Bibliografie tematiche / Competitive species

Letteratura scientifica selezionata sul tema "Competitive species"

Autore: Grafiati

Pubblicato: 8 giugno 2024

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Articoli di riviste sul tema "Competitive species":

Borgström, Pernilla, Joachim Strengbom, Maria Viketoft e Riccardo Bommarco. "Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect". PeerJ 4 (4 aprile 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.

Collins, B., e G. R. Wein. "Competition between native and immigrant Polygonum congeners". Canadian Journal of Botany 71, n. 7 (1 luglio 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.

Neill, Paula E., Nicolás Rozbaczylo, Cristóbal Villaseñor-Parada, Garen Guzmán-Rendón, Sandra Sampértegui e 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 (24 aprile 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.

Verhoeven, Michael R., Wesley J. Glisson e Daniel J. Larkin. "Niche Models Differentiate Potential Impacts of Two Aquatic Invasive Plant Species on Native Macrophytes". Diversity 12, n. 4 (23 aprile 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.

Moral, Roger del. "Competitive effects on the structure of subalpine meadow communities". Canadian Journal of Botany 63, n. 8 (1 agosto 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.

Sánchez-García, Daniel, Xim Cerdá e Elena Angulo. "Temperature or competition: Which has more influence on Mediterranean ant communities?" PLOS ONE 17, n. 4 (29 aprile 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.

Vera, María Carmen, Marcos Marvá, Víctor José García-Garrido e René Escalante. "The Beddington–DeAngelis Competitive Response: Intra-Species Interference Enhances Coexistence in Species Competition". Mathematics 12, n. 4 (13 febbraio 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.

Dungan, Michael L. "Competition and the morphology, ecology, and evolution of acorn barnacles: an experimental test". Paleobiology 11, n. 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.

Larocque, Guy R., Nancy Luckai, Shailendra N. Adhikary, Arthur Groot, F. Wayne Bell e 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, n. 2 (giugno 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.

Hasibuan, Arjun, Asep Kuswandi Supriatna e Ema Carnia. "Mathematical Model of Iteroparous and Semelparous Species Interaction". CAUCHY: Jurnal Matematika Murni dan Aplikasi 7, n. 3 (11 ottobre 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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Tesi sul tema "Competitive species":

Roney, Hillary Christine. "Competitive Exclusion of Cyanobacterial Species in the Great Salt Lake". Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2476.pdf.

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Morghan, Kimberly Jo Reever. "Competitive interactions between native grasses and invasive species in California grasslands /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.

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Ross, Pamela. "Caesium-137 uptake in two grass species and the effects of competitive ions". Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389595.

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ICENHOUR, CRYSTAL RENEE PERRY. "EXPERIMENTAL EVIDENCE FOR COMPETITIVE COEXISTENCE OF TWO SPECIES OF PNEUMOCYSTIS WITHIN RAT LUNGS". University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1012244966.

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Thomas, Heather M. "Competitive Interactions Between a Native and Exotic Trout Species in High Mountain Streams". DigitalCommons@USU, 1996. https://digitalcommons.usu.edu/etd/5264.

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Populations of the introduced book trout, Salvelinus fontinalis, have recently become more widespread and abundant in western North American streams, possible at the expense of native Colorado River cutthroat trout, Oncorhynchus clarki pleuriticus. We examined the intensity and potential mechanism of competition between these species. Feeding experiments in laboratory stream channels showed that cutthroat trout feeding efficiency decreases in the presence of a brook trout. Decreased feeding efficiency appeared to be due to interference, as cutthroat trout were inactive in the presence of the brook trout. Evidence for interference competition in the feeding experiments was also given by the fact that brook trout feeding efficiency was lower than the feeding efficiency of cutthroat trout. The decreased feeding efficiency of cutthroat trout in the presence of brook trout was due to decreased attack rates by cutthroat trout, and was not due to attacks and consumption of the food items by the brook trout. A field enclosure experiment, in which riffle-pool sections of a stream were isolated by fencing, was performed to determine if the presence of brook trout had a negative effect on the growth, fat content, and diet of cutthroat trout. Cutthroat trout fat levels were significantly lower in the presence of brook trout. The growth of cutthroat trout was not significantly different in the presence and absence of brook trout, but there was a trend fro lower growth of cutthroat trout in the presence of brook trout. Diet choices and total biomass of prey consumed by cutthroat trout in the field experiment and in a survey of three streams were not affected by the presence of brook trout. The observed decreased feeding efficiency of cutthroat trout in the presence of brook trout may be the mechanism responsible for the significant;y decreased fat levels during the relatively short, summer growing season and may result in reduced population sizes due to high overwinter mortality and delayed sexual maturity.

Pohl, Angelika [Verfasser], e Niels [Akademischer Betreuer] Dingemanse. "An analysis of competitive traits in pest ant species / Angelika Pohl ; Betreuer: Niels Dingemanse". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1198111844/34.

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Schwartz, Lauren Michele. "The competitive response of Panicum virgatum cultivars to non-native invasive species in southern Illinois". OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/765.

