INHERITANCE OF PHEROMONE PRODUCTION IN THE SULFUR BUTTERFLIES COLIAS-EURYTHEME AND COLIAS-PHILODICE

The inheritance of male pheromone production in the sulfur butterflies C. eurytheme and C. philodice was determined by gas chromatographic analyses of wing extracts from various genotypes derived from interspecific crosses. A wing UV-reflectance pattern (found only in C. eurytheme males) which is controlled by an X-linked gene served as a marker for determining the relative influence of this chromosome vs. the autosomes on pheromone production. Production of the most important C. philodice wing compounds, 3 different n-hexyl esters, is apparently controlled by 1 or more autosomal genes that are at least codominant. The X chromosome carries most of the genes or the gene controlling production of the most important C. eurytheme compound, 13-methyl heptacosane. Expression of this compound in hybrids displays a codominant pattern. Because the wing UV-reflectance pattern of male C. eurytheme is an important courtship signal, it appears that all of the genes controlling the male courtship signals of this species are inherited as a coadapted gene complex on the X chromosome. The evolution of X chromosomal control of both the visual (wing UV-reflectance pattern) and olfactory (13-methyl heptacosane) components of the courtship communication system of C. eurytheme is discussed and compared to the mode of inheritance of other communication systems.