Additive effects of predator diversity on pest control caused by few interactions among predator species

1. Studies of the impact of predator diversity on biological pest control have shown idiosyncratic results. This is often assumed to be as a result of differences among systems in the importance of predator–predator interactions such as facilitation and intraguild predation. The frequency of such interactions may be altered by prey availability and structural complexity. A direct assessment of interactions among predators is needed for a better understanding of the mechanisms affecting prey abundance by complex predator communities. 2. In a field cage experiment, the effect of increased predator diversity (single species vs. three‐species assemblage) and the presence of weeds (providing structural complexity) on the biological control of cereal aphids were tested and the mechanisms involved were investigated using molecular gut content analysis. 3. The impact of the three‐predator species assemblages of aphid populations was found to be similar to those of the single‐predator species treatments, and the presence or absence of weeds did not alter the patterns observed. This suggests that both predator facilitation and intraguild predation were absent or weak in this system, or that these interactions had counteracting effects on prey suppression. Molecular gut content analysis of predators provided little evidence for the latter hypothesis: predator facilitation was not detected and intraguild predation occurred at a low frequency. 4. The present study suggests additive effects of predators and, therefore, that predator diversity per se neither strengthens nor weakens the biological control of aphids in this system.     

A Model of Human Muscle Energy Expenditure

A model of muscle energy expenditure was developed for predicting thermal, as well as mechanical energy liberation during simulated muscle contractions. The model was designed to yield energy (heat and work) rate predictions appropriate for human skeletal muscle contracting at normal body temperature. The basic form of the present model is similar to many previous models of muscle energy expenditure, but parameter values were based almost entirely on mammalian muscle data, with preference given to human data where possible. Nonlinear phenomena associated with submaximal activation were also incorporated. The muscle energy model was evaluated at varying levels of complexity, ranging from simulated contractions of isolated muscle, to simulations of whole body locomotion. In all cases, acceptable agreement was found between simulated and experimental energy liberation. The present model should be useful in future studies of the energetics of human movement using forward dynamic computer simulation.     

A set of microsatellite markers for an endangered arboreal marsupial,Leadbeater's possum

Leadbeater's possum is a small, cryptic nongliding petaurid, which is threatened by habitat loss due to the collapse of large hollow‐bearing trees and ongoing timber production in Victoria's central highlands. The recent decline of this species and the difficulties faced by researchers collecting field data has prompted the development of a suite of polymorphic microsatellite markers for application to the continuing conservation of the Leadbeater's possum.     

Mutual Exclusion of ATP,ADP and g-Strophanthin Binding to NaK-ATPase

THE (Na⁺+K⁺)-activated ATPase found in cell membrane fragments is for many reasons thought to be part of the active sodium pump system of cells. One of the arguments is that cardiac glycosides specifically inhibit the ATPase as well as the sodium pump^1–3. It has been proposed that the inhibition is due to an interaction between the glycosides and some phosphorylated form of the ATPase system^4–6.     

Polymorphic microsatellite markers for the Douglas‐fir pathogen Phaeocryptopus gaeumannii,causal agent of Swiss Needle Cast disease

Ten polymorphic microsatellite markers were isolated from Phaeocryptopus gaeumannii, causal agent of the Douglas‐fir foliage disease Swiss Needle Cast. The primer sets were tested on 60 isolates that had, with more conservative markers, previously segregated into three reproductively isolated lineages comprising nine genotypes. The microsatellite data yielded 46 multilocus genotypes that segregated into three groups identical to the three lineages previously recovered. Microsatellite genotypic diversity ranged from 0.85 to 0.99 within lineages and was lowest where both pathogen and host are exotic.