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Historically, the tallgrass prairie (TGP) was the largest ecosystem in North America, but today only about 10-15% of the original extent exists today. Some areas have experienced more extreme loss, for example in the state of Illinois less than 0.01% of high-quality native tallgrass prairie remains. Non-native invasive species are a recent phenomenon that threatens the integrity of surviving TGP communities. Ecotypes of dominant C4 grasses are the basis of numerous cultivars, many of which are utilized in prairie restorations. In this study, the effects of three invasive species (Bromus inermis, Schedonorus phoenix, and Poa pratensis) on two lowland (`Alamo' and `Kanlow') and three upland (`Blackwell', `Cave in Rock', and `Trailblazer') cultivars of the dominant C4 grass Panicum virgatum were tested. Two simple pair-wise greenhouse experiments were established in which cultivars were sown as a monoculture or as a mixture of the cultivars with one of three invasive species. Pots were subjected to one of two water treatments with three replicates of each treatment combination. Response variables (height, number of leaves, tiller density, and biomass) and resources (soil moisture, soil pH, soil electrical conductivity, and light intensity) were measured. The greenhouse studies showed that response variables were affected by the presence of invasive species and that the time of growth affected resource levels. Resources are allocated to different areas (i.e growth and reproduction) when competition and stress are implemented on the dominant species. This study was the first to experimentally test for the presence of the physiological stress marker, trigonelline, in a prairie grass. Trigonelline was highest in upland cultivars under low moisture and highest in lowland cultivars under low moisture treatments. The results of these greenhouse studies suggest that invasive species may differentially affect cultivars of Panicum virgatum that may be sown in a prairie restoration. Performance of the P. virgatum cultivars was dependent on the timing of growth, the pot size, the invasive species, as well as soil moisture level. Therefore, when choosing a cultivar source for restoration, resources (i.e. soil moisture) should be looked into to maximize the output of the cultivar.

Nielsen, Kristin Norma Astrid Toftgaard. "Predicting competitive ability from plant traits: A comparative study of 63 terrestrial herbaceous plant species". Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10227.

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There is critical need for studies on interspecific competition which enable general principles to be deduced that apply beyond the species and conditions of a particular study or site. Studies on plant traits are a key part of this search for general principles. I measured relative competitive ability in 63 terrestrial herbaceous plant species using the phytometer Trichostema brachiatum, to test whether competitive ability can be predicted from simple measurable plant traits. The test species utilised in this experiment represented a wide array of terrestrial vegetation types (e.g. rock. barrens, alvars, old fields), and an array of growth forms, from small rosette species (e.g. Saxifraga virginiensis) to large clonal graminoids (e.g. Agropyron repens). The experiment was carried out under both a "normal" and a "drought" treatment. Multiple linear regression showed that there was a strong relationship between plant traits and competitive ability (Normal treatment--r$\sp2$ = 0.54; Drought--treatment r$\sp2$ = 0.55). Total plant biomass explained 34% of the variation in competitive ability in the normal treatment and below-ground biomass explained 35% of the variation in the drought treatment. Leaf shape explained most of the residual variation. The competitive hierarchy for plants in the normal and drought treatment was compared. Rankings for individual species varied between treatments, however, when all species were compared simultaneously, competitive hierarchies in both treatments were highly correlated (r$\sb{\rm s}$ = 0.91). This suggests that invariant and variant views of competitive hierarchies are not mutually exclusive but instead depend on the scale at which competition is being addressed. On the broad scale, relative competitive abilities appear consistent across different environments. Thus, both traits and hierarchies show general repeatable patterns that allow us to generalize from one set of circumstances to another.

Kiger, Sarah. "Competitive ability of native and non-native prairie species in response to soil nitrogen and density". Connect to resource, 2006. http://hdl.handle.net/1811/6621.

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Thesis (Honors)--Ohio State University, 2006.
Title from first page of PDF file. Document formatted into pages: contains 21 p.; also includes graphics. Includes bibliographical references (p. 12-13). Available online via Ohio State University's Knowledge Bank.

Long, Michael A. "Tree species composition and oak competitive status in upland hardwood stands approaching mid-rotation in southern Illinois /". Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1404346481&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Libri sul tema "Competitive species":

1954-, Comeau P. G., Haeussler S, Canada Forestry Canada, British Columbia. Ministry of Forests., Canada-British Columbia Forest Resource Development Agreement. e Canada/BC Economic & Regional Development Agreement., a cura di. Autecology, biology, competitive status and response to treatment of seven southern interior weed species. Victoria, B.C: Forestry Canada, 1989.

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Program of Research on the Economics of Invasive Species Management (U.S.). Program of Research on the Economics of Invasive Species Management: Fiscal 2003 : competitive grants and cooperative agreements program: description and application process. Washington, D.C.]: U.S. Dept. of Agriculture, Economic Research Service, Program of Research on the Economics of Invasive Species Management, 2003.

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Evill, Neil Kenneth. Clonal and species competition in aphids. Birmingham: University of Birmingham, 1999.

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Resources, United States Congress House Committee on Merchant Marine and Fisheries Subcommittee on Environment and Natural. Introduction of harmful non-indigenous species into the United States: Hearing before the Subcommittee on Environment and Natural Resources of the Committee on Merchant Marine and Fisheries, House of Representatives, One Hundred Third Congress, first session ... October 5, 1993. Washington: U.S. G.P.O., 1994.

