the theoretical findings.Meanwhile,we look at the effects of coupling white noises,impulses,intrinsic growth rates,intra-specific competition rates and inter-specific mutualism rates on the survival of populations.

Seed dispersal by hornets:An unusual insect-plant mutualism

Vespicochory, seed dispersal by hornets, is a rare seed dispersal mechanism in angiosperms and, to date, there are few records of this phenomenon.Through field investigations and behavioral assays conducted in four populations of Stemona tuberosa from 2011–2016, we demonstrate that hornets are the primary seed dispersers of S. tuberosa and play an important role in "long-distance" seed dispersal in this species. Furthermore, some ant species act as secondary dispersers and may transport the seeds to safe sites.Hornets and ants provide complementary seed dispersal at different spatial scales. This unique example of insect-plant mutualism may be an underestimated but important strategy to ensure "long-distance" seed dispersal in other myrmecochorous plants.

Analysis of a mutualism model with time-related coefficients in a stochastic environment

In this paper,a mutualism model with stochastic perturbations is considered and some of its coefficients are related to time.Under some assumptions,we make efforts to prove the existence and uniqueness of a positive solution,and the asymptotic behavior to the problem is discussed.Furthermore,we also prove the properties of stochtistic boundedness,uniform continuity and stochastic permanence of this system.At last,some numerical simulations are introduced to illustrate our main results.

The Potential for Genotype-by-Environment Interactions to Maintain Genetic Variation in a Model Legume–Rhizobia Mutualism

The maintenance of genetic variation in mutualism-related traits is key for understanding mutualism evolution,yet the mechanisms maintaining variation remain unclear.We asked whether genotype-byenvironment(G3E)interaction is a potential mechanism maintaining variation in the model legume–rhizobia system,Medicago truncatula–Ensifer meliloti.We planted 50 legume genotypes in a greenhouse under ambient light and shade to reflect reduced carbon availability for plants.We found an expected reduction under shaded conditions for plant performance traits,such as leaf number,aboveground and belowground biomass,and a mutualism-related trait,nodule number.We also found G3E for nodule number,with83%of this interaction due to shifts in genotype fitness rank order across light environments,coupled with strong positive directional selection on nodule number regardless of light environment.Our results suggest that G3E can maintain genetic variation in a mutualism-related trait that is under consistent positive directional selection across light environments.

Spatial heterogeneity and host repression in fig-fig wasp mutualism

It is generally believed that physical heterogeneity in common resource or evolutionary restraint can sufficiently prevent direct conflict between host and symbionts in mutualism systems. Our data on fig/fig wasp reciprocal mutualism(Ficus racemosa), however, show that structural barriers of female flowers or genetic constraints of pollinators previously hypothesized exist, but cannot sufficiently maintain the mutualism stability. The results show that a positive relationship between seed and wasp production could be maintained in warm season, which might be because of density dependence restraint among foundresses and their low oviposition and pollination efficiency, keeping common resource(female flowers) utilization unsaturated. Whilst, a negative correlation between wasp offspring and viable seed production was also observed in cold season, which might be that the increased oviposition and pollination efficiency maximized the common resource utilization. The fitness trade-off between fig and pollinator wasps is greatly affected by environmental or ecological variations. The local stability might result from temporal low exploitation efficiency of pollinators together with interference competition among pollinators. We suggest that host repression through the active regulation of bract closure, which can create interference competition among the foundresses and prevent extra more foundresses sequential entry in fruit cavities, would help the figs avoiding the cost of over-exploitation. This essentially takes the same role as sanctioning of cheating or competitive behaviors.

GLOBAL ASYMPTOTICAL STABILITY OF AN OBLIGATE LOTKA-VOLTERRA MUTUALISM MODEL

By constructing a suitable Lyapunov function,sufficient conditions which ensure the global asymptotical stability of the positive equilibrium and boundary equilibrium of an obligate Lotka-Volterra mutualism model are obtained,respectively.It is shown that the conditions which ensure the local stability of the nonnegative equilibria is enough to ensure their global asymptotical stability.Our result supplements and complements some known result.

