QUANTITATIVE GENETICS OF THE WING COLOR PATTERN IN THE BUCKEYE BUTTERFLY (PRECIS-COENIA AND PRECIS-EVARETE) - EVIDENCE AGAINST THE CONSTANCY OF G

Models for the evolution of continuously varying traits use heritabili ties, genetic correlations, and the G-matrix to quantify the genetic v ariation upon which selection acts. Given estimates of these parameter s, it is possible to predict the long-term effects of selection, infer past selective forces responsible for observed differences between po pulations or species, and distinguish the effects of drift from select ion. Application of these methods, however, requires the unproven assu mption that the G-matrix remains constant from one generation to the n ext. This study examines the assumption of constancy for the wing patt ern characteristics of two sibling species of butterflies, Precis coen ia and P. evarete (Lepidoptera: Nymphalidae). Quantitative genetic par ameters were estimated from parent offspring regression. Two approache s were taken to test the null hypothesis of equality between species. First, pairwise tests between corresponding elements of G and between heritabilities and genetic correlations for the two species were const ructed. Second, a modification of Bartlett's modified likelihood-ratio test was used to test for equality between the G-matrices. The matrix test failed to detect any between species differences. In contrast, p airwise comparision revealed significant differences. Thus, it appears that constancy cannot be assumed at the species level in quantitative genetic studies. In particular, the assumption of constancy was viola ted for the trait with the greatest difference in mean phenotype.