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United States. Congress. Office of Technology Assessment, a cura di. Harmful non-indigenous species in the United States: Summary. [Washington, DC]: The Office, 1993.

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Grossman, Gene M. Electoral competition and special interest politics. Cambridge, MA: National Bureau of Economic Research, 1994.

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Fish, John. Managing special education: Codes, charters, and competition. Buckingham: Open University Press, 1995.

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National Institute of Justice (U.S.), a cura di. Special initiative on drug program evaluations: A competitive research solicitation. [Washington, D.C.]: U.S. Dept. of Justice, Office of Justice Programs, National Institute of Justice, 1990.

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National Institute of Justice (U.S.), a cura di. Special initiative on drug program evaluations: A competitive research solicitation. [Washington, D.C.]: U.S. Dept. of Justice, Office of Justice Programs, National Institute of Justice, 1990.

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Judy, Allen. Marketing your event planning business: A creative approach to gaining the competitive edge. Mississauga, Ont: Wiley, 2004.

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Capitoli di libri sul tema "Competitive species":

Wandrag, Elizabeth M., e Jane A. Catford. "Competition between native and non-native plants." In Plant invasions: the role of biotic interactions, 281–307. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0281.

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Abstract The introduction of species to new locations leads to novel competitive interactions between resident native and newly-arriving non-native species. The nature of these competitive interactions can influence the suitability of the environment for the survival, reproduction and spread of non-native plant species, and the impact those species have on native plant communities. Indeed, the large literature on competition among plants reflects its importance in shaping the composition of plant communities, including the invasion success of non-native species. While competition and invasion theory have historically developed in parallel, the increasing recognition of the synergism between the two themes has led to new insights into how non-native plant species invade native plant communities, and the impacts they have on those plant communities. This chapter provides an entry point into the aspects of competition theory that can help explain the success, dominance and impacts of invasive species. It focuses on resource competition, which arises wherever the resources necessary for establishment, survival, reproduction and spread are in limited supply. It highlights key hypotheses developed in invasion biology that relate to ideas of competition, outlines biotic and abiotic factors that influence the strength of competition and species' relative competitive abilities, and describes when and how competition between non-native and native plant species can influence invasion outcomes. Understanding the processes that influence the strength of competition between non-native and native plant species is a necessary step towards understanding the causes and consequences of biological invasions.

Brown, Theodore L., e Richard J. Sullivan. "Competitive Reactivities of Paramagnetic Organometallic Intermediates". In Paramagnetic Organometallic Species in Activation/Selectivity, Catalysis, 187–200. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0877-2_13.

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Hajn, Petr. "O konkurenci i spolupráci při soutěžení". In Pocta prof. Josefu Bejčkovi k 70. narozeninám, 29–34. Brno: Masaryk University Press, 2022. http://dx.doi.org/10.5817/cz.muni.p280-0094-2022-1.

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Huang, Dejian, e Restituto Tocmo. "Assays based on competitive measurement of the scavenging ability of reactive oxygen/nitrogen species". In Measurement of Antioxidant Activity & Capacity, 21–38. Chichester, UK: John Wiley & Sons, Ltd, 2017. http://dx.doi.org/10.1002/9781119135388.ch2.

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Stelzer, Claus-Peter. "Population growth in planktonic rotifers. Does temperature shift the competitive advantage for different species?" In Rotifera VIII: A Comparative Approach, 349–53. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-4782-8_46.

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Roth, Justine P. "Structure and Reactivity of Copper-Oxygen Species Revealed by Competitive Oxygen-18 Isotope Effects". In Copper-Oxygen Chemistry, 169–95. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118094365.ch6.

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Chesson, Peter. "Species species Competition species competition and Predation species predation". In Encyclopedia of Sustainability Science and Technology, 10061–85. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-0851-3_579.

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Smith-Ramesh, Lauren M. "Allelopathic disruptions of biotic interactions due to non-native plants." In Plant invasions: the role of biotic interactions, 270–80. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0270.

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Abstract Allelopathy, or the process by which plants influence the growth and performance of their neighbours through the release of chemicals, may play a key role in mediating the impacts of non-native invasive species on their neighbours. The Novel Weapons Hypothesis purports that non-native invasive species are in part successful because they produce harmful allelochemicals to which resident species are particularly susceptible because residents lack a shared evolutionary history with the invader. While allelopathic non-native invaders may reduce the growth and performance of neighbours through direct phytotoxicity, they may more often exert negative impacts through disruption of biotic interactions among resident species. Allelopathy by non-native plants may disrupt mutualisms between resident plants and microbes, plant-herbivore interactions or existing competitive and facilitative interactions among resident plants. For example, several non-native plants are known to disrupt the mutualism between resident plants and mycorrhizal fungi, reducing resident plant fitness to the benefit of the invader. Allelopathic non-natives may also disrupt interactions among resident plants and their herbivores when allelochemicals also influence herbivore behaviour or fitness. Alternatively, biotic interactions can also be protective for resident species, which may be less susceptible to the impacts of non-native species when their mutualisms are intact. As we advance our understanding of allelopathy and its role in mediating the impacts of invasive plant species, we may gain new insights by viewing invasions within a network context rather than focusing on pairwise interactions.

