QUANTITATIVE GENETICS OF BUTTERFLY WING COLOR PATTERNS

Developmental processes exert their influence on the evolution of comp lex morphologies through the genetic correlations they engender betwee n traits. Butterfly wing color patterns provide a model system to exam ine this connection between development and evolution. In butterflies, the nymphalid groundplan is a framework used to decompose complex win g patterns into their component pattern elements. The first goal of th is work has been to determine whether the components of the nymphalid groundplan are the products of independent developmental processes. To test this hypothesis, the genetic correlation matrices for two specie s of butterflies, Precis coenia and Precis evarete, were estimated for 27 wing pattern characters. The second purpose was to test the hypoth esis that the differentiation of serial homologs lowers their genetic correlations. The ''eyespots'' found serially repeated across the fore - and hindwing and on the dorsal and ventral wing surfaces provided an opportunity to test this hypothesis. The genetic correlation matrices of both species were very similar. The pattern of genetic correlation measured between the different types of pattern elements and between the homologous repeats of a pattern element supported the first hypoth esis of developmental independence among the elements of the groundpla n. The correlation pattern among the differentiated serial homologs wa s similarly found to support the second hypothesis: pairs of eyespots that had differentiated had lower genetic correlations than pairs that were similar in morphology. The implications of this study are twofol d: First, the apparent developmental independence among the distinct e lements of wing pattern has facilitated the vast diversification in mo rphology found in butterflies. Second, the lower genetic correlations between differentiated homologs demonstrates that developmental constr aints can in fact be broken. The extent to which genetic correlations readily change, however, remains unknown. (C) 1994 Wiley-Liss, Inc.