Mutualistic Benefit Research Articles

Motivational profile and knowledge creation in eSports: examining the roles of mutualistic co-presence

PurposeResearch on knowledge creation within eSports learning is scarce. This study extends the understanding of competition-oriented collaborative learning in eSports by examining the relationship between the dynamics of knowledge creation modes and the continuum of the motivational profile, along with the moderating effects of mutualistic co-presence therein.Design/methodology/approachParticipants were recruited from the community of massively multiplayer online gamers (MMOGs). Through a quantitative survey, their motivations (i.e. self-extrinsic, self-intrinsic, peer-extrinsic and peer-intrinsic motivations), knowledge creation involvements (i.e. internalization, externalization, combination and socialization) and perception of mutualistic benefit of self and peers were captured for hypothesis testing.FindingsSignificant and positive direct relationships were observed between four motivations and four knowledge creation modes. The mutualistic co-presence positively moderated the positive relationship between the self-extrinsic, peer-extrinsic and peer-intrinsic motivations and socialization. When mutualistic self-benefit were outweighed, peer-extrinsic motivated gamers became less likely to perform internalization, whereas self-extrinsic and peer-extrinsic motivated gamers were less likely to perform combination.Originality/valueThis study is among the first to rationalize the relationship between motivational profile and the dynamics of knowledge creation in eSports learning. The conceptualization of the new construct – mutualistic co-presence – using the ecological concept of symbiosis is uncommon in prior literature. The findings also demonstrate that the four modes of knowledge creation in eSports learning are continuous and interwoven; they can be initiated at any point and do not necessarily occur in a specific sequence.

Increased temperature reduces the positive effect of sulfide-detoxification mutualism on Zostera noltii nutrient uptake and growth

Seagrass meadows form essential ecological components in coastal zones but are rapidly declining worldwide due to anthropogenic impacts, including eutrophication and climate change-related heat waves. An important consequence of increased eutrophication is organic matter input in the sediment, which, together with raised temperatures, stimulates the production of toxic sulfide. Although multiple recent studies have highlighted that seagrass can engage in a mutualistic relationship with lucinid bivalves alleviating sulfide toxicity in the rhizosphere, it remains unclear how this mutualism is affected by temperature and eutrophication. To unravel this relation, we investigated the response of the seagrass Zostera noltii to contrasting sediment organic matter conditions, temperatures and presence/absence of the lucinid clam Loripes orbiculatus in a full-factorial mesocosm experiment. Results demonstrate that temperature increased porewater sulfide and nutrient levels, particularly in treatments with high sediment organic matter content. Interestingly, L. orbiculatus reduced not only sulfide levels, but also porewater nutrients. The removal of sulfide in turn stimulated Z. noltii growth, despite lower nutrient availability. Finally, increased temperature suppressed the mutualistic benefit for Z. noltii as sulfide detoxification became hampered. We conclude that, as eutrophication remains an issue in the coastal zone and temperature extremes will likely become more common in the future, seagrass meadows where lucinids occur may need to increasingly rely on this mutualism. At the same time, however, this interaction will become more strained, with an inherent increasing risk of mutualism breakdown.

Inhibition of a nutritional endosymbiont by glyphosate abolishes mutualistic benefit on cuticle synthesis in Oryzaephilus surinamensis

Glyphosate is widely used as a herbicide, but recent studies begin to reveal its detrimental side effects on animals by targeting the shikimate pathway of associated gut microorganisms. However, its impact on nutritional endosymbionts in insects remains poorly understood. Here, we sequenced the tiny, shikimate pathway encoding symbiont genome of the sawtoothed grain beetle Oryzaephilus surinamensis. Decreased titers of the aromatic amino acid tyrosine in symbiont-depleted beetles underscore the symbionts’ ability to synthesize prephenate as the precursor for host tyrosine synthesis and its importance for cuticle sclerotization and melanization. Glyphosate exposure inhibited symbiont establishment during host development and abolished the mutualistic benefit on cuticle synthesis in adults, which could be partially rescued by dietary tyrosine supplementation. Furthermore, phylogenetic analyses indicate that the shikimate pathways of many nutritional endosymbionts likewise contain a glyphosate sensitive 5-enolpyruvylshikimate-3-phosphate synthase. These findings highlight the importance of symbiont-mediated tyrosine supplementation for cuticle biosynthesis in insects, but also paint an alarming scenario regarding the use of glyphosate in light of recent declines in insect populations.

