Variation in size and shape of American Pipit (Anthus rubescens) eggs was studied from 1987 to 1989 at two sites in the Beartooth Mountains, Park County, Wyoming. Differences in four egg traits were detected within clutches among females for all years and at both sites; there were differences between years and sites as well. Coefficients of variation for clutch means ranged from 1.52 (breadth) to 5.02 (volume). Mean repeatability estimates (± SD) of four independent samples were 0.75 ± 0.05, 0.64 ± 0.08, 0.70 ± 0.10, and 0.70 ± 0.08 for length, breadth, volume, and elongation, respectively, suggesting a significant heritable component in the phenotypic variation of egg size and shape. The difference between mean length and breadth repeatabilities was significant (P < 0.02). Repeatabilities of volume were the most variable of all traits and varied between years by as much as 22%, and between sites in 1989 by as much as 19%. Site differences are probably due to local environmental effects, and not a result of differences in the underlying genotypic variance. Repeatability estimates for American Pipit eggs were similar to those for a variety of bird species breeding in very different habitats. However, repeatability estimates can be calculated several ways and caution should be used when comparing estimates until it can be shown that these estimates are comparable for the same population.
Environmental effects on molecular and phenotypic variation in populations ofEruca sativaacross a steep climatic gradient
