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Borgström, Pernilla, Joachim Strengbom, Maria Viketoft, and Riccardo Bommarco. "Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect." PeerJ 4 (April 4, 2016): e1867. http://dx.doi.org/10.7717/peerj.1867.
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Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition:Dactylis glomerataL., which is competitively favoured by nitrogen addition, andFestuca rubraL., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage ofD. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage ofF. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability ofF. rubra, and a 23% increase in that ofD. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory.D. glomerataremained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion ofF. rubra. Belowground herbivory appeared to mitigate the influence of aboveground herbivory, and this mechanism may play a role for plant species coexistence.
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Collins, B., and G. R. Wein. "Competition between native and immigrant Polygonum congeners." Canadian Journal of Botany 71, no. 7 (1993): 939–45. http://dx.doi.org/10.1139/b93-105.
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Coexistence of annual herbs Polygonum punctatum, a native, and Polygonum caespitosum, an immigrant, may result from (i) niche differentiation that reduces or avoids competition, (ii) competitive equivalence for shared resources, or (iii) interaction between a strong competitor and a species that tolerates competition. We investigated competitive interactions between the Polygonum congeners in a greenhouse experiment using plants grown from seed to seed set. Thinning profiles of monocultures were density dependent but did not differ between the species in monocultures. Biomass allocation to root, shoot, and racemes was not influenced by competition from conspecifics or congeners. Mature plant height and raceme production of both species were negatively affected by congener density; however, the species were not competitively equivalent. Polygonum caespitosum was suppressed into the shorter heights in mixture pots but produced more racemes at all but the greatest congener densities. Key words: competition, coexistence, annual herbs, immigrant.
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Neill, Paula E., Nicolás Rozbaczylo, Cristóbal Villaseñor-Parada, Garen Guzmán-Rendón, Sandra Sampértegui, and Cristián E. Hernández. "Patterns of association of native and exotic boring polychaetes on the southeastern Pacific coast of Chile: the combined importance of negative, positive and random interactions." PeerJ 8 (April 24, 2020): e8560. http://dx.doi.org/10.7717/peerj.8560.
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Background Studies of biological invasions focus on negative interactions between exotic and native biotas, emphasizing niche overlap between species and competitive exclusion. However, the effects of positive interactions and coexistence are poorly known. In this study we evaluate the importance of positive, negative, or random species associations in explaining the coexistence of native and exotic boring polychaetes inhabiting invertebrate hosts, on the southeastern Pacific coast of Chile. We assess three hypotheses to explain the observed patterns: positive species interactions, weak competitive interactions, and competitive intransitivity. Methodology To assess the potential effect of competition between native and exotic polychaetes we analyzed patterns of co-occurrence of species pairs in northern and southern regions, using the metric of the probabilistic model. Since biotic interactions can affect not only native species, we also evaluated correlations between native and exotic polychaete abundance, using reduced major axis regression linear models. To assess the transitivity of competitive hierarchies we used metrics and analytical methods based on abundance matrices to estimate species competition and patch transition matrices. Results On average 50% of the species pairs presented significant weak negative associations, all associated with the exotic species Polydora rickettsi; the remaining 50% had random associations, and none showed positive associations. However, the relationship of abundance between native and exotic boring polychates supports a tendency towards coexistence. At local and regional scales, we observed the presence of a transitive network competition structure, where the exotic boring polychaete, P. rickettsi was generally the dominant species. Conclusions Our results support that native and exotic boring polychaete species coexist through weak competitive interactions. Nevertheless, the large number of random interactions observed indicates that species coexistence can be accounted for by stochastic processes, as proposed by neutral theory. Coexistence may be a frequent result of interactions between native and exotic species, although less apparent than competitive exclusion. Thus, the probabilistic point-of-view used here provides a statistical tool for evaluating coexistence as a result of exotic and native species’ interactions, an idea which has been proposed in invasion ecology, but largely lacks empirical support and methodologies for detecting underlying mechanisms. Finally, we found evidence that P. rickettsi is a successful invader by being competitively dominant, but not excluding other species.
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Verhoeven, Michael R., Wesley J. Glisson, and Daniel J. Larkin. "Niche Models Differentiate Potential Impacts of Two Aquatic Invasive Plant Species on Native Macrophytes." Diversity 12, no. 4 (2020): 162. http://dx.doi.org/10.3390/d12040162.
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Potamogeton crispus (curlyleaf pondweed) and Myriophyllum spicatum (Eurasian watermilfoil) are widely thought to competitively displace native macrophytes in North America. However, their perceived competitive superiority has not been comprehensively evaluated. Coexistence theory suggests that invader displacement of native species through competitive exclusion is most likely where high niche overlap results in competition for limiting resources. Thus, evaluation of niche similarity can serve as a starting point for predicting the likelihood of invaders having direct competitive impacts on resident species. Across two environmental gradients structuring macrophyte communities—water depth and light availability—both P. crispus and M. spicatum are thought to occupy broad niches. For a third dimension, phenology, the annual growth cycle of M. spicatum is typical of other species, whereas the winter-ephemeral phenology of P. crispus may impart greater niche differentiation and thus lower risk of native species being competitively excluded. Using an unprecedented dataset comprising 3404 plant surveys from Minnesota collected using a common protocol, we modeled niches of 34 species using a probabilistic niche framework. Across each niche dimension, P. crispus had lower overlap with native species than did M. spicatum; this was driven in particular by its distinct phenology. These results suggest that patterns of dominance seen in P. crispus and M. spicatum have likely arisen through different mechanisms, and that direct competition with native species is less likely for P. crispus than M. spicatum. This research highlights the utility of fine-scale, abundance-based niche models for predicting invader impacts.
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Moral, Roger del. "Competitive effects on the structure of subalpine meadow communities." Canadian Journal of Botany 63, no. 8 (1985): 1444–52. http://dx.doi.org/10.1139/b85-200.
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The effects of competition in a subalpine meadow environment were investigated by comparing within-habitat distributions and species overlap in four communities. Based on experimental studies of these communities, it was hypothesized that structural patterns should be affected by productivity changes. It was determined that such changes are nonlinear and that the most stressed and the most competitive communities share many similar properties. Among closed, relatively productive communities, mean niche width, niche width of competitively inferior species, total overlap, and overlap among weak competitors all declined with increased competitive intensity. In contrast, niche width of dominant species changed little and overlap among space-holding species increased. The use of comparative pattern measures can complement and enhance the analysis of community structure and dynamics based on experimental methods.
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Sánchez-García, Daniel, Xim Cerdá, and Elena Angulo. "Temperature or competition: Which has more influence on Mediterranean ant communities?" PLOS ONE 17, no. 4 (2022): e0267547. http://dx.doi.org/10.1371/journal.pone.0267547.