Kuebbing, Sara E. "How direct and indirect non-native interactions can promote plant invasions, lead to invasional meltdown and inform management decisions." In Plant invasions: the role of biotic interactions, 153–76. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0153.

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Abstract In 1999, Daniel Simberloff and Betsy Von Holle introduced the term 'invasional meltdown'. The term and the concept have been embraced and critiqued but have taken a firm hold within the invasion biology canon. The original formulation of the concept argued two key points: first, biologists rarely study how non-natives interact with one another. Second, nearly all the conceptual models about the success and impact of invasive species are predicated on the importance of competitive interactions and an implicit assumption that non-natives should interfere with establishment, spread and impact of other non-natives. In response, Simberloff and Von Holle called for more research on invader interactions and proposed an alternative consequence of non-native species interactions - invasional meltdown - where facilitative interactions among non-natives could increase the invasion rate or ecological impacts in invaded systems. This chapter outlines the primary pathways in which direct and indirect interactions among non-natives could lead to invasional meltdown. It provides examples of how different types of interactions among non-natives could lead to net positive effects on the invasion success of non-native plants or the impact of non-native plants on invaded ecosystems. Direct effects are by far the most commonly explored form of non-native- non- native interaction, primarily focusing on plant mutualisms with pollinators, seed dispersers or soil microbial mutualists. There are, however, also examples of non-native plants that benefit from commensal and even herbivorous interactions with other non-natives. Indirect interactions among non-natives are very infrequently studied. Although examples are scarce, non-natives may indirectly benefit other non-native plants through trophic cascades, apparent competition and indirect mutualisms. It remains unclear whether indirect effects are important pathways to invasional meltdown. More work is needed on studying ecosystems that are invaded by multiple non-native species and we need to consider the full range of interactions among non-natives that could either stymie or promote their spread, population growth and impact. Only then can we address how common facilitative interactions are relative to competitive interactions among non-natives or provide robust suggestions on how to manage ecosystems.

Scholten, M., P. A. Blaauw, M. Stroetenga e J. Rozema. "The impact of competitive interactions on the growth and distribution of plant species in salt marshes". In Vegetation between land and sea, 270–83. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-4065-9_21.

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Atti di convegni sul tema "Competitive species":

ORTEGA, RAFAEL. "COMPETITIVE SYSTEMS WITH THREE SPECIES AND PERIODIC COEFFICIENTS". In Proceedings of the International Conference on Differential Equations. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812702067_0008.

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"Permanence for a N-species competitive system with feedback controls". In 2018 4th International Conference on Education, Management and Information Technology. Francis Academic Press, 2018. http://dx.doi.org/10.25236/icemit.2018.301.

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Zhang, Huayong, Tousheng Huang e Liming Dai. "Two New Competition Indexes on the Basis of Lotka-Volterra Competition Model". In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63250.

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In this research, two competition indexes, competing capacity and competing tensor, are brought forward to better understand the interspecific competition between species. With the employment of the two indexes, the competitive process in Lotka-Volterra model can be described much clearly. The strength of competition for a species is divided into three competition grades according to the competing tensor. In the interspecific competition, when two species are in different competition grades, the weak species will be excluded; when two species are in the same grade, the coexistent equilibrium will present. Two cases are studied with the methods by employing the two indexes. In the second case, the stability of equilibrium point is determined by the competing tensor. The new indexes have shown potential in population dynamics analysis.

Bargielowski, Irka E. "Satyrization and satyrization-resitance in competitive displacements of invasive mosquito species". In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.108796.

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Liao, Qingshui. "Permanence and almost periodic solution for a n-species competitive system". In 2018 4th International Conference on Economics, Social Science, Arts, Education and Management Engineering (ESSAEME 2018). Paris, France: Atlantis Press, 2018. http://dx.doi.org/10.2991/essaeme-18.2018.99.

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Wang, Xiaoyan, e Lingzhen Dong. "Analysis of a two-species stochastic competitive Lotka-Volterra system with dispersal". In 2016 3rd International Conference on Systems and Informatics (ICSAI). IEEE, 2016. http://dx.doi.org/10.1109/icsai.2016.7811026.

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Hemerik, Lia. "How competitive interactions between parasitoid species are shaped by herbivores, a model study". In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.110407.

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Vogel, Dayton. "Competitive Adsorption and Reactive Chemical Species Identification in RE-DOBDC MOFs via AIMD." In Proposed for presentation at the American Chemical Society National Spring Meeting 2021. US DOE, 2021. http://dx.doi.org/10.2172/1863693.

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Miao, Ji. "Exploring the Role of Plant Species Diversity in Drought Adaptation: Mathematical Modeling of Community Dynamics and Competitive Interactions". In ICMLCA 2023: 2023 4th International Conference on Machine Learning and Computer Application. New York, NY, USA: ACM, 2023. http://dx.doi.org/10.1145/3650215.3650320.

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Devarakonda, Maruthi, Russell Tonkyn, Diana Tran, Jong H. Lee e Darrell Herling. "Modeling Competitive Adsorption in Urea-SCR Catalysts for Effective Low Temperature NOx Control". In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39977.

