Search results for "Competition"
showing 10 items of 1409 documents
Analysis and modeling of the role of nitrogen competition in weed control
2020
This project challenges the question of reducing herbicide use, considering that a concomitant reduction of nitrogen fertiliser use and a better choice of the sown species/varieties can help to design more sustainable cropping systems. Combining plant ecophysiology, ecology, agronomy and modelling, this project aims at analysing to which extent optimizing nitrogen fertilisation and crop species/cultivar choice can provide new ways to promote biological weed regulation via plant-plant competition, thereby reducing herbicide use. This project will use an original approach consisting in feeding and then using a mechanistic model, FLORSYS, predicting cropweed community assembly as a function of…
Stochastic model for a biological complex system: analysis of the bacterial growth in food products
2012
The Physics of Complex Systems has recently taken a more and more important role in the description of natural systems because of the interactions, both deterministic and noisy, between such systems and the environment. In particular the noise plays a relevant role in biological systems, whose dynamics is strongly influenced by environmental variables subject to random fluctuations. In this work a stochastic model is exploited to reproduce the growth of bacteria in food of animal origin. Specifically the dynamics of a bacterial species, Listeria monocytogenes, is analyzed in the presence of lactic acid bacteria (LAB) during the period of the fermentation of meat products. The model, based o…
Toward Value Co-Creation: Increasing Women’s Presence in Management Positions through Competition against a Set Target
2017
Despite empirical evidence that women’s presence in management positions is a source of value co-creation for firms, these positions are still male-dominated. Some evidence from experimental economics suggests that one reason for this imbalance is that women shy away from competition. However, most of these studies have focused on competition systems that pit individuals against each other. We present an economic laboratory experiment that compares competition against others with competition against a set target. The crucial difference is that whereas the former involves competing against opponents, the latter does not. Our results show that significantly more women are willing to compete a…
A quantitative assessment of intraspecific morphological variation in Gahagan bifaces from the southern Caddo area and central Texas
2019
This investigation aggregates intact or reconstructed Gahagan bifaces from the southern Caddo area and central Texas to test the hypothesis that Gahagan biface morphology differs between the regions. The Gahagan bifaces (n = 102) were scanned, then analysed using a novel landmarking protocol and the tools of geometric morphometrics. Results provide a preview of the significant differences in Gahagan biface morphology expressed between the southern Caddo area and central Texas regions. The size discrepancy represents an inversion of current theoretical constructs that posit a decrease in tool size thought to articulate with an increase in distance from the raw material source. It is posited …
Factors Affecting Interspecific Aggression in a Year-Round Territorial Species, the Jewel Damselfish
2012
Vertebrates live in complex species networks in which interspecific interactions are common. In some contexts, the aggressive behaviours shown in these interspecific interactions are very similar to those shown in intraspecific interactions. It is still an open question whether intra- and interspecific aggression share common causality. We studied a year-round territorial species the jewel damselfish, (Plectroglyphidodon lacrymatus), which cultivate algae they feed on. Territory holders aggressively defend these algae that are an attractive resource for many other species. In this study, we recorded territorial aggression in free-living individuals and recorded aggressive responses to a sta…
Can large branchiopods shape microcrustacean communities in Mediterranean temporary wetlands?
2011
It was recently suggested that large branchiopods may play a keystone role in temporary aquatic habitats. Using a microcosm experiment manipulating microcrustacean communities of Mediterranean temporary wetlands (Camargue, Southern France), we tested the following hypotheses: (i) large branchiopods (the notostracan Triops cancriformis and the anostracan Chirocephalus diaphanus) can limit microcrustacean densities through both competition and predation; (ii) notostracans create high suspended-matter concentrations through bioturbation, which can negatively impact microcrustaceans; and (iii) the outcome of these biotic interactions is more detrimental at high salinities. We found a strong pr…
Sex-specific transgenerational effects of early developmental conditions in a passerine
2007
Most studies dealing with the trade-off between offspring number and quality have overlooked the long-term consequences for the progeny. High investment in offspring number usually results in an increased competition among nest mates. The deterioration of the early developmental conditions, due to this increased competition, can impair individual quality over the long term, and subsequently affect survival and lifetime fecundity. Moreover, the consequences of the allocation rule to offspring number vs. quality can extend across generations and give raise to grandparental effects. These transgenerational trade-offs have been explored rarely. In the present study, we manipulated the breeding …
Behavioural responses of Eurasian treecreepers, Certhia familiaris, to competition with ants
1997
Competition for a specific resource that is essential for the survival of both the competitors may be intense even between very dissimilar taxa. However, the importance of the effects caused by such interspecific competition has seldom been emphasized. These effects can appear as differences in individual foraging behaviour during the breeding season, which can result in critical variation in fitness. In this study we examined the effects of wood ants (Formica rufa group) on the abundance of other invertebrates on tree trunks and on the foraging site selection of breeding Eurasian treecreepers, which use the same habitat as wood ants. Arthropods were scarcer on the trunks with ants present;…
Intercohort competition causes spatial segregation in brown trout in artificial streams
1999
When together in a flume, 13-cm LS (age-1) trout appeared to increase their activity and behaved more aggressively, whereas 10-cm LS (age-0) trout tended to move less and were rarely aggressive in the presence of the larger size class. Both size classes were less mobile and preferred lower water velocities in winter than in summer, and increased their use of instream cover in winter. When both size classes were present, only small trout decreased their use of low water velocities and cover. The results indicate that intercohort competition may cause spatial segregation among size groups of brown trout, especially in winter when trout attempt to minimize their maintenance costs.
Exploitation competition between hole‐nesters ( Muscardinus avellanarius , Mammalia and Parus caeruleus , Aves) in Mediterranean woodlands
2005
Data from a long-term study (1993-2003) using artificial nest-boxes, were analysed to examine competition for nesting between blue tit Parus caeruleus and common dormouse Muscardinus avellanarius in Sicily. Occupation rates and the reproductive biology of the blue tit in sample woodlots outside the distribution area of the common dormouse were used as a control in sample areas where the two species were syntopic. A selection test showed that the two species, when living in syntopy, actively chose the small nest-boxes, thus overlapping in the use of the same spatial resource. The experimental exclusion of the common dormouse from nest-boxes caused an increase of blue tit occupation rate. Onc…