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Temperature and competition are two of the main factors determining ant community assemblages. Temperature may allow species to forage more or less efficiently throughout the day (in accordance with the maximum activity temperature of each species). Competition can be observed and quantified from species replacements occurring during resource exploitation. We studied the interspecific competitive interactions of ant communities from the Doñana Biological Reserve (southern Spain). Ants were sampled from pitfall traps and baits in three habitats with contrasted vegetation physiognomy (savin forest, pine forest, and dry scrubland). We measured the temperature during the competitive interactions between species and created a thermal competition index (TCI) to assess the relative contribution of temperature and numerical dominance to the competitive outcomes. Temperature had unequal effects on ant activity in each type of habitat, and modulated competitive interactions. The TCI showed that a species’ success during pair interactions (replacements at baits) was driven by the proportion of workers between the two competing species and by the species-specific effect of temperature (how advantageous the temperature change is for each species during bait replacement). During competitive interactions, the effect of temperature (higher values of TCI) and numeric supremacy (higher worker proportion) gave higher success probabilities. Interspecific competitive relationships in these Mediterranean ant communities are habitat dependent and greatly influenced by temperature.
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Vera, María Carmen, Marcos Marvá, Víctor José García-Garrido, and René Escalante. "The Beddington–DeAngelis Competitive Response: Intra-Species Interference Enhances Coexistence in Species Competition." Mathematics 12, no. 4 (2024): 562. http://dx.doi.org/10.3390/math12040562.
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Species coexistence is a major issue in ecology. We disentangled the role of individual interference when competing in the classical interference competition model. For the first time, we considered simultaneously intra- and inter-species interference by introducing the Beddington–DeAngelis competitive response into the classical competition model. We found a trade-off between intra- and inter-species interference that refines in a sense the well-known balance of intra- and inter-species competition coefficients. As a result, we found that (i) global coexistence is possible for a larger range of values of the inter-/intra-species competition coefficients and contributes to explaining the high prevalence of species coexistence in nature. This feature is exclusively due to intra-species interference. (ii) We found multi-stability scenarios previously described in the literature that can be reinterpreted in terms of individuals interference.
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Dungan, Michael L. "Competition and the morphology, ecology, and evolution of acorn barnacles: an experimental test." Paleobiology 11, no. 2 (1985): 165–73. http://dx.doi.org/10.1017/s0094837300011489.
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Recent ideas about the role of competition in the ecology and evolution of acorn barnacles are based partly on relationships between morphology and the outcome of competition for space. One hypothesis is that present distributions and patterns of evolutionary diversification and decline among acorn barnacles reflect the competitive exclusion and replacement of solid-walled forms by those with tubiferous skeletal structure. An alternate view is that large barnacles generally outcompete smaller ones, independent of differences in skeletal structure, with predation and disturbance favoring the ecological and evolutionary success of small barnacles. Field experiments and observations in the Gulf of California suggested that the small, solid-walled species, Chthamalus anisopoma, competitively exlcudes the larger, tubiferous Tetraclita stalactifera confinis on the lower part of the shore. Greater tolerance to aerial exposure appears to allow Tetraclita to occupy a high intertidal refuge above Chthamalus. A common denominator among several cases of competitive exclusion in acorn barnacles is the greater settlement density of the competitive dominant, not its morphology. Morphological considerations alone are insufficient to predict or explain the outcome of competition between barnacle species.
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Larocque, Guy R., Nancy Luckai, Shailendra N. Adhikary, Arthur Groot, F. Wayne Bell, and Mahadev Sharma. "Competition theory — science and application in mixed forest stands: review of experimental and modelling methods and suggestions for future research." Environmental Reviews 21, no. 2 (2013): 71–84. http://dx.doi.org/10.1139/er-2012-0033.
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Competition in forest stands has long been of interest to researchers. However, much of the knowledge originates from empirical studies that examined the effects of competition. For instance, many studies were focused on the effects of the presence of herbaceous species on the development of tree seedlings or the decrease in individual tree growth with increases in stand density. Several models that incorporate competitive effects have been developed to predict tree and stand growth, but with simplified representations of competitive interactions. While these studies provided guidance useful for forest management, they contributed only partially to furthering our understanding of competitive mechanisms. Also, most competition studies were conducted in single-species stands. As competitive interactions occurring in mixed stands are characterized by a higher degree of complexity than those in single-species stands, a better understanding of these mechanisms can contribute to developing optimal management scenarios. The dynamics of forest stands with at least two species may be affected not only by competition, but also by facilitation or complementarity mechanisms. Thus, knowledge of the mechanisms may provide insight into the relative importance of intra- versus inter-specific competition and whether competition is symmetric or asymmetric. Special attention to the implementation of field experimental designs is warranted for mixed stands. While traditional spacing trials are appropriate for single-species stands, the examination of competitive interactions in mixed stands requires more complex experimental designs to examine the relative importance of species combinations. Forest productivity models allow resource managers to test different management scenarios, but again most of these models were developed for single-species stands. As competitive interactions are more complex in mixed stands, models developed to predict their dynamics will need to include more mechanistic representations of competition.
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Hasibuan, Arjun, Asep Kuswandi Supriatna, and Ema Carnia. "Mathematical Model of Iteroparous and Semelparous Species Interaction." CAUCHY: Jurnal Matematika Murni dan Aplikasi 7, no. 3 (2022): 445–63. http://dx.doi.org/10.18860/ca.v7i3.16447.
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A species can be categorized based on its reproductive strategy, including semelparous and iteroparous. Semelparous species is a species that reproduces only once in its lifetime shortly before dying, while iteroparous species is a species that reproduces in its lifetime more than once. In this paper, we examine multispecies growth dynamics involving both species categories focusing on one semelparous species and one iteroparous species influenced by density-dependent also harvesting in which there are two age classes each. We divided the study into two models comprising competitive and non-competitive models of both species. Competition in both species can consist of competition within the same species (intraspecific competition) and competition between different species (interspecific competition). Our results show that the level of competition both intraspecific and interspecific affects the co-existence equilibrium point and the local stability of the co-existence equilibrium point.
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Sheppard, Christine S., and Marco R. Brendel. "Competitive ability of native and alien plants: effects of residence time and invasion status." NeoBiota 65 (May 25, 2021): 47–69. http://dx.doi.org/10.3897/neobiota.65.63179.