Host identity and symbiotic association affects the taxonomic and functional diversity of the clownfish-hosting sea anemone microbiome.

All eukaryotic life engages in symbioses with a diverse community of bacteria that are essential for performing basic life functions. In many cases, eukaryotic organisms form additional symbioses with other macroscopic eukaryotes. The tightly linked physical interactions that characterize many macroscopic symbioses create opportunities for microbial transfer, which likely affects the diversity and function of individual microbiomes, and may ultimately lead to microbiome convergence between distantly related taxa. Here, we sequence the microbiomes of five species of clownfish-hosting sea anemones that co-occur on coral reefs in the Maldives. We test the importance of evolutionary history, clownfish symbiont association, and habitat on the taxonomic and predicted functional diversity of the microbiome, and explore signals of microbiome convergence in anemone taxa that have evolved symbioses with clownfishes independently. Our data indicate that host identity and clownfish association shapes the majority of the taxonomic diversity of the clownfish-hosting sea anemone microbiome, and predicted functional microbial diversity analyses demonstrate a convergence among host anemone microbiomes, which reflect increased functional diversity over individuals that do not host clownfishes. Further, we identify upregulated predicted microbial functions that are likely affected by clownfish presence. Taken together our study potentially reveals an even deeper metabolic coupling between clownfishes and their host anemones, and what could be a previously unknown mutualistic benefit to anemones that are symbiotic with clownfishes.

Competition-induced increase of species abundance in mutualistic networks

Nutrients from a flowering plant are shared by its pollinators, giving rise to competition in the latter. Such exploitative competition of pollinators can limit their abundance and affect the global organization of the mutualistic partnership in the plant-pollinator mutualistic community. Here we investigate the effects of the exploitative competition between pollinators on the structure and the species abundance of the mutualistic networks which evolve by changing mutualistic partnership towards higher abundance of species. Simulations show different emergent network characteristics between plants and animals; hub plants connected to many pollinators are very rare while a few super-hub pollinators appear with the exploitative competition included, in contrast to equally many hubs of both types without the exploitative competition. More interestingly, the abundance of plant species increases with increasing the exploitative competition strength. We analyze the inverse of the generalized interaction matrix in the weak-interaction limit to identify the leading structural factors relevant to the species abundance, which are shown to be instrumental in optimizing the network structure to increase the mutualistic benefit and lower the cost of exploitative competition.

Mutualistic benefit in the self-sorted co-aggregates of peri-naphthoindigo and a 4-amino-1,8-naphthalimide derivative.

Photoluminescence enhancement for all the members of a self-sorted co-aggregate was observed for the first time by successfully amalgamating AIEE and social self-sorting. Intermolecular H-bonding and π-π stacking were utilised to prepare several co-aggregates of peri-naphthoindigo (PNI) and a 4-amino-1,8-naphthalimide derivative dye, NH2-NMI. In the heteromeric aggregates, photoluminescence intensities were increased by 28% for the imide and more than 400% for PNI. Due to spectral overlap between the emission of the imide and the absorption of PNI, energy transfer took place from the former to the latter. The heteromeric aggregates are dual emissive and the relative intensities of the emissions can easily be tuned by varying the stoichiometry of the dyes.

Population dynamics of mutualism and intraspecific density dependence: How θ-logistic density dependence affects mutualistic positive feedback

Mutualism describes the biological phenomenon where two or more species are reciprocally beneficial, regardless of their ecological intimacy or evolutionary history. Classic theory shows that mutualistic benefit must be relatively weak, or else it overpowers the stabilizing influence of intraspecific competition and leads to unrealistic, unbounded population growth. Interestingly, the conclusion that strong positive interactions lead to runaway population growth is strongly grounded in the behavior of a single model. This model—the Lotka–Volterra competition model with a sign change to generate mutualism rather than competition between species—assumes logistic growth of each species plus a linear interaction term to represent the mutualism. While it is commonly held that the linear interaction term is to blame for the model's unrealistic behavior, we show here that a linear mutualism added to a θ-logistic model of population growth can prevent unbounded growth. We find that when density dependence is decelerating, the benefit of mutualism at equilibrium is greater than when density dependence is accelerating. Although there is a greater benefit, however, decelerating density dependence tends to destabilize populations whereas accelerating density dependence is always stable. We interpret these findings tentatively, but with promise for the understanding of the population ecology of mutualism by generating several predictions relating growth rates of mutualist populations and the strength of mutualistic interaction.

