Search results for " Allocation"
showing 10 items of 502 documents
Sex-specific responses to cold in a very cold-tolerant, northern Drosophila species
2021
Funding: This work was supported by Academy of Finland projects 268214 and 322980 to MK and a NERC (UK) grant NE/P000592/1 to MGR. Organisms can plastically alter resource allocation in response to changing environmental factors. For example, in harsh conditions, organisms are expected to shift investment from reproduction toward survival; however, the factors and mechanisms that govern the magnitude of such shifts are relatively poorly studied. Here we compared the impact of cold on males and females of the highly cold-tolerant species Drosophila montana at the phenotypic and transcriptomic levels. Although both sexes showed similar changes in cold tolerance and gene expression in response…
Sex Allocation Theory for Facultatively Sexual Organisms Inhabiting Seasonal Environments: The Importance of Bet Hedging
2018
Adaptive explanations for dormancy often invoke bet hedging, where reduced mean fitness can be adaptive if it associates with reduced fitness variance. Sex allocation theory typically ignores variance effects and focuses on mean fitness. For many cyclical parthenogens, these themes become linked, as only sexually produced eggs undergo the dormancy needed to survive harsh conditions. We ask how sex allocation and the timing of sex evolve when this constraint exists in the form of a trade-off between asexual reproduction and sexual production of dormant eggs-the former being crucial for within-season success and the latter for survival across seasons. We show that male production can be tempo…
Daphnia females adjust sex allocation in response to current sex ratio and density
2018
Cyclical parthenogenesis presents an interesting challenge for the study of sex allocation, as individuals’ allocation decisions involve both the choice between sexual and asexual reproduction, and the choice between sons and daughters. Male production is therefore expected to depend on ecological and evolutionary drivers of overall investment in sex, and those influencing male reproductive value during sexual periods. We manipulated experimental populations, and made repeated observations of natural populations over their growing season, to disentangle effects of population density and the timing of sex from effects of adult sex ratio on sex allocation in cyclically parthenogenetic Daphnia…
State-dependent pairing behaviour in male Gammarus pulex (L.) (Crustacea, Amphipoda): effects of time left to moult and prior pairing status
2004
Because mating can be costly in terms of time and energy, an individual's propensity to engage in courtship and mating activities might be modulated by its physiological state. However, so far, state-dependent mate choice has received little attention The present study examined the effect of both prior pairing status and time left to the moult on the ability of male Gammarus pulex (Crustacea, Amphipoda) to enter in precopula with receptive females. In the lab, males that were freshly collected in precopula pairs in the field had a higher probability of re-pairing and were quicker to enter in precopula with receptive females compared to males of similar size that were freshly collected unpai…
Food provisioning alters infection dynamics in populations of a wild rodent
2015
While pathogens are often assumed to limit the growth of wildlife populations, experimental evidence for their effects is rare. A lack of food resources has been suggested to enhance the negative effects of pathogen infection on host populations, but this theory has received little investigation. We conducted a replicated two-factor enclosure experiment, with introduction of the bacteriumBordetella bronchisepticaand food supplementation, to evaluate the individual and interactive effects of pathogen infection and food availability on vole populations during a boreal winter. We show that prior to bacteria introduction, vole populations were limited by food availability.Bordetella bronchisept…
Intraspecific competition affects population size and resource allocation in an ant dispersing by colony fission
2010
Intraspecific competition is a pervasive phenomenon with important ecological and evolutionary consequences, yet its effect in natural populations remains controversial. Although numerous studies suggest that in many cases populations across all organisms are limited by density-dependent processes, this conclusion often relies on correlative data. Here, using an experimental approach, we examined the effect of intraspecific competition on population regulation of the ant Aphaenogaster senilis. In this species females are philopatric while males disperse by flying over relatively long distances. All colonies were removed from 15 experimental plots, except for one focal colony in each plot, w…
Identifying a key host in an acanthocephalan-amphipod system.
2015
SUMMARYTrophically transmitted parasites may use multiple intermediate hosts, some of which may be ‘key-hosts’, i.e. contributing significantly more to the completion of the parasite life cycle, while others may be ‘sink hosts’ with a poor contribution to parasite transmission. Gammarus fossarum and Gammarus roeseli are sympatric crustaceans used as intermediate hosts by the acanthocephalan Pomphorhynchus laevis. Gammarus roeseli suffers higher field prevalence and is less sensitive to parasite behavioural manipulation and to predation by definitive hosts. However, no data are available on between-host differences in susceptibility to P. laevis infection, making it difficult to untangle the…
Neuroprotective action of diazepam at very low and moderate doses in Alzheimer's disease model rats
2018
Abstract Early manifestations of Alzheimer's disease (AD) include neuroinflammation, disrupted neurotransmission and cognitive deficits. Impairment of the GABAergic system is essentially involved in the pathogenesis of AD. Traditionally, agonists of GABAA receptors at doses above 1 mg/kg are known to possess memory impairing effects. However, we have previously found that GABAA receptor GABA site ligand muscimol at very low doses acted contrary – enhanced spatial learning/memory, as well as prevented neuroinflammation and augmented neurotransmission in AD model rats. Therefore, in the present study we focused on the assessment of the effects of non-sedative – very low (0.05 mg/kg) and moder…
Cognitive resource allocation determines the organization of personal networks
2018
Significance The way we organize our social relationships is key to understanding the structure of our society. We propose a quantitative theory to tackle this issue, assuming that our capacity to maintain relationships is limited and that different types of relationships require different investments. The theory accounts for well-documented empirical evidence on personal networks, such that connections are typically arranged in layers of increasing size and decreasing emotional content. More interestingly, it predicts that when the number of available relationships is small, this structure is inverted, having more close relationships than acquaintances. We provide evidence of the existence…
Efficacy of N-acetylcysteine in the prevention of alcohol relapse-like drinking: Study in long-term ethanol-experienced male rats
2021
Alcohol use disorders are chronic and highly relapsing disorders, thus alcoholic patients have a high rate of recidivism for drug use even after long periods of abstinence. The literature points to the potential usefulness of N-acetylcysteine (NAC) in the management of several substance use disorders probably due to its capacity to restore brain homeostasis of the glutamate system disrupted in addiction. However, there is little evidence in the case of alcohol. The aim of this study was to explore the potential anti-relapse efficacy of NAC using the alcohol deprivation effect (ADE) model in long-term experienced rats. Two experiments were performed in male Wistar rats to: (a) test the effic…