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Competition is commonly thought to underlie the impact of plant invasions. However, competitive effects of aliens and competitive response of natives may also change over time. Indeed, as with time, the novelty of an invader decreases, the accumulated eco-evolutionary experience of resident species may eventually limit invasion success. We aimed to gain insights on whether directional changes in biotic interactions over time or more general differences between natives and aliens, for instance, resulting from an introduction bias, are relevant in determining competitive ability. We conducted a pairwise competition experiment in a target-neighbour design, using 47 Asteraceae species with residence times between 8 years-12,000 years in Germany. We first tested whether there are differences in performance in intraspecific competition amongst invasion status groups, that is casual and established neophytes, archaeophytes or native species. We then evaluated whether competitive response and effects depend on residence time or invasion status. Lastly, we assessed whether competitive effects influence range sizes. We found only limited evidence that native target species tolerate neighbours with longer potential co-existence times better, whereas differences in competitive ability were mostly better explained by invasion status than residence time. Although casual neophytes produced most biomass in intraspecific competition, they had the weakest per-capita competitive effects on natives. Notably, we did not find differences between established neophytes and natives, both of which ranked highest in interspecific competitive ability. This lack of differences might be explained by a biased selection of highly invasive or rare native species in previous studies or because invasion success may result from mechanisms other than interspecific competitive superiority. Accordingly, interspecific per-capita competitive effects did not influence range sizes. Further studies across a broader range of environmental conditions, involving other biotic interactions that indirectly influence plant-plant interactions, may clarify when eco-evolutionary adaptations to new invaders are a relevant mechanism.
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Juliano, Steven A. "Coexistence, Exclusion, or Neutrality? A Meta-Analysis of Competition between Aedes Albopictus and Resident Mosquitoes." Israel Journal of Ecology and Evolution 56, no. 3-4 (2010): 325–51. http://dx.doi.org/10.1560/ijee.55.3-4.325.
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Competition experiments estimating the relative effects of inter- and intraspecific competition can help to resolve whether interspecific competition results in coexistence or exclusion. For mosquitoes, most such experiments have focused on invasiveAedes albopictusand its interactions with residentAedes.A meta-analysis of such experiments tested whether the effect of interspecific competition is greater than, less than, or equal to that of intraspecific competition, and whether competitive outcomes are dependent on food quality. ForA. albopictusandA. aegypti, there was significant context dependence, with interspecific competitive advantage forA. albopictuswith low food quality, and competitive equivalence with high food quality. Meta-analysis of survivorship yielded more significant effects than did estimated rate of increase. Competitive effects and competitive responses of each species yielded similar results. This meta-analysis suggests competitive exclusion ofA. aegyptibyA. albopictus, and is thus consistent with field sampling, qualitative reviews, and interpretations from individual publications. ForA. albopictusandA. triseriatus, most results indicated competitive equivalence and no context dependence, and are thus contrary to previous qualitative reviews and to interpretations from individual publications. For both pairs of species, published results suitable for meta-analysis remain scarce, and better experimental designs and improved analysis and reporting of statistical results are needed. Greater emphasis needs to be placed on estimating species' inter- and intraspecific competitive effects, rather than the more common, but theoretically less interesting, competitive responses. Experiments without low-density controls (i.e., replacement series) are inadequate for comparing competitive effects and responses.
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AGUSTO, F. B., and K. O. OKOSUN. "OPTIMAL SEASONAL BIOCONTROL FOREICHHORNIA CRASSIPES." International Journal of Biomathematics 03, no. 03 (2010): 383–97. http://dx.doi.org/10.1142/s1793524510001021.
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This article studies the effect of reduction of an invasive species' competitive ability against another aggressive species, where the intra- and inter-species competition effect on the system is modeled as a control variable. Thus, following the example of competition between water hyacinth–water lettuce, where the competitive ability of the water hyacinth is reduced by the presence of the biological agent Neochetina eichhorniae (weevil) we apply optimal control to compare the effects of the weevil on the competitive relationship. With the effect of the reduced competitive ability been obvious during the larvae stages of the weevil. An objective functional is formulated to minimize the invasive species while minimizing the cost of implementing the control. Numerical results are examined for various parameter values.
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Ursell, Tristan. "Structured environments foster competitor coexistence by manipulating interspecies interfaces." PLOS Computational Biology 17, no. 1 (2021): e1007762. http://dx.doi.org/10.1371/journal.pcbi.1007762.
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Natural environments, like soils or the mammalian gut, frequently contain microbial consortia competing within a niche, wherein many species contain genetically encoded mechanisms of interspecies competition. Recent computational work suggests that physical structures in the environment can stabilize local competition between species that would otherwise be subject to competitive exclusion under isotropic conditions. Here we employ Lotka-Volterra models to show that interfacial competition localizes to physical structures, stabilizing competitive ecological networks of many species, even with significant differences in the strength of competitive interactions between species. Within a limited range of parameter space, we show that for stable communities the length-scale of physical structure inversely correlates with the width of the distribution of competitive fitness, such that physical environments with finer structure can sustain a broader spectrum of interspecific competition. These results highlight the potentially stabilizing effects of physical structure on microbial communities and lay groundwork for engineering structures that stabilize and/or select for diverse communities of ecological, medical, or industrial utility.
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Ursell, Tristan. "Structured environments foster competitor coexistence by manipulating interspecies interfaces." PLOS Computational Biology 17, no. 1 (2021): e1007762. http://dx.doi.org/10.1371/journal.pcbi.1007762.
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Natural environments, like soils or the mammalian gut, frequently contain microbial consortia competing within a niche, wherein many species contain genetically encoded mechanisms of interspecies competition. Recent computational work suggests that physical structures in the environment can stabilize local competition between species that would otherwise be subject to competitive exclusion under isotropic conditions. Here we employ Lotka-Volterra models to show that interfacial competition localizes to physical structures, stabilizing competitive ecological networks of many species, even with significant differences in the strength of competitive interactions between species. Within a limited range of parameter space, we show that for stable communities the length-scale of physical structure inversely correlates with the width of the distribution of competitive fitness, such that physical environments with finer structure can sustain a broader spectrum of interspecific competition. These results highlight the potentially stabilizing effects of physical structure on microbial communities and lay groundwork for engineering structures that stabilize and/or select for diverse communities of ecological, medical, or industrial utility.
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Yuan, Yongge, and Junmin Li. "Effects of Parasitism on the Competitive Ability of Invasive and Native Species." Life 12, no. 11 (2022): 1800. http://dx.doi.org/10.3390/life12111800.
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Parasitic plants can often seriously harm host plants and, thus, alter competitive dominance between hosts and neighbouring species. However, whether and how parasitic plants differently affect the competitive abilities of invasive and the native plants have not been tested. In this study, we used Cuscuta grovonii as the parasitic plants and three invasive plants and three native plants as host plants. Host plants grown alone or in competition with Coix lacryma-jobi were either parasitized with Cuscuta grovonii or not parasitized. Parasitism caused similar damage to invasive and native plants when grown with Cuscuta grovonii alone but caused less damage to invasive species than native species when grown in competition. Parasitism increased the competitive ability of invasive plants but did not affect the competitive ability of native plants. In the absence of parasitism, the competitive ability of host plants was significantly negatively correlated with the competitive ability of Coix lacryma-jobi, but under parasitism, there was no significant relationship of the competitive ability between host and competitor plants. Our results indicated that parasitic plants can increase the competitive tolerance of invasive plants, but have no effect on native plants. Thus, parasitism may play an important role in the process of plant invasion.