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Although the SCR technology exhibits higher NOx reduction efficiency over a wider range of temperatures among the lean NOx reduction technologies, further improvement in low-temperature performance is required to meet the future emission standards and to lower the system cost. In order to improve the catalyst technologies and optimize the system performance, it is critical to understand the reaction mechanisms and catalyst behaviors with respect to operating conditions. For example, it is well known that the ammonia coverage on catalyst surface is critical for NOx reduction efficiency. However, the level of ammonia storage is influenced by competitive adsorption by other species, such as H2O and NO2. Moreover, hydrocarbon species that slip through the upstream DOC during the cold-start period can also inhibit the SCR performance, especially at low temperatures. Therefore, a one-dimensional kinetic model that can account for the effects of such competitive adsorption has been developed based on steady state surface isotherm tests on a commercial Fe-zeolite catalyst. The model is developed as a C language S-function and implemented in Matlab/Simulink environment. Rate kinetics of adsorption and desorption of each of the adsorbents are determined from individual adsorption tests and validated for a set of test conditions that had all the adsorbents in the feed gas. Using the competitive adsorption model, a kinetic model for standard-SCR reaction involving NH3 and H2O is developed and validated.

Rapporti di organizzazioni sul tema "Competitive species":

Harms, Nathan, e James Cronin. Phenology of competitive interactions and implications for management of the invasive wetland plant Alternanthera philoxeroides. Engineer Research and Development Center (U.S.), ottobre 2021. http://dx.doi.org/10.21079/11681/42188.

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Phenological differences between invading plants and members of recipient communities may increase the success of invaders because of priority effects. Thus, the application of management when the invader has a phenological advantage (for example, early in the year) can benefit other species by increasing resource availability. This technical note summarizes results from a combination of field observations and a mesocosm experiment to explore whether phenological differences between the invasive wetland plant, alligatorweed (Alternanthera philoxeroides [Mart.] Grseb.), and resident species contribute to alligatorweed success. We documented over two years the early-season growth of alligatorweed and other species at 12 sites in Louisiana, USA. We then conducted a subsequent mesocosm competition experiment between alligatorweed and a common wetland emergent species, spotted lady’s thumb (Persicaria maculosa [L.] Small), over a full year to detect differences in timing of growth and competitive interactions under two fertilizer levels.

Kapulnik, Yoram, e Donald A. Phillips. Isoflavonoid Regulation of Root Bacteria. United States Department of Agriculture, gennaio 1996. http://dx.doi.org/10.32747/1996.7570561.bard.

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The overall objective of this project was to develop a conceptual framework for enhancing root colonization by beneficial bacteria. To accomplish this aim we tested the hypothesis that production and excretion of the plant phytoalexin medicarpin can be used for creation of a special niche along the legume roots, where beneficial microorganism, such as rhizobium, will have a selective advantage. On the Israeli side it was shown that higher medicarpin levels are exuded following the application of Rhizobium meliloti to the rhizosphere but the specific biochemical pathway governing medicarpin production was not induced significantly enough to support a constant production and excretion of this molecule to the rhizosphere. Furthermore, pathogenic bacteria and chemical elicitors were found to induce higher levels of this phytoalexin and it became important to test its natural abundance in field grown plants. On the US side, the occurrence of flavonoids and nucleosides in agricultural soils has been evaluated and biologically significant quantities of these molecules were identified. A more virulent Agrobacterium tumefaciens strain was isolated from alfalfa (Medicago sativa L.) which forms tumors on a wide range of plant species. This isolate contains genes that increase competitive colonization abilities on roots by reducing the accumulation of alfalfa isoflavonoids in the bacterial cells. Following gene tagging efforts the US lab found that mutation in the bacterial efflux pump operons of this isolate reduced its competitive abilities. This results support our original hypothesis that detoxification activity of isoflavenoids molecules, based on bacterial gene(s), is an important selection mechanism in the rhizosphere. In addition, we focused on biotin as a regulatory element in the rhizosphere to support growth of some rhizosphere microorganisms and designed a bacterial gene construct carrying the biotin-binding protein, streptavidin. Expressing this gene in tobacco roots did not affect the biotin level but its expression in alfalfa was lethal. In conclusion, the collaborative combination of basic and applied approaches toward the understanding of rhizosphere activity yielded new knowledge related to the colonization of roots by beneficial microorganisms in the presence of biological active molecules exuded from the plant roots.

TABUNOV, I. A., A. P. LAPINA, M. M. KOSTYCHEV, P. S. BEREZINA e A. V. NIKIFOROVA. METHODOLOGICAL RECOMMENDATIONS FOR COACHES WORKING WITH CHILD ATHLETES ENGAGED IN ROCK CLIMBING. SIB-Expertise, dicembre 2022. http://dx.doi.org/10.12731/er0621.06122022.

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The methodological guide will present aspects that will be useful for coaches in working with their students, in particular psychological work with athletes during the training process and during the competition, and specifically in the pre-start period. It is important for the coach to teach the athlete the techniques of psychological protection, including restoring the stability control system, reducing feelings of anxiety and countering it. It is important to carry out special psychological training. Including effective preparation for competition, based on: social values; formation of mental "internal support"; overcoming psychological barriers. Every day the degree of development and influence of sports reaches a new level. Also, the requirements for athletes in technical, physical and tactical readiness are increasing, respectively, the result of competitive activity will already be determined by readiness and psychological attitude. Psychological preparation is a process aimed at creating a state of mental readiness for competition in athletes. This should be considered the subject of psychological preparation for competitions in sports.