Evolutionary history shapes patterns of mutualistic benefit in Acacia –rhizobial interactions

The ecological and evolutionary factors that drive the emergence and maintenance of variation in mutualistic benefit (i.e., the benefits provided by one partner to another) in mutualistic symbioses are not well understood. In this study, we evaluated the role that host and symbiont phylogeny might play in determining patterns of mutualistic benefit for interactions among nine species of Acacia and 31 strains of nitrogen-fixing rhizobial bacteria. Using phylogenetic comparative methods we compared patterns of variation in mutualistic benefit (host response to inoculation) to rhizobial phylogenies constructed from housekeeping and symbiosis genes; and a multigene host phylogeny. We found widespread genotype-by-genotype variation in patterns of plant growth. A relatively large component of this variation (21-28%) was strongly influenced by the interacting evolutionary histories of both partners, such that phylogenetically similar host species had similar growth responses when inoculated with phylogenetically similar rhizobia. We also found a relatively large nonphylogenetic effect for the average mutualistic benefit provided by rhizobia to plants, such that phylogenetic relatedness did not predict the overall benefit provided by rhizobia across all hosts. We conclude that phylogenetic relatedness should frequently predict patterns of mutualistic benefit in acacia-rhizobial mutualistic interactions; but that some mutualistic traits also evolve independently of the phylogenies.

Partner diversity and identity impacts on plant productivity in Acacia–rhizobial interactions

Summary Genetic variation for functionally important traits is ubiquitous in communities of nitrogen‐fixing rhizobia, and while some studies have described significant effects of diversity on the functioning of plant‐associated microbial communities, we lack a systematic test of how rhizobial diversity influences plant productivity. The complexity of potential interactions among rhizobia and plants complicates the development of general predictions regarding causal relationships between rhizobial diversity and plant productivity. For example, while rhizobial complementarity may result in positive associations between symbiont diversity and plant productivity, antagonistic competition may reduce rhizobial community function. Using two widespread native Australian Acacia species (A. salicina, A. stenophylla) and experimental rhizobial communities derived from 16 bacterial genotypes naturally associated with these hosts, we examined how the provision of mutualistic benefit varies with rhizobial identity, diversity and phylogenetic relatedness. Analysis of plant performance in relation to rhizobial genotypic richness revealed that the presence of multiple rhizobial genotypes in the rhizosphere was associated with a general decrease in plant productivity compared to growth with single rhizobial genotypes. Importantly, these results appear to be robust in the face of variation in host identity and host diversity (i.e. one or two species mixtures). We also found that rhizobial genotypic identity and host species significantly influenced plant productivity in Acacia–rhizobia interactions, both in single‐ and multistrain inoculations. Synthesis. Together, our data show that multiple rhizobia interacting with a single host species creates opportunities for emergent or higher‐order effects that extend beyond those that could be simply predicted based upon outcomes of pairwise interactions and that increased mutualist diversity does not necessarily translate into positive effects on plant growth.

Ants impact sawfly oviposition on bracken fern in southern California

Although it has been speculated that ant visits to extrafloral nectaries of bracken fern may convey a fitness benefit for the plant, this has never been demonstrated with native herbivores and natural insect densities. We tested the hypothesis that ants attracted to extrafloral nectaries of bracken fern provide a mutualistic benefit by protecting fronds from herbivore damage in a field manipulation experiment in southern California. We examined densities of sawfly eggs and larvae on bracken fronds with and without ant exclusion. Because bracken fern in this region is also impacted by nitrogenous air pollution, we included an N addition treatment. We found that sawfly egg abundance was significantly higher for fern plants when ants were excluded, regardless of N treatment. Ants tended to have higher abundance on fertilized plants, but there was no interaction between N additions and ant exclusion. Bracken fern may derive a fitness benefit from attracting ants during the early phases of plant growth, through decreased herbivore oviposition, rather than through the deterrence of feeding larvae.