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Altemayer, Valérie, Bruno Vincent, Pedro Naves, François Lieutier, Géraldine Roux-Morabito, and Edmundo Sousa. "Competitive interaction between Bursaphelenchus xylophilus and the closely related species Bursaphelenchus mucronatus." Nematology 10, no. 2 (2008): 219–30. http://dx.doi.org/10.1163/156854108783476403.
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AbstractBursaphelenchus xylophilus is an invasive pest of pines. When introduced accidentally into a new geographic area, it will share the same ecological niche as the closely related indigenous species, B. mucronatus. Competition between native and introduced species may affect the spread of invasive species, so we investigated the possible competitive interaction between these two nematode species transmitted by the same insect-vector, Monochamus galloprovincialis. In order to understand how the two species interacted, we compared, under laboratory conditions, their growth on fungi and pines, their ability to board M. galloprovincialis, and their competitive interaction in situations of double boarding. Bursaphelenchus xylophilus showed greater rates of growth than B. mucronatus in single and mixed treatments. The invasive species was competitively superior to the indigenous species in mixed treatments (fungi and pines). This competitive advantage in pines, prior to the beetles' infestation, could explain the greater abundance of the invasive (68%) species over the indigenous in the insect vector M. galloprovincialis. The indigenous species had no effect on beetle boarding of the invasive species. The occurrence of B. mucronatus in France and its wide distribution on numerous pine species could have an effect on B. xylophilus invasion in the initial steps of an invasion process. Nevertheless, due to the superior competitiveness of B. xylophilus, we cannot state that B. mucronatus will be efficient as a factor to decrease propagation of this invasive species.
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Srivastava, Vaibhava, Eric M. Takyi, and Rana D. Parshad. "The effect of "fear" on two species competition." Mathematical Biosciences and Engineering 20, no. 5 (2023): 8814–55. http://dx.doi.org/10.3934/mbe.2023388.
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<abstract><p>Non-consumptive effects such as fear of depredation, can strongly influence predator-prey dynamics. There are several ecological and social motivations for these effects in competitive systems as well. In this work we consider the classic two species ODE and PDE Lotka-Volterra competition models, where <italic>one</italic> of the competitors is "fearful" of the other. We find that the presence of fear can have several interesting dynamical effects on the classical competitive scenarios. Notably, for fear levels in certain regimes, we show novel bi-stability dynamics. Furthermore, in the spatially explicit setting, the effects of several spatially heterogeneous fear functions are investigated. In particular, we show that under certain integral restrictions on the fear function, a weak competition type situation can change to competitive exclusion. Applications of these results to ecological as well as sociopolitical settings are discussed, that connect to the "landscape of fear" (LOF) concept in ecology.</p></abstract>
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Broz, Amanda K., Daniel K. Manter, Ragan M. Callaway, Mark W. Paschke, and Jorge M. Vivanco. "A molecular approach to understanding plant - plant interactions in the context of invasion biology." Functional Plant Biology 35, no. 11 (2008): 1123. http://dx.doi.org/10.1071/fp08155.
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Competition is a major determinant of plant community structure, and can influence the size and reproductive fitness of a species. Therefore, competitive responses may arise from alterations in gene expression and plant function when an individual is confronted with new competitors. This study explored competition at the level of gene expression by hybridising transcripts from Centaurea maculosa Lam., one of North America’s most invasive exotic plant species, to an Arabidopsis thaliana (L.) Heynh microarray chip. Centaurea was grown in competition with Festuca idahoensis Elmer, a native species that generally has weak competitive effects against Centaurea; Gaillardia aristata Pursh, a native species that tends to be a much stronger competitor against Centaurea; and alone (control). Some transcripts were induced or repressed to a similar extent regardless of the plant neighbour grown with Centaurea. Other transcripts showed differential expression that was specific to the competitor species, possibly indicating a species-specific aspect of the competitive response of Centaurea. These results are the first to identify genes in an invasive plant that are induced or repressed by plant neighbours and provide a new avenue of insight into the molecular aspects of plant competitive ability.
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Carvalho, Saul Jorge Pinto de, and Pedro Jacob Christoffoleti. "Competition of Amaranthus species with dry bean plants." Scientia Agricola 65, no. 3 (2008): 239–45. http://dx.doi.org/10.1590/s0103-90162008000300003.
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Weeds compete with field crops mainly for water, light and nutrients, and this competition is among other factors, a function of the occurrence of weed density, and the intrinsic competitive ability of each vegetal species. The objective of this research was to evaluate the competitive ability of five weed species of the Amaranthus L. genus (A. deflexus, A. hybridus, A. retroflexus, A. spinosus and A. viridis) with dry bean plants (Phaseolus vulgaris L. - 'Carioca Precoce' cultivar), using the replacement series design. A fixed total density equivalent to 80 plants m-2 was used in pots of 2.8 L capacity varying the proportions between the species in coexistence. To install the experiment, Amaranthus seedlings were transplanted to the pots at the phenological stage of completely expanded cotyledon leaves, while the crop was seeded. A factorial scheme (5 x 5) was used to carry out the experiment, consisting of five species of Amaranthus (pigweeds) and five species proportions (beans:pigweeds): 4:0, 3:1, 2:2, 1:3 and 0:4. Randomized blocks with four replicates were installed and the experiment was repeated twice. Dry bean plants were more competitive than each one of the five Amaranthus species when the species proportion was equivalent. A. deflexus and A. viridis were the weed species which phenology were less affected by the competition with dry bean; the intraspecific competition was more damaging for dry bean plants, suggesting that the damages caused by the weeds are more related to high density of infestation than to the intrinsic competitive ability of the species.
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Chen, Yanli, Yanping Liu, Xiaoni Liu, Zhengzhong Zhang, and Feng Zhang. "The Effects of Infectious Diseases on the Consequences of Interspecific Competition in Grassland Communities." Diversity 16, no. 4 (2024): 231. http://dx.doi.org/10.3390/d16040231.
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As infectious diseases have a severe impact on the individual survival and competitive ability of host species in grassland communities, competition between relevant species may have different consequences, potentially influencing the species composition of grassland communities and the functioning of grassland ecosystems. Understanding the impact of infectious diseases on competition is thus crucial for the health management of grassland ecosystems. How do infectious diseases affect the competitive coexistence of grassland plant species? In this study, by drawing on Tilman’s multispecies competition model and incorporating the spread characteristics of grassland plant diseases, we built three spatial competition models of two grass species subject to infectious diseases, and we analyzed the invasion conditions of infectious diseases and how they impact the population dynamics and competitive consequences of the species. Our model revealed the following: (1) Diseases with high transmission rates and low virulence are more likely to invade populations, while the presence of non-host species is detrimental to disease invasion. (2) Disease promotes the coexistence of competing species, breaking down the original competition–compromise trade-off mechanism for species coexistence and greatly expanding the range of parameters within which the two species can coexist. (3) Pathogen infections indirectly weaken the suppression of inferior species by dominant species, which is similar to the cascade effect seen in trophic interactions. Our findings highlight the importance of disease in species coexistence and grassland biodiversity maintenance.
