1. Global change models predict the greatest impact in climate to occur in the northern polar region. Change in temperature will alter individual metabolism and has the potential to change community structure to an unknown degree. 2. The temperature-dependent energy budget of Arctic Daphnia middendorffiana was investigated by measuring respiration rates, ingestion rates and assimilation rates. ...

A traditional view is that sexual reproduction increases the potential for phenotypic evolution by expanding the range of genetic variation upon which natural selection can act. However, when nonadditive genetic effects and genetic disequilibria underlie a genetic system, genetic slippage (a change in the mean genotypic value contrary to that promoted by selection) in response to sex may occur....

Four chemical races were detected in Pulicaria dysenterica, when sampled within Europe, on the basis of the surface flavonoids present. One race uniquely contained quercetagetin 3,7-dimethyl ether and another 6-hydroxykaempferol 3,4'-dimethyl ether. A third race was based on plants having 6-hydroxykaempferol 3,7-dimethyl ether together with quercetagetin 3,7,3'-trimethyl ether. The fourth race ...

Explaining the repeated evolution of similar sets of traits under similar environmental conditions is an important issue in evolutionary biology. The extreme alternative classes of explanations for correlated suites of traits are optimal adaptation and genetic constraint resulting from pleiotropy. Adaptive explanations presume that individual traits are free to evolve to their local optima and ...

Removal samples from an irrigated pasture were used as a calibration technique for the D-Vac. Plots 4 m2 were enclosed with a frame, and 1 initial and 3 removal samples were taken. Equations are given for computing the population and probability of collecting an insect. For leafhopper adults, leafhopper nymphs, Orius insidiosus (Say), and corn flea beetle, Chaetocnema pulicaria Melsheimer, cali...

The ability of age-0 year yellow perch Perca flavescans to detect prey using visual and mechanosensory input was examined during laboratory feeding trials at varying light intensities. Perch were highly effective predators and captured Daphnia pulicaria with 94% overall foraging success at light levels ranging from 0 to 3400 lx. Maximum average reaction distances (5 0 0 8 cm, mean S.E.) occurre...

The planting of transgenic crops expressing Bacillus thuringiensis endotoxins is widespread throughout the world; the prolific increase in their application exposes nontarget organisms to toxins designed to control pests. To date, studies have focused upon the effects of Bt endotoxins on specific herbivores and detritivores, without consideration of their persistence within arthropod food webs....