Search results for "Quotation"
showing 10 items of 18815 documents
Characterization of Fusarium oxysporum populations by growth parameter evaluation in microtiter plates
1997
Trophic competition for the C source is the main mechanism involved in the interaction between pathogenic and non-pathogenic populations of Fusarium oxysporum. Therefore, a phenotypical characterization based on the growth characteristics of these populations will provide classical genotypical characterizations with additionnal information of ecological significance.
An ecological multi-Level theory of competition for resources used to analyse density-dependence effects in fruit production
2014
International audience; Lescourret and Génard (2003) developed a multi-level theory of competition for resources applied to fruit production, considering that any collection of unit parts (cells or seeds in a fruit, fruits in an infructescence or in a tree...) can form a population and the population is subject to competition, whatever the level of organization. The principles of the theory are that the mass of each unit decreases when the number of units in the population increases and that the total mass of the population increases as the number of units increases until it reaches a maximum, after which it decreases. A three-parameter model based on that theory was used to analyse the lev…
Changes in body mass and hormone levels between wintering and spring staging areas in Dark-bellied brent geese Branta bernicla bernicla
2006
International audience; Wintering migratory geese generally replenish protein stores lost during migration before building up their fat stores (Gauthier et al. 1992). Dark-bellied brent geese Branta bernicla bernicla winter mainly along the coasts of France, England and the south-western part of the Netherlands, and stage from March till late May mainly in the Wadden Sea, stretching from the northern Netherlands to Denmark (Ebbinge et al. 1999). During spring, geese accumulate body stores needed both for their long-distance migration to the breeding grounds and for reproduction (Spaans et al. 1993, Ebbinge and Spaans 1995). Dark-bellied brent geese, migrating about 5000 km between the winte…
Reproductive monopoly enforced by sterile police workers in a queenless ant
2004
In societies of totipotent insects, dyadic dominance interactions generate a hierarchy that often underlies an extreme reproductive skew. Subordinates remain infertile but can maximize their indirect fitness benefits through collective power (worker policing): interference with challenging high-rankers can prevent an untimely replacement of the reproductive. However, police workers only benefit if they favor individuals with high fertility. In the monogynous queenless ant Streblognathus peetersi, we used behavioral, physiological, and chemical methods to show that police workers have the primary role in the selection of the reproductive, and that they probably use reliable information about…
Parasitoids flip a coin before deciding to superparasitize
2004
Summary 1. Host acceptance decision in parasitic wasps depends strongly on the parasitism status of the encountered host. In solitary species, a host allows the development of only a single parasitic larva, and then any oviposition in an already parasitized host leads to larval competition and to potential loss of offspring. The ability of parasitoids to discriminate between parasitized and healthy hosts is well documented. Despite this, parasitized hosts are still accepted by the foraging wasps, an occurrence termed superparasitism. 2. In the last decades, theoretical studies have suggested that under certain circumstances superparasitism can be optimal. Generally, the superparasitism theo…
Social dominance correlates and family status in wintering dark-bellied brent geese Branta bernicla bernicla
2006
International audience; In many gregarious species, including ducks and geese, being dominant provides more benefits than costs, because dominants have better access to resources essential for survival or reproduction. In geese, being in better body condition during migration towards the breeding grounds positively influences reproductive success. However, underlying proximate mechanisms linking prebreeding body condition on the wintering grounds to breeding success remain poorly understood. We investigated social dominance correlates and family status, in three consecutive winters, in a free-ranging, migrating, dark-bellied brent goose population. Families with juveniles dominated pairs, a…
Fruit size in relation to competition for resources: A common model shared by two species and several genotypes grown under contrasted carbohydrate l…
2012
International audience; Fruit size is one important criterion of fruit external quality affecting consumer acceptance. The effects of seed number on fruit size in two fleshy fruits, grape and tomato, of different genotypes and grown under distinct carbohydrate availability levels were analyzed with a model. The two-parameter model described within-fruit resource competition and was able to well represent the commonly observed decrease in fresh weight per seed along with the increase in number of seeds, regardless of species, genotypes, and carbohydrate levels that were evaluated in this study. However, carbohydrate levels largely modified the correlation between seed number and fresh weight…
Prospects of herbivore egg-killing plant defenses for sustainable crop protection
2016
Abstract Due to a growing demand of food production worldwide, new strategies are suggested to allow for sustainable production of food with minimal effects on natural resources. A promising alternative to the application of chemical pesticides is the implementation of crops resistant to insect pests. Plants produce compounds that are harmful to a wide range of attackers, including insect pests; thus, exploitation of their natural defense system can be the key for the development of pest‐resistant crops. Interestingly, some plants possess a unique first line of defense that eliminates the enemy before it becomes destructive: egg‐killing. Insect eggs can trigger (1) direct defenses, mostly i…
Experimental Introgression To Evaluate the Impact of Sex Specific Traits on Drosophila melanogaster Incipient Speciation
2019
AbstractSex specific traits are involved in speciation but it is difficult to determine whether their variation initiates or reinforces sexual isolation. In some insects, speciation depends of the rapid change of expression in desaturase genes coding for sex pheromones. Two closely related desaturase genes are involved in Drosophila melanogaster pheromonal communication: desat1 affects both the production and the reception of sex pheromones while desat2 is involved in their production in flies of Zimbabwe populations. There is a strong asymmetric sexual isolation between Zimbabwe populations and all other “Cosmopolitan” populations: Zimbabwe females rarely copulate with Cosmopolitan males w…
Boldness-exploration behavioral syndrome: interfamily variability and repeatability of personality traits in the young of the convict cichlid (Amatit…
2015
9 pages; International audience; In recent years, considerable research interest in behavioral ecology has focused on characterizing and understanding individual differences in behavior that are consistent over time and across contexts, termed animal “personalities,” and correlations between various behaviors across contexts, termed behavioral syndromes. Although there is some evidence that differences in personality among individuals within populations can be genetically based and adaptive, when and how individual personality differences emerge in a population is not well understood, but of considerable general interest. Here, using juveniles of the convict cichlid (Amatitlania siquia) as …