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Clarke, Anthony R., and Penelope F. Measham. "Competition: A Missing Component of Fruit Fly (Diptera: Tephritidae) Risk Assessment and Planning." Insects 13, no. 11 (2022): 1065. http://dx.doi.org/10.3390/insects13111065.
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Tephritid fruit flies are internationally significant pests of horticulture. Because they are also highly invasive and of major quarantine concern, significant effort is placed in developing full or partial pest risk assessments (PRAs) for fruit flies, while large investments can be made for their control. Competition between fruit fly species, driven by the need to access and utilise fruit for larval development, has long been recognised by researchers as a fundamental component of fruit fly biology, but is entirely absent from the fruit fly PRA literature and appears not be considered in major initiative planning. First presenting a summary of the research data which documents fruit fly competition, this paper then identifies four major effects of fruit fly competition that could impact a PRA or large-scale initiative: (i) numerical reduction of an existing fruit fly pest species following competitive displacement by an invasive fruit fly; (ii) displacement of a less competitive fruit fly pest species in space, time or host; (iii) ecological resistance to fruit fly invasion in regions already with competitively dominant fruit fly species; and (iv) lesser-pest fruit fly resurgence following control of a competitively superior species. From these four major topics, six more detailed issues are identified, with each of these illustrated by hypothetical, but realistic biosecurity scenarios from Australia/New Zealand and Europe. The scenarios identify that the effects of fruit fly competition might both positively or negatively affect the predicted impacts of an invasive fruit fly or targeted fruit fly control initiative. Competition as a modifier of fruit fly risk needs to be recognised by policy makers and incorporated into fruit fly PRAs and major investment initiatives.
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Laird and Schamp. "Competitive Intransitivity Promotes Species Coexistence." American Naturalist 168, no. 2 (2006): 182. http://dx.doi.org/10.2307/3844724.
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Laird, Robert A., and Brandon S. Schamp. "Competitive Intransitivity Promotes Species Coexistence." American Naturalist 168, no. 2 (2006): 182–93. http://dx.doi.org/10.1086/506259.
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Steers, Helen L., and Paul H. Harvey. "Species patterns: Evolution's competitive edge." Current Biology 8, no. 3 (1998): R96—R98. http://dx.doi.org/10.1016/s0960-9822(98)70056-9.
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Stone, Lewi, and Alan Roberts. "Competitive exclusion, or species aggregation?" Oecologia 91, no. 3 (1992): 419–24. http://dx.doi.org/10.1007/bf00317632.
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Elliott, Katherine J., and James M. Vose. "Evaluation of the Competitive Environment for White Pine (Pinus strobus L.) Seedlings Planted on Prescribed Burn Sites in the Southern Appalachians." Forest Science 41, no. 3 (1995): 513–30. http://dx.doi.org/10.1093/forestscience/41.3.513.
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Abstract We evaluated the competitive environment around planted white pine (Pinus strobus L.) seedlings and monitored the response of seedling growth to competition from naturally regenerating herbaceous and woody species for 2 yr after prescribed burning. We evaluated the ability of distance-independent and distance-dependent competition indices to predict resource availability, determined if white pine seedlings responded to resource reduction by competitors, and identified species-specific contributions to the competitive environment through canonical correspondence analysis (CCA). Distance-independent measures of competition were not as well correlated with pine seedling growth as were distance-dependent measures. In 1991, competition was less important in 1991 than in 1992, and ordinating the species with CCA failed to improve the predictability of the competitive environment. By 1992, competition became more important, and individual species had differing effects on pine growth; we found that light was the most important resource limiting diameter growth and that the tall tree species were responsible for reduced light availability to pine seedlings. For. Sci. 41(3):513-530.
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Germain, Rachel M., Margaret M. Mayfield, and Benjamin Gilbert. "The ‘filtering’ metaphor revisited: competition and environment jointly structure invasibility and coexistence." Biology Letters 14, no. 8 (2018): 20180460. http://dx.doi.org/10.1098/rsbl.2018.0460.
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‘Filtering’, or the reduction in species diversity that occurs because not all species can persist in all locations, is thought to unfold hierarchically, controlled by the environment at large scales and competition at small scales. However, the ecological effects of competition and the environment are not independent, and observational approaches preclude investigation into their interplay. We use a demographic approach with 30 plant species to experimentally test: (i) the effect of competition on species persistence in two soil moisture environments, and (ii) the effect of environmental conditions on mechanisms underlying competitive coexistence. We find that competitors cause differential species persistence across environments even when effects are lacking in the absence of competition, and that the traits which determine persistence depend on the competitive environment. If our study had been observational and trait-based, we would have erroneously concluded that the environment filters species with low biomass, shallow roots and small seeds. Changing environmental conditions generated idiosyncratic effects on coexistence outcomes, increasing competitive exclusion of some species while promoting coexistence of others. Our results highlight the importance of considering environmental filtering in the light of, rather than in isolation from, competition, and challenge community assembly models and approaches to projecting future species distributions.
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Richter-Boix, Alex, Gustavo Llorente, and Albert Montori. "Hierarchical competition in pond-breeding anuran larvae in a Mediterranean area." Amphibia-Reptilia 28, no. 2 (2007): 247–61. http://dx.doi.org/10.1163/156853807780202549.
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AbstractThe anuran larval guild is frequently characterised by the co-occurrence, with high niche overlap, of distinct species in the same pond at variables densities during development. Anuran larvae have therefore been widely studied as a model system for competition. Body size and activity level are considered the most important factors that influence the outcome of competition between tadpoles. As species from temporary ponds normally show higher activity levels in order to achieve rapid growth and thus reduce the risk of desiccation, these species are often considered superior competitors. We designed several laboratory experiments to examine the intra- and interspecific effects on growth rate, mass at metamorphosis and survival to metamorphosis of six species in a Mediterranean area. Body size and activity level were used as explanatory covariables to determine competitive ability among species. An asymmetric and hierarchical relationship was found among the six species. Larger tadpole species were more successful in competitive interactions than smaller ones, but no relationship was found between activity level and competition effects. Species typically found in temporary ponds (Pelodytes punctatus and Bufo calamita) were considered poor competitors in contrast with other communities studied. Species with low competitive ability can persist by using refuges in which competition is reduced (e.g. ephemeral ponds).
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Bernhardt, Joey R., Pavel Kratina, Aaron Louis Pereira, Manu Tamminen, Mridul K. Thomas, and Anita Narwani. "The evolution of competitive ability for essential resources." Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1798 (2020): 20190247. http://dx.doi.org/10.1098/rstb.2019.0247.
