Experimental tests of intercohort competition for food and cover in the tidepool sculpin (Oligocottus maculosus Girard)

2002 ◽  
Vol 80 (1) ◽  
pp. 137-144 ◽  
Author(s):  
Andrew R Szabo
Keyword(s):  
Competitive Advantage ◽  
Standard Length ◽  
Competitive Ability ◽  
Experimental Tests ◽  
Size Difference ◽  
Laboratory Setting ◽  
Aggressive Interactions ◽  
Competition For Food ◽  
Log Linear ◽  
Oligocottus Maculosus

In the field, the tidepool sculpin, Oligocottus maculosus, has been observed to display a vertical intertidal distribution characterized by increasing mean standard length with decreasing distance above mean tidal height. It was hypothesized that this distribution is related to intercohort competition for food and (or) cover and, as a result, competi tive exclusion of smaller fish by larger fish from the lower pools. To test this hypothesis, several competition experiments were conducted that involved pairing O. maculosus from three size classes in a laboratory setting and observing their behaviour when presented with food or cover. When both fish attempted to procure food, the success rate of the larger fish was significantly higher than that of the smaller fish (Wilcoxon's signed-ranks test, T = 0, N = 6, p < 0.025). Furthermore, as the size difference between the two fish increased, the smaller fish made significantly fewer simultaneous attempts to procure the food (hierarchical log-linear test, partial χ2[5] = 28.326, p < 0.001), and utilized the cover significantly less (ANOVA, F[5] = 3.387, p = 0.008). The results from these experiments indicated that larger fish have a competitive advantage over smaller fish which extends to the acquisition of both food and cover. This is presumed to be the result of both greater competitive ability due to increasing size and an increased need for smaller fish to avoid detrimental aggressive interactions. In view of evidence from other papers indicating that the lower pools are more desirable to O. maculosus, it is suggested that intercohort competition is in part responsible for limiting the smaller fish to the upper tide pools.

scholarly journals Influence of preemergently applied herbicides on the yield and quality of caraway achenes (Carum carvi L.)

2008 ◽  
Vol 56 (2) ◽  
pp. 255-266
Author(s):  
Antonín Vaculík
Keyword(s):  
Essential Oil ◽  
Standard Length ◽  
Oil Content ◽  
Competitive Ability ◽  
Weed Species ◽  
Yield And Quality ◽  
Significant Difference ◽  
Positive Effect ◽  
Different Doses

Caraway has very low competitive ability against most of weed species. Therefore, it is important to choose a suitable herbicide control, especially at biennial caraway. The experiments with the herbicides applied in caraway were found in pure growth, with variety Kepron (with standard length of ve­ge­ta­ti­ve period). The aim of the trials was to find out the differences at achenes yiled and essential oil content after the treatment by the various herbicides, applied preemergently. Also, the selective ac­ti­vi­ty of individual herbicides was tested, including the different doses. The herbicides used in the ex­pe­ri­ments had enough level of selektivity on the plants of caraway. They had a positive effect on the yiled comparing to non-treated control variant in all observed years. There was no statistically significant difference in essential oil kontent between the treated variants and non-treated control. On the basis of these results, the most suitable herbicide was chosen for the „minor“ registration for caraway.

scholarly journals Negative Fitness Consequences and Transmission Dynamics of a Heritable Fungal Symbiont of a Parasitic Wasp

2009 ◽  
Vol 75 (10) ◽  
pp. 3115-3119 ◽  
Author(s):  
Cara M. Gibson ◽  
Martha S. Hunter
Keyword(s):  
Competitive Ability ◽  
Horizontal Transmission ◽  
Parasitic Wasp ◽  
Experimental Tests ◽  
Bacterial Symbionts ◽  
Fitness Costs ◽  
Fungal Symbiont ◽  
Fitness Consequences ◽  
Single Host ◽  
Host Ecology

