Path analysis of natural selection via survival and fecundity across contrasting environments in Avena barbata.

We employed path analysis to analyse natural selection through two major fitness components in each of three contrasting environments. Using a randomized block design, 188 Recombinant Inbred Lines (RILs) derived from a cross between contrasting ecotypes of Avena barbata were planted in common gardens in the greenhouse, and in two field sites typical of each ecotype's native habitat. Individuals were monitored for germination phenology, early growth, survival, final size, flowering phenology, reproductive allocation, fecundity and lifetime reproductive success. The variance/covariance matrix of the RIL (genotype) means was fit to a path model in which total fitness was made up of survival and fecundity (of survivors) components. In the greenhouse, all fitness variation was determined by fecundity variation (with no mortality), which was itself primarily determined by reproductive allocation mediated by date of first flowering. By contrast, in the field, early growth was the major determinant of survival, and final size was the major determinant of fecundity. Both components of fitness affected lifetime reproductive success equally in the field. Thus the major difference between greenhouse and field seems to be a shift from selection on allocation patterns in adults, to selection on resource acquisition, especially at earlier life stages. The pattern of selection was similar in the two field sites, despite the contrasting environments.

Statistical method for quantifying mobile phase selectivity in one- and two-dimensional overpressured layer chromatography.

A method for selecting mobile phases for either one-dimensional (1-D) or two-dimensional (2-D) planar chromatography is described and is applied to the separation of steroids by overpressured layer chromatography [Formula: see text] a form of forced-flow thin-layer chromatography [Formula: see text] using both normal- and reversed-phase chromatography. Two metrics are used for evaluating the separation quality of simulated chromatograms for each of 100 (or more) subsets of a set of 30 steroids in each of 15 1-D, and 105 2-D systems. The subsets vary in size between five and 25 steroids. Butyl acetate/toluene on silica gel and aqueous 2,2,2-trifluoroethanol are, on average, the highest and second highest ranked 1-D systems, respectively, for separating all subset sizes. These two systems are the constituent members of the system that is, on average, the highest ranked 2-D system for all subset sizes. The probability of the above systems being highest ranked decreases with decreasing subset size. There is only a 17% probability of butyl acetate/toluene on silica being the best system for separating a subset of five steroids, while there is a 3% probability of this being the worst system for this subset size. The spot capacity of each system can be estimated by considering 100 subsets of each size and noting the largest subset size that yields an acceptable value of one of the metrics used for measuring separation quality. The mobile phase selectivity may be quantified using the actual values of either of the two separation metrics, or by a nonparametric approach. The latter is used in such a way that a difference of unity in the ranking (for a given subset size) of two systems corresponds to a 95% probability that the higher ranked system will yield the better separation.

Susceptibility of male white-tailed deer (Odocoileus virginianus) to Brucella ovis infection.

Infection with Brucella ovis was established by conjunctival instillation in 8 male white-tailed deer (Odocoileus virginianus). Infection was transient in young bucks, but persisted in bucks that were mature when inoculated. The deer were euthanatized and necropsied at various intervals after inoculation. Brucella ovis was recovered from a mature buck at necropsy on postinoculation day 429. Four deer had gross lesions and histopathologic changes of the epididymides. A mature noninfected buck confined for 7 months with an infected buck acquired infection and developed epididymal lesions.