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Competition for limiting resources is among the most fundamental ecological interactions and has long been considered a key driver of species coexistence and biodiversity. Species' minimum resource requirements, their R *s, are key traits that link individual physiological demands to the outcome of competition. However, a major question remains unanswered—to what extent are species’ competitive traits able to evolve in response to resource limitation? To address this knowledge gap, we performed an evolution experiment in which we exposed Chlamydomonas reinhardtii for approximately 285 generations to seven environments in chemostats that differed in resource supply ratios (including nitrogen, phosphorus and light limitation) and salt stress. We then grew the ancestors and descendants in a common garden and quantified their competitive abilities for essential resources. We investigated constraints on trait evolution by testing whether changes in resource requirements for different resources were correlated. Competitive abilities for phosphorus improved in all populations, while competitive abilities for nitrogen and light increased in some populations and decreased in others. In contrast to the common assumption that there are trade-offs between competitive abilities for different resources, we found that improvements in competitive ability for a resource came at no detectable cost. Instead, improvements in competitive ability for multiple resources were either positively correlated or not significantly correlated. Using resource competition theory, we then demonstrated that rapid adaptation in competitive traits altered the predicted outcomes of competition. These results highlight the need to incorporate contemporary evolutionary change into predictions of competitive community dynamics over environmental gradients. This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.
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Aarssen, L. W., and Roy Turkington. "Competitive relations among species from pastures of different ages." Canadian Journal of Botany 63, no. 12 (1985): 2319–25. http://dx.doi.org/10.1139/b85-331.
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All possible pairs of Dactylis glomerate, Holcus lanatus, Lolium perenne, Poa compressa, and Trifolium repens were collected where the species pairs occurred in close proximity in pastures that were 2, 21, and 40 years old. Each clone was grown with its natural neighbouring clone in experimental field plots for a period of 1 year. Differences in competitive relations between two species from pastures of different ages were measured by total mixture yield and component yield quotient, i.e., the yield quotient of the lowest and highest yielding components. Results show that the relative competitive abilities of particular species differ markedly depending on the age of the pasture from which the plants were collected. Very little support is given for the traditional view that selection pressures from competition usually result in the evolution of niche differentiation in the component species of a community. Alternative evolutionary consequences of competition permitting coexistence are discussed.
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Sepkoski, J. John, Frank K. McKinney, and Scott Lidgard. "Competitive displacement among post-Paleozoic cyclostome and cheilostome bryozoans." Paleobiology 26, no. 1 (2000): 7–18. http://dx.doi.org/10.1666/0094-8373(2000)026<0007:cdappc>2.0.co;2.
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Encrusting bryozoans provide one of the few systems in the fossil record in which ecological competition can be observed directly at local scales. The macroevolutionary history of diversity of cyclostome and cheilostome bryozoans is consistent with a coupled-logistic model of clade displacement predicated on species within clades interacting competitively. The model matches observed diversity history if the model is perturbed by a mass extinction with a position and magnitude analogous to the Cretaceous / Tertiary boundary event. Although it is difficult to measure all parameters in the model from fossil data, critical factors are intrinsic rates of extinction, which can be measured. Cyclostomes maintained a rather low rate of extinction the model solutions predict that they would lose diversity only slowly as competitively superior species of cheilostomes diversified into their environment. Thus, the microecological record of preserved competitive interactions between cyclostome and cheilostome bryozoans and the macroevolutionary record of global diversity are consistent in regard to competition as a significant influence on diversity histories of post-Paleozoic bryozoans.
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Miyamoto, Y., and T. Noda. "Effects of mussels on competitively inferior species: competitive exclusion to facilitation." Marine Ecology Progress Series 276 (2004): 293–98. http://dx.doi.org/10.3354/meps276293.
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Zhang, Quan-Guo, and Da-Yong Zhang. "Competitive hierarchies inferred from pair-wise and multi-species competition experiments." Acta Oecologica 38 (January 2012): 66–70. http://dx.doi.org/10.1016/j.actao.2011.09.005.
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Guglielmini, A. C., A. M. C. Verdú, and E. H. Satorre. "Competitive ability of five common weed species in competition with soybean." International Journal of Pest Management 63, no. 1 (2016): 30–36. http://dx.doi.org/10.1080/09670874.2016.1213459.
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MacInnis, Amber E., and Leon G. Higley. "Competition Among Three Forensically Important Blow Fly Species (Diptera: Calliphoridae): Phormia regina, Lucilia sericata, and Chrysomya rufifacies." Environmental Entomology 49, no. 6 (2020): 1473–79. http://dx.doi.org/10.1093/ee/nvaa120.
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Abstract Avoiding competition is thought to explain insect successional patterns on carrion, but few studies have looked at competition directly. We use replacement series experiments with three species of blow flies: Phormia regina (Meigen) (Diptera: Calliphoridae), Lucilia sericata (Meigen) (Diptera:Calliphoridae), and Chrysomya rufifacies (Macquart) (Diptera:Calliphoridae) to characterize competitive relationships. From experimental results, P. regina showed a significant competitive advantage over L. sericata. Infestation of carrion differs between L. sericata and P. regina; specifically, L. sericata oviposits on carrion without any delay, while P. regina typically delays oviposition. Our findings are consistent with the notion that differences in oviposition times represent a mechanism for L. sericata to avoid potential competition. Competition by C. rufifacies differs since C. rufifacies, in the event of a limited food supply, will prey on other maggot species. In replacement series experiments, C. rufifacies killed all P. regina in mixed treatments, representing an ultimate competitive advantage. In the United States, these two species do not often overlap because of differences in seasonal distribution. However, with climate change, phenological separation may grow less distinct. Surprisingly, in replacement series experiments with C. rufifacies and L. sericata, no competitive interactions were observed. In other studies, L. sericata has been shown to form clusters away from predaceous maggots, allowing improved survival, which may account for the absence of predation by C. rufifacies. Finally, this study shows that replacement series models are useful in measuring competition, supporting the notion that interspecific competition between necrophagous insect species may have driven life history traits of those species.
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Hart, Simon P., Martin M. Turcotte, and Jonathan M. Levine. "Effects of rapid evolution on species coexistence." Proceedings of the National Academy of Sciences 116, no. 6 (2019): 2112–17. http://dx.doi.org/10.1073/pnas.1816298116.
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Increasing evidence for rapid evolution suggests that the maintenance of species diversity in ecological communities may be influenced by more than purely ecological processes. Classic theory shows that interspecific competition may select for traits that increase niche differentiation, weakening competition and thus promoting species coexistence. While empirical work has demonstrated trait evolution in response to competition, if and how evolution affects the dynamics of the competing species—the key step for completing the required eco-evolutionary feedback—has been difficult to resolve. Here, we show that evolution in response to interspecific competition feeds back to change the course of competitive population dynamics of aquatic plant species over 10–15 generations in the field. By manipulating selection imposed by heterospecific competitors in experimental ponds, we demonstrate that (i) interspecific competition drives rapid genotypic change, and (ii) this evolutionary change in one competitor, while not changing the coexistence outcome, causes the population trajectories of the two competing species to converge. In contrast to the common expectation that interspecific competition should drive the evolution of niche differentiation, our results suggest that genotypic evolution resulted in phenotypic changes that altered population dynamics by affecting the competitive hierarchy. This result is consistent with theory suggesting that competition for essential resources can limit opportunities for the evolution of niche differentiation. Our finding that rapid evolution regulates the dynamics of competing species suggests that ecosystems may rely on continuous feedbacks between ecology and evolution to maintain species diversity.