Ashworth, William. Ecological interactions of habitat forming emergent vegetation : With focus on Phragmites australis and Typha sp. Department of Aquatic Resources, Swedish University of Agricultural Sciences, 2023. http://dx.doi.org/10.54612/a.7bt282v5l5.

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Stands of emergent vegetation such as the common reed (Phragmites australis) and members of the genus Typha are a key part of many freshwater and brackish shoreline ecosystems. Similar to trees in a forest, these macrophytes provide structural complexity, a source of food, and shelter from harsher abiotic conditions supporting a broad range of flora and fauna. However, in recent years, anthropogenic activities have facilitated these species to dominate their native ecosystems, forming increasingly homogenous reed beds, and furthermore to invade many non native habitats. In this text, I review the ecological interactions of habitat forming emergent vegetation with an emphasis on other macrophytes, fish, birds and invertebrates. Trends in literature highlight both the importance of emergent vegetation to aquatic ecosystems, but also the negative impact they can have when invading, or forming dense homogenous stands. The competitive exclusion of other macrophytes and physical reduction of space within stands of emergent vegetation are the main drivers that negate or reverse most of the beneficial ecological interactions of reed or Typha with other organisms. I also detail how various management practices have attempted to address the presented issues, with the most successful methods being those that aim to promote heterogeneity. While progress has been made, future studies should focus on the identification of optimal management practices, to pave the way for more effective conservation applications.

Grossman, Gene, e Elhanan Helpman. Electoral Competition and Special Interest Politics. Cambridge, MA: National Bureau of Economic Research, ottobre 1994. http://dx.doi.org/10.3386/w4877.

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Epiphan, Jean, e Steven Handel. Trajectory of forest vegetation under contrasting stressors over a 26-year period, at Morristown National Historical Park: Focused condition assessment report. National Park Service, marzo 2023. http://dx.doi.org/10.36967/2297281.

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The Jockey Hollow section and the New Jersey Brigade Area of Morristown National Historical Park (MORR) are predominantly comprised of upland oak-hickory forests that have regrown over the past 200 years from previous land uses. The forest is being damaged by two major stressors, a large population of white-tailed deer and an abundance of non-native, invasive shrubs and herbaceous species. This study explores changes to the forest over 26 years and suggests management techniques to avoid future degradation. The forest is typical of many upland stands in the region, and studies here would be applicable to many lands controlled by the National Park Service and to many public and private land owners. In 1995, 18 vegetation experimental plots were established in the forest, each 20 x 20 m. Ten plots were in areas that had no non-native, invasive plants. The other eight plots had invasive species. All trees, shrubs and a sampling of herbs were recorded in each of the 18 plots. At that time, no GPS technology was available and handwritten maps were used to record locations. The plots were revisited and resurveyed in 2001; however, only 13 plots were found. This 2021 study is a new survey of the plot conditions. The investigators were able to relocate 17 of the original plots. New GPS locations were recorded for these 17 plots to facilitate future studies. The goal of the study was to test if changes over 26 years in forest conditions differed between the original invaded plots as compared to the uninvaded plots. Also, these data will allow us to measure the progress of invasion into previously uninvaded areas. Together, these results will allow the forest managers to focus attention on the most aggressive plant invaders and to understand the fate of this forest type that is being challenged by deer and non-native plants. Over the last 26 years there has been no hunting for deer here. Also, the plots were not within the few deer exclosures at MORR; deer were able to enter the landscape from surrounding heavily wooded areas. Data were collected in four layers of vegetation – mature trees, saplings, shrubs, and herbaceous groundcovers. The mature trees in the invaded forest plots demonstrated declining trends. The species richness declined by 6%, the average number of trees declined by 30%, white ash and flowering dogwood had the most losses, and basal area did not increase over time because very few new saplings grew into mature tree sizes. The uninvaded plots’ mature trees also revealed a 20% declined in richness, number of trees declined by 18%, the greatest losses occurred for red maple and black birch, but basal area increased slightly due to growth of large persisting trees. Saplings in the invaded forest experienced declines over the 26 years. Species richness declined by 38%, number of native saplings decreased by 44%, and number of invasive saplings increased by 600%. In the uninvaded forest, the conditions and trends were variable. Richness decreased by 21%, no invasive saplings found, number of native saplings increased by 37% (due to increases in American beech). With American beech excluded, the number of native saplings decreased by 60%. In both forest types, the declining number of native saplings was primarily caused by excessive deer damage. For the shrub layer in invaded plots, Japanese barberry stems increased by 122% by 2001 and 276% by 2021. Barberry became the dominant species. Similarly, wineberry stands increased 486% in 2001 and 157% for 2021. It is now the second most common species. However, in the uninvaded plots there was no significant increase in the number of barberry stems and wineberry was not present in 1995 or 2001, and only averaged 1.5 stems per plot in 2021. Neither species has a significant presence now and eradication is possible. A major finding is that the process of invasion of these shrubs over 26 years is very slow. For the herbaceous plants, in the invaded plots there was a sharp decrease in cover by 2021 due to the competitive impact by the abundant invasive shrubs. The invasive Japanese stiltgrass declined 86% in cover and native Carex (sedge) species declined by 78%. In the uninvaded forest plots, stiltgrass was present in very low amounts and did not increase significantly over 26 years. The number of quadrats with any stiltgrass only increased from 3 to 5 over the 26 years. These data show that stiltgrass invades slowly in the uninvaded plots, but in the invaded plots it was greatly replaced by invasive shrubs. Overall, the rate of change of the native herb cover was slow. Together, these data suggest that currently uninvaded forest areas can be protected by monitoring and rigorously eliminating any initial invasions by non-native shrubs and herbs. Once these species reach a significant presence in number of stems or cover in a plot they explode in number. Early intervention when invasive plants first appear is the most practical management tool. Reduction of deer density will also increase the reproductive potential and sustainability of our main forest tree species. Planting of new young canopy tree species, with protection from deer, can retard the ability of invasive plants to begin new populations.

