The effect of spontaneous mutations on competitive ability

Understanding the impact of spontaneous mutations on fitness has many theoretical and practical applications in biology. Although mutational effects on individual morphological or life‐history characters have been measured in several classic genetic model systems, there are few estimates of the rate of decline due to mutation for complex fitness traits. Here, we estimate the effects of mutation on competitive ability, an important complex fitness trait, in a model system for ecological and evolutionary genomics, Daphnia. Competition assays were performed to compare fitness between mutation‐accumulation (MA) lines and control lines from eight different genotypes from two populations of Daphnia pulicaria after 30 and 65 generations of mutation accumulation. Our results show a fitness decline among MA lines relative to controls as expected, but highlight the influence of genomic background on this effect. In addition, in some assays, MA lines outperform controls providing insight into the frequency of beneficial mutations.     

Apparatus for the automated measurement of the responses of humans to odorants

An automated system for the measurement of the psychophysicaland physiological responses of humans to odorant stimulationof the nose and eyes is described. All aspects of the generationand production of odor stimuli, the recording of physiologicaland psychophysical responses of the subjects and the storageof data are managed by an Apple He computer. Both the nasaland ocular olfactometers are based on electronic mass flow controllerswhich are used to control the ratios of volume flow rates ofclean and odorant-saturated air. The output of each olfactometeris measured by a photo-ionization detector. Odor stimuli aredelivered to custom-fitted face masks, that allow separate stimulationof the nose and eyes, through Teflon (rtm) flow valves. A videocamera records the responses of the eyes and a pneumotachograph,in combination with a pressure transducer, records changes inrespiratory behavior. An electronic mouse is used to enter thesubject's psychophysical responses directly into the computer.The advantages of this methodology and its current and potentialapplications are discussed.