Loss of density-dependence and incomplete control by dominant breeders in a territorial species with density outbreaks

<p>Abstract</p> <p>Background</p> <p>A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression.</p> <p>Results</p> <p>We studied density dependence in an <it>arvicoline </it>species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density.</p> <p>Conclusions</p> <p>At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a <it>competition point</it>), the dominance of breeders could not be sustained (<it>incomplete control</it>). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.</p

The charging of neutral dimethylamine and dimethylamine-sulphuric acid clusters using protonated acetone

Peer reviewe

The charging of neutral dimethylamine and dimethylamine-sulphuric acid clusters using protonated acetone

Peer reviewe

Russia of Challenges

In 2007 the Ministry of Defence conducted the research project Stable Russia – an evaluation of the security situation in Finland’s neighbourhood. The goal of the project was to paint an all-round picture of the factors affecting stability in Russia as well as possible destabilizing developments which could alter the security situation close to the Finnish borders. The project comprehensively tapped into Finnish Russia-expertise. This publication is based on the reports written for that project

Immunoglobulin production by cultured lymphocytes of patients with rheumatoid arthritis : association with disease severity

The synthesis of immunoglobulin (Ig) in cultures of mononuclear cells from the blood of patients with recent onset rheumatoid arthritis (RA) was studied. B lymphocytes were activated with mitogenic activators, pokeweed mitogen and Staphylococcus aureus Cowan I, and with Epstein-Barr virus (EBV). Ig production was assayed by counting the number of Ig-secreting cells and by determining the concentration of secreted Ig in the culture medium. The patients were followed by medical examinations, radiography, and clinical laboratory tests at six month intervals for two years. Mitogen-induced Ig synthesis by the cells of patients was significantly decreased compared to healthy subjects. The decreased responses were evident already at diagnosis before any disease-modifying anti-rheumatic medication was started. The mechanism of decreased responses were then studied by supplementing the cultures with modifying agents to examine the contribution of B cells, T cells and monocytes to the impaired Ig synthesis. Phytohaemagglutinin-induced interleukin-2 (IL-2) production was also studied. The low responses of rheumatoid lymphocytes to mitogens is, according to these experiments, due to poor helper function, possibly mediated by reduced production of IL-2. Further, the association of the in vitro responses with disease outcome was studied. Impaired mitogen-induced IgM production, as well as decreased PHA-induced IL-2 release, at the onset of disease, associated with joint destructions two years later. EBY -induced Ig response was associated with the disease: cultured mononuclear cells of patients with severe disease were not able to down-regulate excessive Ig synthesis in long term cultures. When used as a test high EBY-induced Ig synthesis predicted with a high probability the development of joint erosions and a poor outcome of disease. The in vitro assessment of immune functions may make it possible to develop tests which identify already in the early phase of disease the patients in risk to have destructive disease

Loss of density-dependence and incomplete control by dominant breeders in a territorial species with density outbreaks

Background: A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression. Results: We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density. Conclusions: At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.peerReviewe

Effects of UV Radiation and Diet on Polyunsaturated Fatty Acids in the Skin, Ocular Tissue and Dorsal Muscle of Atlantic Salmon (Salmo salar) Held in Outdoor Rearing Tanks

The effect of UV radiation (UVR) on juvenile Atlantic salmon (Salmo salar) was assessed by measuring the fatty acid (FA) profiles of muscle, dorsal and ventral skin, and ocular tissues following 4-month long exposures to four different UVR treatments in outdoor rearing tanks. Fish were fed two different diets (Anchovy- and Herring-oil based) that differed in polyunsaturated fatty acid (PUFA) concentrations. Anchovy-fed salmon had higher concentrations of ALA (alpha-linoleic acid; 18:3n-3), EPA (eicosapentaenoic acid; 20:5n-3) and DPA (docosapentaenoic acid, 22:5n-3) in their muscle tissues than fish fed the Herring feed. Fish subjected to enhanced UVB levels had higher concentrations of LIN (linolenic acid, 18:2n-6) and ALA, total omega-6 FA and SAFA (saturated fatty acids) in their tissues compared with fish in reduced UV treatments. Concentrations of ALA, LIN, GLA (gamma-linolenic acid; 18:3n-6), EPA, PUFA and total FA were higher in ventral skin of fish exposed to enhanced UVB compared with fish in reduced UV treatments. Salmon exposed to reduced UV weighed more per-unit-length than fish exposed to ambient sunlight. The FA profiles suggest that fish exposed to UV radiation were more quiescent than fish in the reduced UV treatments resulting in a buildup of catabolic substrates