Levisohn, Sharon, Mark Jackwood e Stanley Kleven. New Approaches for Detection of Mycoplasma iowae Infection in Turkeys. United States Department of Agriculture, febbraio 1995. http://dx.doi.org/10.32747/1995.7612834.bard.

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Mycoplasma iowae (Mi) is a pathogenic avian mycoplasma which causes mortality in turkey embryos and as such has clinical and economic significance for the turkey breeder industry. Control of Mi infection is severely hampered by lack of adequate diagnostic tests, together with resistance to most antibiotics and resilience to environment. A markedly high degree of intra-species antigenic variation also contributes to difficulties in detection and control of infection. In this project we have designed an innovative gene-based diagnostic test based on specific amplification of the 16S rRNA gene of Mi. This reaction, designed Multi-species PCR-RFLP test, also amplifies the DNA of the pathogenic avian mycoplasmas M. gallisepticum (Mg) and M. synoviae (Ms). This test detects DNA equivalent to about 300 cfu Mi or either of the other two target mycoplasmas, individually or in mixed infection. It is a quick test, applicable to a wide variety of clinical samples, such as allantoic fluid or tracheal or cloacal swab suspensions. Differential diagnosis is carried out by gel electro-phoresis of the PCR amplicon digested with selected restriction enzymes (Restriction Fragment Length Polymorphism). This can also be readily accomplished by using a simple Dot-Blot hybridization assay with digoxigenin-labeled oligonucleotide probes reacting specifically with unique Mi, Mg or Ms sequences in the PCR amplicon. The PCR/OLIGO test increased sensitivity by at least 10-fold with a capacity for rapid testing of large numbers of samples. Experimental infection trials were carried out to evaluate the diagnostic tools and to study pathogenesis of Mi infection. Field studies and experimental infection of embryonated eggs indicated both synergistic and competitive interaction of mycoplasma pathogens in mixed infection. The value of the PCR diagnostic tests for following the time course of egg transmission was shown. A workable serological test (Dot Immunobinding Assay) was also developed but there was no clear-cut evidence that infected turkeys develop an immune response. Typing of a wide spectrum of Mi field isolates by a variety of gene-based molecular techniques indicated a higher degree of genetic homogeneity than predicted on the basis of the phenotypic variability. All known strains of Mi were detected by the method developed. Together with an M. meleagridis-PCR test based on the same gene, the Multi-species PCR test is a highly valuable tool for diagnosis of pathogenic mycoplasmas in single or mixed infection. The further application of this rapid and specific test as a part of Mi and overall mycoplasma control programs will be dependent on developments in the turkey industry.

Landau, Sergei Yan, John W. Walker, Avi Perevolotsky, Eugene D. Ungar, Butch Taylor e Daniel Waldron. Goats for maximal efficacy of brush control. United States Department of Agriculture, marzo 2008. http://dx.doi.org/10.32747/2008.7587731.bard.

