In sexual organisms, low population density can result in mating failures and subsequently yields a low population growth rate and high chance of extinction. For species that are in tight interaction, as in host-parasitoid systems, population dynamics are primarily constrained by demographic interdependences, so that mating failures may have much more intricate consequences. Our main objective ...

Functional response describes the number of prey or hosts attacked by a predator or parasitoid as a function of prey or host density. Using three different experimental designs, we found a linear functional response by two insect parasitoids (the pteromalid Pachycrepoideus vindemiae and the diapriid Trichopria drosophilae) to their hosts (the drosophilids Drosophila suzukii and D. melanogaster)...

Host legumes can enrich their immediate soil environment with rhizobia through rhizosphere effects. The extent to which this enrichment occurs, the specificity of the process and its interaction with soil management factors remain poorly described. In a series of field trials, we measured changes in the size of indigenous populations of Bradyrhizobium in response to cropping of host and non-hos...

Disease is often expected to limit host populations, but diseases do not always dramatically reduce host numbers and often have no effect. The impact of a fungal pathogen (Entomophaga grylli pathotype 1) on grasshopper (Camnula pellucida) populations was studied in a field experiment. We tested whether the effects of disease on grasshopper survival were additive, with disease mortality summing ...

Symbiotic associations often enhance hosts' physiological capabilities, allowing them to expand into restricted terrains, thus leading to biological diversification. Stable maintenance of partners is essential for the overall biological system to succeed. The viviparous tsetse fly (Diptera: Glossinidae) offers an exceptional system to examine factors that influence the maintenance of multiple s...

Host-mediated responses and parasite density-dependent processes can have a major influence on the growth and fecundity of parasitic nematodes. However, host characteristics and parasite intensity consistently change during the course of an infection and these could affect worm length and number of eggs in a non-constant way. We used a free-living population of rabbits naturally infected with T...

The observed redshifts and magnitudes of the host galaxies of gamma-ray bursts (GRBs) are compared with the predictions of three basic GRB models, in which the comoving rate density of GRBs is (1) proportional to the cosmic star formation rate density, (2) proportional to the total integrated stellar density and (3) constant. All three models make the assumption that at every epoch the probabil...

When infectious disease transmission is density-dependent, the risk of infection will tend to increase with host population density. Since host defence mechanisms can be costly, individual hosts may benefit from increasing their investment in immunity in response to increasing population density. Such "density-dependent prophylaxis" (DDP) has now indeed been demonstrated experimentally in sever...

Host-parasite dynamics and strategies for managing infectious diseases of wildlife depend on the functional relationship between disease transmission rates and host density. However, the disease transmission function is rarely known for free-living wildlife, leading to uncertainty regarding the impacts of diseases on host populations and effective control actions. We evaluated the influence of ...