ABSTRACT Heritable bacterial symbionts are widespread in insects and can have many important effects on host ecology and fitness. Fungal symbionts are also important in shaping their hosts' behavior, interactions, and evolution, but they have been largely overlooked. Experimental tests to determine the relevance of fungal symbionts to their insect hosts are currently extremely rare, and to our knowledge, there have been no such tests for strictly predacious insects. We investigated the fitness consequences for a parasitic wasp (Comperia merceti) of an inherited fungal symbiont in the Saccharomycotina (Ascomycota) that was long presumed to be a mutualist. In comparisons of wasp lines with and without this symbiont, we found no evidence of mutualism. Instead, there were significant fitness costs to the wasps in the presence of the yeast; infected wasps attacked fewer hosts and had longer development times. We also examined the relative competitive abilities of the larval progeny of infected and uninfected mothers, as well as horizontal transmission of the fungal symbiont among larval wasps that shared a single host cockroach egg case. We found no difference in larval competitive ability when larvae whose infection status differed shared a single host. We did find high rates of horizontal transmission of the fungus, and we suggest that this transmission is likely responsible for the maintenance of this infection in wasp populations.

Western white pine growth relative to forest openings

2004 ◽  
Vol 34 (11) ◽  
pp. 2187-2198 ◽  
Author(s):  
Theresa B Jain ◽  
Russell T Graham ◽  
Penelope Morgan
Keyword(s):  
Competitive Advantage ◽  
Polynomial Regression ◽  
Timber Harvesting ◽  
Tree Age ◽  
Pinus Monticola ◽  
White Pine ◽  
Canopy Opening ◽  
Western White Pine ◽  
Sapling Growth ◽  
Log Linear

In northern Rocky Mountains moist forests, timber harvesting, fire exclusion, and an introduced stem disease have contributed to the decline in western white pine (Pinus monticola Dougl. ex D. Don) abundance (from 90% to 10% of the area). Relations between canopy openings (0.1–15 ha) and western white pine growth within different physical settings are identified. Objectives include relating western white pine seedling and sapling growth to canopy opening attributes (defined by fisheye photography), identifying western white pine competitive thresholds (occupancy, competitive advantage, free-to-grow status) in relation to opening size, and relating canopy opening attributes to overstory density descriptors. We sampled 620 western white pine plus competing trees, canopy opening characteristics, landscape position, and overstory density descriptors. Analysis included log-linear and polynomial regression. Visible sky (canopy opening) and tree age were significantly related to growth of selected pines. Radiation explained less variation in growth than canopy opening. Thresholds for western white pine to occupy a site (>23% canopy opening), gain a competitive advantage (>50% canopy opening), and achieve free-to-grow status (>92% canopy opening) over western hemlock were developed. There was a significant although weak (R2 < 0.12) relation between canopy opening and overstory density descriptors.

The use of nitrogen, phosphorus and lime to limit the competitive ability of Aristida armata in the establishment phase

1993 ◽  
Vol 44 (1) ◽  
pp. 165 ◽  
Author(s):  
RD Armstrong ◽  
RF Brown ◽  
KR Helyar
Keyword(s):  
Competitive Advantage ◽  
Competitive Ability ◽  
Cenchrus Ciliaris ◽  
Replacement Series ◽  
Red Earth ◽  
Competitive Species ◽  
Per Se ◽  
Grazing Lands ◽  
Establishment Phase ◽  
Nitrogen Phosphorus

The de Wit replacement series methodology was used to see if applying phosphorus, nitrogen and lime to the sandy red earth soils of mulga grazing lands can give a competitive advantage to the desirable species Cenchrus ciliaris C.V. U.S.A., Digitaria ammophila, and Thyridolepis mitchelliana over the less desirable Aristida armata. In monoculture, all species responded strongly to added nutrients, especially phosphorus. In mixtures, the preferred grasses responded even more strongly to nutrients, whereas A. armata responsed proportionally less. C. ciliaris, D. ammophila, and T. mitchelliana suppressed the growth of A. amnata in all but three situations: without added nutrients, A. armata was equally competitive with C. ciliaris; when P was added without lime, A. armata suppressed C. ciliaris; if P was added without N, A. armata suppressed T. mitchelliana. Adding either or both nitrogen or phosphorus usually increased the relative crowding coefficients, indicating that the degree of suppression of Aristida was increased by adding nutrients. Thus, C. ciliaris, D. ammophila, and T. mitchelliana appear to be equally competitive with or more competitive than A. armata if the soil is not fertilized and adding nutrients generally enhances this competitiveness. In all cases, except for A. armata/C ciliaris mixtures in soils low in phosphorus, the plants appeared to be competing for the same resource. The study demonstrated that A. armata is not a highly competitive species per se under controlled conditions and was generally suppressed by the preferred grasses, especially when nutrients were added.