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Background. Brush encroachment constitutes a serious problem in both Texas and Israel. We addressed the issue of efficacy of livestock herbivory - in the form of goat browsing - to change the ecological balance to the detriment of the shrub vegetation. Shrub consumption by goats is kept low by plant chemical defenses such as tannins and terpenes. Scientists at TAES and ARO have developed an innovative, cost-effective methodology using fecal Near Infrared Spectrometry to elucidate the dietary percentage of targeted, browse species (terpene-richredberry and blueberry juniper in the US, and tannin-rich Pistacialentiscus in Israel) for a large number of animals. The original research objectives of this project were: 1. to clarify the relative preference of goat breeds and the individual variation of goats within breeds, when consuming targeted brush species; 2. to assess the heritability of browse intake and validate the concept of breeding goat lines that exhibit high preference for chemically defended brush, using juniper as a model; 3. to clarify the relative contributions of genetics and learning on the preference for target species; 4. to identify mechanisms that are associated with greater intake of brush from the two target species; 5. to establish when the target species are the most vulnerable to grazing. (Issue no.5 was addressed only partly.) Major conclusions, solutions, achievements: Both the Israel and US scientists put significant efforts into improving and validating the technique of Fecal NIRS for predicting the botanical composition of goat diets. Israeli scientists validated the use of observational data for calibrating fecal NIRS, while US scientists established that calibrations could be used across animals differing in breed and age but that caution should be used in making comparisons between different sexes. These findings are important because the ability to select goat breeds or individuals within a breed for maximal efficiency of brush control is dependent upon accurate measurement of the botanical composition of the diet. In Israel it was found that Damascus goats consume diets more than twice richer in P. lentiscus than Mamber or Boer goats. In the US no differences were found between Angora and Boer cross goats but significant differences were found between individuals within breeds in juniper dietary percentage. In both countries, intervention strategies were found that further increased the consumption of the chemically defended plant. In Israel feeding polyethylene glycol (PEG, MW 4,000) that forms high-affinity complexes with tannins increased P. lentiscus dietary percentage an average of 7 percentage units. In the US feeding a protein supplement, which enhances rates of P450-catalyzed oxidations and therefore the rate of oxidation of monoterpenes, increased juniper consumption 5 percentage units. However, the effects of these interventions were not as large as breed or individual animal effects. Also, in a wide array of competitive tannin-binding assays in Israel with trypsin, salivary proteins did not bind more tannic acid or quebracho tannin than non-specific bovine serum albumin, parotid saliva did not bind more tannins than mixed saliva, no response of tannin-binding was found to levels of dietary tannins, and the breed effect was of minor importance, if any. These fundings strongly suggest that salivary proteins are not the first line of defense from tannin astringency in goats. In the US relatively low values for heritability and repeatability for juniper consumption were found (13% and 30%, respectively), possibly resulting from sampling error or non-genetic transfer of foraging behavior, i.e., social learning. Both alternatives seem to be true as significant variation between sequential observations were noted on the same animal and cross fostering studies conducted in Israel demonstrated that kids raised by Mamber goats showed lower propensity to consume P. lentiscus than counterparts raised by Damascus goats.

Brunkalla, Roberta. Influence of Mixing and Buoyancy on Competition Between Cyanobacteria Species in Upper Klamath Lake. Portland State University Library, gennaio 2000. http://dx.doi.org/10.15760/etd.5882.

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Elizur, Abigail, Amir Sagi, Gideon Hulata, Clive Jones e Wayne Knibb. Improving Crustacean Aquaculture Production Efficiencies through Development of Monosex Populations Using Endocrine and Molecular Manipulations. United States Department of Agriculture, giugno 2010. http://dx.doi.org/10.32747/2010.7613890.bard.

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Background Most of Australian prawn aquaculture production is based on P. monodon. However, the Australian industry is under intense competition from lower priced overseas imports. The availability of all-female monosex populations, by virtue of their large size and associated premium prize, will offer competitive advantage to the industry which desperately needs to counteract competitors within this market. As for the redclaw production in Israel, although it is at its infancy, the growers realized that the production of males is extremely advantageous and that such management strategy will change the economic assumptions and performances of this aquaculture to attract many more growers. Original objectives (as in original proposal) Investigating the sex inheritance mechanism in the tiger prawn. Identification of genes expressed uniquely in the androgenic gland (AG) of prawns and crayfish. The above genes and/or their products will be used to localize the AG in the prawn and manipulate the AG activity in both species. Production of monosex populations through AG manipulation. In the prawn, production of all-female populations and in the crayfish, all-male populations. Achievements In the crayfish, the AG cDNA library was further screened and a third AG specific transcript, designated Cq-AG3, had been identified. Simultaneously the two AG specific genes, which were previously identified, were further characterized. Tissue specificity of one of those genes, termed Cq-AG2, was demonstrated by northern blot hybridization and RNA in-situ hybridization. Bioinformatics prediction, which suggested a 42 amino acid long signal anchor at the N-terminus of the deduced Cq-AG2, was confirmed by immunolocalization of a recombinant protein. Cq-IAG's functionality was demonstrated by dsRNA in-vivo injections to intersex crayfish. Cq-IAGsilencing induced dramatic sex-related alterations, including male feature feminization, reduced sperm production, extensive testicular apoptosis, induction of the vitellogeningene expression and accumulation of yolk proteins in the ovaries. In the prawn, the AG was identified and a cDNA library was created. The putative P. monodonAG hormone encoding gene (Pm-IAG) was identified, isolated and characterized for time of expression and histological localization. Implantation of the AG into prawn post larvae (PL) and juveniles resulted in phenotypic transformation which included the appearance of appendix masculina and enlarged petasma. The transformation however did not result in sex change or the creation of neo males thus the population genetics stage to be executed with Prof. Hulata did not materialized. Repeated AG implantation is currently being trialed. Major conclusions and Implications, both scientific and agricultural Cq-IAG's involvement in male sexual differentiation had been demonstrated and it is strongly suggested that this gene encodes an AG hormone in this crayfish. A thorough screening of the AG cDNA library shows Cq-IAG is the prominent transcript within the library. However, the identification of two additional transcripts hints that Cq-IAG is not the only gene mediating the AG effects. The successful gene silencing of Cq-IAG, if performed at earlier developmental stages, might accomplish full and functional sex reversal which will enable the production of all-male crayfish populations. Pm-IAG is likely to play a similar role in prawns. It is possible that repeated administration of the AG into prawn will lead to the desired full sex reversal, so that WZ neo males, crossed with WZ females can result in WW females, which will form the basis for monosex all-female population.