Sanctions, Cooperation, and the Stability of Plant-Rhizosphere Mutualisms

There are both costs and benefits for host plants that associate with microbes in the rhizosphere. Typically, an individual plant associates with multiple microbial genotypes varying in mutualistic benefit. This creates a potential tragedy of the commons where less-mutualistic strains potentially share in the collective benefits, while paying less of the costs. Therefore, maintaining cooperation over the course of evolution requires specific mechanisms that reduce the fitness benefits from “cheating.” Sanctions that discriminate among partners based on actual symbiotic performance are a key mechanism in rhizobia and may exist in many rhizosphere mutualisms, including rhizobia, mycorrhizal fungi, root endophytes, and perhaps free-living rhizosphere microbes. Where they exist, sanctions may take different forms depending on the system. Despite sanctions, less-effective symbionts still persist. We suggest this is because of mixed infection at spatial scales that limit the effects of sanctions, variation among plants in the strength of sanctions, and conflicting selection regimes.

Social heterosis and the maintenance of genetic diversity at the genome level

AbstractSocial heterosis is when individuals in groups or neighbourhoods receive a mutualistic benefit from across‐individual genetic diversity. Although it can be a viable evolutionary mechanism to maintain allelic diversity at a given locus, its efficacy at maintaining genome‐wide diversity is in question when multiple loci are being simultaneously selected. Therefore, we modelled social heterosis in a population of haploid genomes of two‐ or three‐linked loci. With such linkages, social heterosis decreases gametic diversity, but maintains allelic diversity. Genomes tend to survive as complimentary pairs, with alternate alleles at each locus (e.g. the pair AbC and aBc). The outcomes of selection appear similar to fitness epistasis but are novel in the sense that phenotypic interactions occur across rather than within individuals. The model’s results strongly suggest that strong linkage across gene loci actually increases the probability that social heterosis maintains significant genetic diversity at the level of the genome.

Neotyphodium infection and hybridisation as a function of environmental variation

Neotyphodium is an asexual, vertically transmitted, obligate fungal endosymbiont infecting cool-season grasses such as Arizona fescue. The relationship between Neotyphodium and several native grass hosts ranges from antagonistic to mutualistic. One theory that may explain how Neotyphodium infection is maintained despite inconsistent mutualistic benefit to the host is the bounded hybrid superiority hypothesis. This hypothesis argues that hybrids are more fit than non-hybrids in response to some environmental stresses. Neotyphodium infects hosts in both hybrid and non-hybrid forms. We tested the possibility of hybrid superiority in depauperate habitats (low soil water and nitrate) by quantifying the types and frequency of host infections (uninfected, hybrid-infected and non-hybrid-infected), and the quality of resources available between three host populations. A second theory, the geographic mosaic theory of coevolution, may also explain different symbiotic outcomes at the population level in response to variation in abiotic and biotic population characters. We provide cursory support for both hypotheses. Keywords: geographic mosaic theory of coevolution, hybrid, Festuca, Neotyphodium, symbiosis, mutualism, bounded hybrid superiority

Atypical morphology of dark septate fungal root endophytes of Bouteloua in arid southwestern USA rangelands.