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Ilic-Milosevic, Marijana, Olivera Petrovic-Obradovic, Sasa Stankovic, et al. "Estimation of the competitiveness of Ephedrus plagiator in relation to other parasitoids from the subfamily Aphidiinae." Archives of Biological Sciences 72, no. 1 (2020): 53–61. http://dx.doi.org/10.2298/abs190923066i.
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The parasitoid species Ephedrus plagiator (Nees, 1811) (Hymenoptera: Aphidiinae) is one of the most important biological agents against pest aphids. We investigated whether this species was in competition with some other aphidiine species for the same hosts. We thus examined its potential in biological programs to control aphids. We applied an unsupervised artificial neural network, a self-organizing map (SOM), which classified the competitive parasitoids into seven groups. The SOM also visualized the distributional pattern of 31 parasitoid wasps along the neural network, revealing their competitive ability in relation to E. plagiator. Indicator value (IndVal) analysis quantified the competitive ability and showed that the most competitive species with regard to E. plagiator were Lysiphlebus testaceipes (Cresson, 1880), L. fabarum (Marshall 1896), L. cardui (Marshall 1896) and Binodoxys angelicae (Haliday, 1833). These species appeared in four different SOM groups and mostly parasitized the Aphis fabae Scopoli, 1763 (Hemiptera: Aphididae) host.
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Burton, Philip J. "Some limitations inherent to static indices of plant competition." Canadian Journal of Forest Research 23, no. 10 (1993): 2141–52. http://dx.doi.org/10.1139/x93-267.
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Various measurements of the abundance, proximity, and stature of neighbouring plants are utilized as indices of competitive intensity experienced by crop trees. These indices can be useful in assessing the desirability of vegetation control and stand thinnings, and in simulating stand development. Static competition indices, however, have fundamental limitations which should be more widely considered. Competition is usually a constraint to growth, not a determinant of growth, so any measurement of competition alone is fundamentally limited in its ability to predict individual crop tree performance. Differences in the microsite effects of competitors and the autecological responses of crop species result in wide variation in the size of the functional competitive arena, and suggest the need for distinct weightings of competitive intensity for different combinations of species and site. Site differences and weather variation, when coupled with species differences in above- and below-ground allocation, will alter the mode and intensity of competition within a stand and from year to year. The phenology of competitors and focal species will likewise alter interference patterns within a year, making one-time measurements sometimes misleading. Suggested alternatives for determining the importance and intensity of competition include the maintenance of competition-free seedlings ("phytometers") in order to gauge the competitive constraints experienced elsewhere in a plantation. Simulation models of tree growth and stand development also show promise, but they must incorporate the dynamics of noncrop vegetation development. In developing guidelines for the assessment of noncrop interference and the advisability of vegetation control, there is still a need to determine, in a generalizable manner, appropriate survey plot sizes and critical competition thresholds for different combinations of site type, crop species, and vegetation complex.
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BA, Idy, Papa Ibrahima NDIAYE, Mahe Ndao, and AboubaKary Diakhaby. "An Extension of Two Species Lotka-Volterra Competition Model." Biomath Communications 8, no. 2 (2021): 90. http://dx.doi.org/10.11145/bmc.2021.12.171.
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Limiting resource is a angular stone of the interactions between species in ecosystems such as competition, prey-predators and food chain systems. In this paper, we propose a planar system as an extension of Lotka-Voterra competition model. This describes? two competitive species for a single resource? which are affected by intra and inter-specific interference. We give its complete analysis for the existence and local stability of all equlibria and some conditions of global stability. The model exhibits a rich set of behaviors with a multiplicity of coexistence equilibria, bi-stability, tri-stability and occurrence of global stability of the exclusion of one species and the coexistence? equilibrium. The asymptotic behavior and the number of coexistence equilibria are shown by a saddle-node bifurcation of the level of resource under conditions on competitive effects relatively to associated growth rate per unit of resource.Moreover, we determine the competition outcome in the situations of Balanced and Unbalanced intra-inter species competition effects. Finally, we illustrate results by numerical simulations.
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Hasegawa, Koh, and Koji Maekawa. "Role of visual barriers on mitigation of interspecific interference competition between native and non-native salmonid species." Canadian Journal of Zoology 87, no. 9 (2009): 781–86. http://dx.doi.org/10.1139/z09-071.
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Interspecific competition is a mechanism by which native salmonids can be replaced by non-native species. According to the two-species Lotka–Volterra competition model, replacement of the native species would occur when the non-native species has a competitive advantage over the native species and interspecific competition is more intense than competition within each of the two species. However, field observations have implied that visual barriers such as woody debris may slow down the replacement by mitigating interspecific competition. Using an experimental stream with white-spotted charr ( Salvelinus leucomaenis (Pallas, 1814)) as the native species and brown trout ( Salmo trutta L., 1758) as the non-native species, this study examined aggressive actions within and between species to assess the relative intensities of interspecific and intraspecific competitons within native species and the effect of visual barriers for reducing the relative intensity. In a sympatric and no-barrier treatment where trout was the dominant species, interspecific competition occurred more intensely than intraspecific competition among native charr. However, the relative intensity of interspecific competition decreased in a sympatric and with-barrier treatment. Our results suggest that interspecific competition may contribute to the replacement of native species by more competitive, non-native species. However, restoring visual barriers is a potential method to mitigate interference interactions and may deter the replacement.
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Keddy, Paul A. "Effects of competition from shrubs on herbaceous wetland plants: a 4-year field experiment." Canadian Journal of Botany 67, no. 3 (1989): 708–16. http://dx.doi.org/10.1139/b89-094.
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While competition is known to occur among some species in some plant communities, we are not yet able to predict in which environments, or among which species, competitive interactions will be most intense. The objective of this study was to test for competition in a wetland plant community and then to determine which environments and which species were influenced by competition. The study site was the transition zone between shrubs and herbaceous plants on a lakeshore. To test for competitive release, shrubs were removed from treatment plots paired with controls in 25 sections of shoreline and cover of herbaceous species was monitored for 4 years. There were highly significant increases in cover, richness, and diversity in the removal plots, but less than one quarter of the individual species responded significantly. In general, these were small, partly evergreen species with high densities of buried seeds (e.g., Drosera intermedia, Hypericum boréale). On shores with frequent disturbance and low fertility there was no evidence for competitive release. The reduction in plant cover during a summer with high water levels suggests that lakeshores shift from abiotic to biotic structuring according to the water level in a particular year or series of years. Superimposed upon this is variation attributable to the type of shoreline and the type of species. Key words: competition, disturbance, exposure, lakeshores, Myrica gale, shrubs, wetlands, zonation.
