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J Bergelson

Publications and source records attributed to J Bergelson.

21 records · Page 2Linked to original sources
PubMed1990

Statistical genetics of an annual plant, Impatiens capensis. I. Genetic basis of quantitative variation.

Analysis of quantitative genetics in natural populations has been hindered by computational and methodological problems in statistical analysis. We developed and validated a jackknife procedure to test for existence of broad sense heritabilities and dominance or maternal effects influencing quantitative characters in Impatiens capensis. Early life cycle characters showed evidence of dominance and/or maternal effects, while later characters exhibited predominantly environmental variation. Monte Carlo simulations demonstrate that these jackknife tests of variance components are extremely robust to heterogeneous error variances. Statistical methods from human genetics provide evidence for either a major locus influencing germination date, or genes that affect phenotypic variability per se. We urge explicit consideration of statistical behavior of estimation and testing procedures for proper biological interpretation of statistical results.

Genetic Variation↗
PubMed1990

Statistical genetics of an annual plant, Impatiens capensis. II. Natural selection.

Measurement of natural selection on correlated characters provides valuable information on fitness surfaces, patterns of directional, stabilizing, or disruptive selection, mechanisms of fitness variation operating in nature, and possible spatial variation in selective pressures. We examined effects of seed weight, germination date, plant size, early growth, and late growth on individual fitness. Path analysis showed that most characters had direct or indirect effects on individual fitness, indicating directional selection. For most early life-cycle characters, indirect effects via later characters exceed the direct causal effect on fitness. Selection gradients were uniform across the experimental site. There was no evidence for stabilizing or disruptive selection. We discuss several definitions of stabilizing and disruptive selection. Although early events in the life of an individual have important causal effects on subsequent characters and fitness, there is no detectable genetic variance for most of these characters, so little or no genetic response to natural selection is expected.

Least-Squares Analysis↗