scholarly journals Wake up and smell the conflict: odour signals in female competition

2013 ◽  
Vol 368 (1631) ◽  
pp. 20130082 ◽  
Author(s):  
Paula Stockley ◽  
Lisa Bottell ◽  
Jane L. Hurst
Keyword(s):  
Competitive Ability ◽  
Scent Marking ◽  
House Mice ◽  
Scent Mark ◽  
Female Competition ◽  
Scent Marks ◽  
Natural Conditions ◽  
Major Urinary Protein ◽  
Aggressive Interactions ◽  
Female Ornaments

Odour signals used in competitive and aggressive interactions between males are well studied in the context of sexual selection. By contrast, relatively little is known about comparable signals used by females, despite current interest in the evolution of female ornaments and weaponry. Available evidence suggests that odour signals are important in competitive interactions between female mammals, with reductions or reversals of male-biased sexual dimorphism in signalling where female competition is intense. Scent marking is often associated with conflict between females over access to resources or reproductive opportunities. Female scent marks may therefore provide reliable signals of competitive ability that could be used both by competitors and potential mates. Consistent with this hypothesis, we report that aggressive behaviour of female house mice is correlated with the amount of major urinary protein (MUP) excreted in their urine, a polymorphic set of proteins that are used in scent mark signalling. Under semi-natural conditions, females with high MUP output are more likely to produce offspring sired by males that have high reproductive success, and less likely to produce offspring by multiple different sires, suggesting that females with strong MUP signals are monopolized by males of particularly high quality. We conclude that odour signals are worthy of more detailed investigation as mediators of female competition.

scholarly journals The Slovak Republic Regional Development through Cluster Iniciative

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
V. Littvova
Keyword(s):  
Competitive Advantage ◽  
Regional Development ◽  
Competitive Ability ◽  
Slovak Republic ◽  
Cluster Formation ◽  
Global Changes ◽  
Business Activity ◽  
Market Environment ◽  
Innovative Solutions ◽  
Young Entrepreneurs

Abstract The current market environment is defined by constant financial and global changes. For companies operating in market business activities it has been increasingly difficult to adapt and remain competitive in such environment. In accordance with the exclusive survey among young entrepreneurs, one in four of them starts their business without training and about a one third has no idea how to get to the customers. Constant financial and global changes cause that existing organizations realizing business activity adapt and remain competitive ability with increasing difficulties. Several organizations, as self-employed units are not able to cope with handicaps or use the positives that globalization brings on the world's markets. The process of globalization requires highly flexible receiving of innovative solutions which often especially SMEs are not able to carry out. One of the possible strategies which organization can receive to maintain its competitive advantage is the “cluster” formation.

scholarly journals LAJU PERTUMBUHAN DAN ANALISA DAYA SAING EKSPOR UNGGULAN DI PROPINSI KALIMANTAN SELATAN

2010 ◽  
Vol 8 (2) ◽  
pp. 327
Author(s):  
. Safriansyah
Keyword(s):  
Growth Rate ◽  
Data Analysis ◽  
Competitive Advantage ◽  
Growth Analysis ◽  
Competitive Ability ◽  
Average Rate ◽  
Export Growth ◽  
Export Product ◽  
Average Index

The objective of this research is to knoe the rate of export growth and the competitive ability of superior export commodity in south kalimantan in 2003-2007. In order to know the growth rate of superior export product in south kalimantan, the researcher used growth analysis, while to analyze the rate of competitive ability of export commodity in south kalimantan, the researcher used Revealed Competitive Advantage (RCA), Revealed Comparative Trade Advantage (RCTA) and Indeks Spesialisasi Perdagangan (ISP) analysis. Based on the research and data analysis, it is known that since 2003 until 2007, the export growth in south kalimantan has always been increasing. The average rate of export in south kalimantan is 25,4% since 2003 until 2007. While the hogest average rate of superior export product is 150, 01% for rubber product.While the lowest average rate is -3,06% for Rotan. The level of export competitive abilty, mining product has the higest RCA index, 6,78 since 2003 until 2007. And the lowest average index is 6,18 for logging product. By using RCTA analysis, the higest average index is 24,89 for mining product since 2003 until 2007. In ISP analysis, the higest average index is 0,99 for mining, while the lowest is 0,44 for Rotan product since 2003-2007.