Tuning the diffusion constant to optimize the readout of positional information of spatial concentration patterns

Positional information encoded in spatial concentration patterns is crucial for the development of multicellular organisms.However,it is still unclear how such information is affected by the physically dissipative diffusion process.Here we study one-dimensional patterning systems with analytical derivation and numerical simulations.We find that the diffusion constant of the patterning molecules exhibits a nonmonotonic effect on the readout of the positional information from the concentration patterns.Specifically,there exists an optimal diffusion constant that maximizes the positional information.Moreover,we find that the energy dissipation due to the physical diffusion imposes a fundamental upper limit on the positional information.

Mutual Information Maximization via Joint Power Allocation in Integrated Sensing and Communications System

In this paper, we focus on the power allocation of Integrated Sensing and Communication(ISAC) with orthogonal frequency division multiplexing(OFDM) waveform. In order to improve the spectrum utilization efficiency in ISAC, we propose a design scheme based on spectrum sharing, that is,to maximize the mutual information(MI) of radar sensing while ensuring certain communication rate and transmission power constraints. In the proposed scheme, three cases are considered for the scattering off the target due to the communication signals,as negligible signal, beneficial signal, and interference signal to radar sensing, respectively, thus requiring three power allocation schemes. However,the corresponding power allocation schemes are nonconvex and their closed-form solutions are unavailable as a consequence. Motivated by this, alternating optimization(AO), sequence convex programming(SCP) and Lagrange multiplier are individually combined for three suboptimal solutions corresponding with three power allocation schemes. By combining the three algorithms, we transform the non-convex problem which is difficult to deal with into a convex problem which is easy to solve and obtain the suboptimal solution of the corresponding optimization problem. Numerical results show that, compared with the allocation results of the existing algorithms, the proposed joint design algorithm significantly improves the radar performance.

New construction of mutually unbiased bases for odd-dimensional state space

We study the construction of mutually unbiased bases in Hilbert space for composite dimensions d which are not prime powers.We explore the results for composite dimensions which are true for prime power dimensions.We then provide a method for selecting mutually unbiased vectors from the eigenvectors of generalized Pauli matrices to construct mutually unbiased bases.In particular,we present four mutually unbiased bases in C^(15).

Quantized Decoders that Maximize Mutual Information for Polar Codes

In this paper,we innovatively associate the mutual information with the frame error rate(FER)performance and propose novel quantized decoders for polar codes.Based on the optimal quantizer of binary-input discrete memoryless channels(BDMCs),the proposed decoders quantize the virtual subchannels of polar codes to maximize mutual information(MMI)between source bits and quantized symbols.The nested structure of polar codes ensures that the MMI quantization can be implemented stage by stage.Simulation results show that the proposed MMI decoders with 4 quantization bits outperform the existing nonuniform quantized decoders that minimize mean-squared error(MMSE)with 4 quantization bits,and yield even better performance than uniform MMI quantized decoders with 5 quantization bits.Furthermore,the proposed 5-bit quantized MMI decoders approach the floating-point decoders with negligible performance loss.

Analytical modeling and approaches of multihelix cables incorporating with interwire mutual contacts

This study aims to develop an analytical model based on the curve beam theory to capture the mechanical response of a multihelix cable considering the internal contact displacements.Accordingly,a double-helix cable subjected to axial tension and torsion is analyzed,and both the line and point contacts between the neighboring wires and strands are considered via an equivalent homogenized approach.Then,the proposed theoretical model is extended to a hierarchical multihelix cable with mutual contact displacements by constructing a recursive relationship between the high-and low-level multihelix structures.The global tensile stiffness and torsional stiffness of the double-helix cable are successfully evaluated.The results are validated by a finite element(FE)model,and are found to be consistent with the findings of previous studies.It is shown that the contact deformations in multihelix cables significantly affect their equivalent mechanical stiffness,and the contact displacements are remarkably enhanced as the helix angles increase.This study provides insights into the interwire/interstrand mutual contact effects on global and local responses.