Native grasses of semi-arid rangelands of the southwestern USA are more extensively colonized by dark septate endophytes (DSE) than by traditional mycorrhizal fungi. Roots of dominant grasses ( Bouteloua sp.) native to arid southwestern USA rangelands were prepared and stained using stains specific for fungi (trypan blue) and for lipids (sudan IV). This revealed extensive internal colonization of physiologically active roots by atypical fungal structures that appear to function as protoplasts, without a distinguishable wall or with very thin hyaline walls that escape detection by methods staining specifically for fungal chitin. These structures were presumed to be active fungal stages that progressed to form stained or melanized septate hyphae and microsclerotia characteristic of DSE fungi within dormant roots. The most conspicuous characteristic of these fungi were the unique associations that formed within sieve elements and the accumulation of massive quantities of lipids. This interface suggests a biologically significant location for carbon transfer between the plant and fungus. The continuous intimate association with all sieve elements, cortical and epidermal cells as well as external extension on the root surface and into the soil indicates that they are systemic and considerably more prevalent than previously thought. A fungal network associated with a mucilaginous complex observed on the root surface and its potential role in root function in dry soil is discussed. It is suggested that those fungi that non-pathogenically and totally colonize plant cells be classed as systemic endophytic fungi (SEF). This would refine the broad designation of DSE fungi. The potential mutualistic benefit of SEF for native plants in arid ecosystems based on the extent of lipid accumulation and its apparent distribution is discussed.

Negative feedback within a mutualism: host-specific growth of mycorrhizal fungi reduces plant benefit.

A basic tenet of ecology is that negative feedback on abundance plays an important part in the coexistence of species within guilds. Mutualistic interactions generate positive feedbacks on abundance and therefore are not thought to contribute to the maintenance of diversity. Here, I report evidence of negative feedback on plant growth through changes in the composition of their mutualistic fungal symbionts, arbuscular mycorrhizal (AM) fungi. Negative feedback results from asymmetries in the delivery of benefit between plant and AM fungal species in which the AM fungus that grows best with the plant Plantago lanceolata is a poor growth promoter for Plantago. Growth of Plantago is, instead, best promoted by the AM fungal species that accumulate with a second plant species, Panicum sphaerocarpon. The resulting community dynamic leads to a decline in mutualistic benefit received by Plantago, and can contribute to the coexistence of these two competing plant species.

Queen condition and alate density affect pleometrosis in the antLasius pallitarsis

Ant queens often cooperate in starting colonies (pleometrosis), but not all foundresses are likely to achieve equal reproductive success. Therefore, joining decisions may be influenced by queens' perceptions of a partner's likelihood to be of mutualistic benefit or to be a successful competitor in eventually controlling reproduction. Large queen size (as measured by weight) was assumed to be a desired characteristic in a mutualistic partner, but to be avoided in a potential competitor. With respect to this variable,Lasius pallitarsis queens appeared to join others in a manner consistent with increasing their competitive advantage. When given a choice between joining another queen or nesting alone, only queens with a large weight advantage were significantly likely to join. When given a choice between joining either a light or a heavy queen, queens of all weights preferentially joined the lighter resident. Moreover, when queen condition was improved by feeding, changes in joining behavior were consistent with predictions of improved competitive ability. Finally, lighter queens were more likely to leave nest sites when joined by others. However, queens significantly aggregated when in high densities, which may be consistent with gaining mutualistic benefits. Pleometrosis appears to have an evolutionary dynamic between mutualistic group benefits and individual competition to monopolize those benefits.

On the structure and stability of mutualistic systems: Analysis of predator-prey and competition models as modified by the action of a slow-growing mutualist

Two basic models of mutualism are presented in which interactions among three species lead to mutualism between two of them. The models represent 2-species predator-prey or competition systems in which a third species acts as a mutualist with either the predator, the prey, or one of the competitors. The models include the assumptions that there is a cost of associating with the mutualist and that the mutualist population grows much more slowly than the other two populations. Special cases of these two models correspond to six qualitatively different types of mutualistic benefit, all of which are known to occur in nature: deterring predation, increasing prey availability, feeding on (or competing with) a predator, increasing competitive interactions, decreasing competitive interactions, and feeding on (or competing with) a competitor. These models and their special cases are subjected to a local stability analysis. The results show that mutualism based upon deterring predation, competing with a predator, or decreasing competitive interactions enhances local stability, while mutualism based upon increasing prey availability or increasing competitive interactions reduces local stability. These results clearly reject the idea that mutualism is an inherently unstable process, and reinforces the idea that each different kind of mutualism will have to be considered separately. Compared to 2-species models of mutualism, the 3-species models provide a more realistic representation of the structure of many mutualistic systems, the mechanisms by which one species benefits another, and the regulation of the interaction.