scholarly journals Study on Resource Allocations for Sustainable Competitive Advantage

2013 ◽  
Vol 4 (3) ◽  
pp. 65-75 ◽  
Author(s):  
Josu Takala ◽  
Daryna Shylina ◽  
Teppo Forss ◽  
Johannes Malmi
Keyword(s):  
Competitive Advantage ◽  
Competitive Ability ◽  
Business Environment ◽  
Competitive Advantages ◽  
Sustainable Competitive Advantage ◽  
Global Business ◽  
Analytical Hierarchical Process ◽  
Critical Areas ◽  
Sense And Respond ◽  
Unpredictable Environment

Abstract Today’s concern and problem for most of the companies is the way of surviving and prospering in current and future periods of time in the marketplace. Sustainable competitive ability can be one of the ways of adaptation to the global business and rapid environment requirements. Operational competitiveness is not easy to be sustainably improved because of unpredictable environment situations, such as continuous increasing customer needs, global competitive environment, rapid and unpredictable changes in government policy, company crisis during significant changes etc. However, it is possible to make adaptive adjustments on operations strategy level in dynamic business environment and to become competitive enough compared to the competitors. The purpose of this paper is to define and assess sustainable competitive advantage and the direction of development in housing business. It can be analysed by two core factors, i.e. Sense and Respond (S&R) methodology, Analytical Hierarchical Process (AHP) as well as Sustainable competitive advantage (SCA) method. This study also focuses on applying S&R method in order to optimize operational competitiveness as well as defining the competitive priorities of the case company. The analysis results show the critical areas in different departments of the case company, which can help the managers to make quick decisions. In addition, they reveal that during the crisis the resource allocation is continuously changing and therefore the operation strategy of the case company is not well defined as well as competitive advantages are not enough sustainable

scholarly journals Competitive Ability of Capsicum annuum L. Relative to the Weed Amaranthus lividus L.

2016 ◽  
Vol 24 (1) ◽  
pp. 79-91 ◽  
Author(s):  
Abdessatar Omezine ◽  
Jaime A. Teixeira da Silva
Keyword(s):  
Competitive Advantage ◽  
Capsicum Annuum ◽  
Competitive Ability ◽  
Relative Yield ◽  
Biomass Accumulation ◽  
Dry Weight ◽  
Lower Proportion ◽  
The Other ◽  
Yield Analysis ◽  
Replacement Experiment

AbstractAmaranthus lividusis the most frequently reported troublesome weed in the production ofCapsicum annuumin some regions because it is an aggressive invader, difficult to control, and reduces yield significantly. The effects ofA.lividuson the growth ofC.annuum‘Baklouti’ were evaluated under greenhouse conditions. Three experiments were conducted to determine the effect ofA.lividuson the biomass accumulation ofC.annuumseedlings for 40 days. In an additive experiment, to oneC.annuumseedling and 1, 2, 3 or 4A.lividusseedlings were grown per pot. The second experiment was established to assessC. annuumintracompetition using from one to six plants per pot as the density. In a replacement experiment,C.annuumandA.lividusseedlings were transplanted into pots with different proportions of both plants (1/5, 2/4, 3/3, 4/2, 5/1). Competition byA.lividusreducedC.annuumplant dry weight by as much as 93%. However,C.annuumhad little effect onA.lividus, reducing dry weight by 31.3% at a 5:1 ratio ofC.annuum:A.lividus. Relative yield analysis betweenC. annuumandA. lividusdemonstrated the competitive advantage ofC. annuumoverA. lividus.The relative crowding coefficient of both plants changed significantly in the presence of the other plant, at any ratio. The aggressivity ofC.annuumwas higher at its lower proportion andC.annuumwas more aggressive towards itself than towardsA.lividuswhen its density increased.

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