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Martignoni, Maria M., Miranda M. Hart, Rebecca C. Tyson, and Jimmy Garnier. "Diversity within mutualist guilds promotes coexistence and reduces the risk of invasion from an alien mutualist." Proceedings of the Royal Society B: Biological Sciences 287, no. 1923 (2020): 20192312. http://dx.doi.org/10.1098/rspb.2019.2312.
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Biodiversity is an important component of healthy ecosystems, and thus understanding the mechanisms behind species coexistence is critical in ecology and conservation biology. In particular, few studies have focused on the dynamics resulting from the co-occurrence of mutualistic and competitive interactions within a group of species. Here we build a mathematical model to study the dynamics of a guild of competitors who are also engaged in mutualistic interactions with a common partner. We show that coexistence as well as competitive exclusion can occur depending on the competition strength and on strength of the mutualistic interactions, and we formulate concrete criteria for predicting invasion success of an alien mutualist based on propagule pressure, alien traits (such as its resource exchange ability) and composition of the recipient community. We find that intra guild diversity promotes the coexistence of species that would otherwise competitively exclude each other, and makes a guild less vulnerable to invasion. Our results can serve as a useful framework to predict the consequences of species manipulation in mutualistic communities.
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GALON, LEANDRO, RICARDO TREVISOL, CESAR TIAGO FORTE, SIUMAR PEDRO TIRONI, FRANCISCO WILSON REICHERT JÚNIOR, and ANDRÉ LUIZ RADUNZ. "COMPETITIVE ABILITY OF BEAN CULTIVARS WITH HAIRY BEGGARTICKS." Revista Caatinga 30, no. 4 (2017): 855–65. http://dx.doi.org/10.1590/1983-21252017v30n405rc.
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ABSTRACT Weed interference is a factor that limits the productivity of beans and, among these, hairy beggarticks is one of the main species competing with the crop for environmental resources. Thus, the aim of this study is to evaluate the competitive ability of black bean cultivars (BRS Campeiro, IPR Uirapuru, SCS204 Predileto and BRS Supremo) in the presence of a biotype of hairy beggarticks. The experimental design is a completely randomized block with four replications. Treatments were arranged in a replacement series, consisting of a proportion of the crop and the hairy beggarticks: 100:0; 75:25; 50:50: 24:75, and 0:100, which corresponds to 40:0, 30:10, 20:20, 10:30, and 0:40 plant pots1. We accomplished competitive analysis through diagrams applied to the replacement series, as well as using relative competitive indices. The leaf area and shoot dry mass were evaluated at 40 days after emergence of the species. There was competition between bean cultivars and hairy beggarticks for the same environmental resources, causing negative interference in the growth of the species, independent of the proportion of plants. Bean cultivars had a lower relative loss by reducing the morphological variables of the hairy beggarticks, thereby demonstrating superiority in its competitive ability in relation to the weed. Interspecific competition is less damaging than intraspecific competition for both species.
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Canham, Charles D., Philip T. LePage, and K. Dave Coates. "A neighborhood analysis of canopy tree competition: effects of shading versus crowding." Canadian Journal of Forest Research 34, no. 4 (2004): 778–87. http://dx.doi.org/10.1139/x03-232.
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We have developed extensions of traditional distance-dependent, spatial competition analyses that estimate the magnitude of the competitive effects of neighboring trees on target tree growth as a function of the species, size, and distance to neighboring trees. Our analyses also estimate inter- and intra-specific competition coefficients and explicitly partition the competitive effects of neighbors into the effects of shading versus crowding. We tested the method using data from forests of northern, interior British Columbia dominated by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don). For both species, the most parsimonious regression models included terms for the effects of tree size, crowding, and shading and separate competitive effects of four different groups of competing species. The models explained 33%59% of the variation in radial growth of the two species. For both species, growth declined more steeply as a function of crowding than shading. There was striking asymmetry in the strength of interspecific competition between hemlock and redcedar, with crowding by hemlock having a strong per capita effect on redcedar, while crowding by redcedar had relatively little effect on the radial growth of hemlock.
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Xue, Wei, Lin Huang, and Fei-Hai Yu. "Importance of starting points in heterogeneous environments: interactions between two clonal plants with contrasting spatial architectures." Journal of Plant Ecology 13, no. 3 (2020): 323–30. http://dx.doi.org/10.1093/jpe/rtaa018.
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Abstract Aims Plants can benefit from heterogeneous environments via disproportionately increasing resource harvesting in resource-rich patches. Their initial growing positions with respect to resource patches may thus have important influences on their performance and relative competitive ability. Such impacts may differ between species with contrasting spatial architectures. However, the potential influence of initial growing positions in heterogeneous environment on plant growth and competition has largely been ignored. Methods We grew the phalanx plant Carex neurocarpa and the guerrilla plant Bolboschoenus planiculmis alone or in competition in a heterogeneous environment consisting of high- and low-nutrient soil patches. In treatments without competition, one ramet of each species was grown in either a high- or a low-nutrient patch in the heterogeneous environment. In treatments with competition, a ramet of the target species was grown in either a high- or a low-nutrient patch, and a ramet of the competitor species was grown in the same patch as the target species or an adjacent patch with a different nutrient level. Important Findings Without competition C. neurocarpa produced more biomass and ramets when initially grown in a high-nutrient patch than when initially grown in a low-nutrient patch. With competition, these differences disappeared. Consequently, competitive intensity on C. neurocarpa was higher when it initially grew in a high-nutrient patch than when it initially grew in a low-nutrient patch. These impacts were independent of the initial position of its competitor. By contrast, the initial positions of B. planiculmis did not influence its growth or competitive response. Therefore, in heterogeneous environments, initial growing positions of clonal plants may influence their performance in competition-free environments and may also affect their relative competitive ability, and these effects may depend on spatial architecture of the plants.
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Hung, Li-Chang. "Competitive Gompertz model of two species." Differential Equations & Applications, no. 3 (2014): 295–307. http://dx.doi.org/10.7153/dea-06-16.
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., S. M. Rezaul Karim. "Competitive Ability of Different Weed Species." Journal of Agronomy 1, no. 3 (2002): 116–18. http://dx.doi.org/10.3923/ja.2002.116.118.
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Icenhour, Crystal R., Jonathan Arnold, Mario Medvedovic, and Melanie T. Cushion. "Competitive coexistence of two Pneumocystis species." Infection, Genetics and Evolution 6, no. 3 (2006): 177–86. http://dx.doi.org/10.1016/j.meegid.2005.03.004.
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Šajna, Nina, and Primož Kušar. "Modeling species fitness in competitive environments." Ecological Modelling 275 (March 2014): 31–36. http://dx.doi.org/10.1016/j.ecolmodel.2013.12.007.
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