Sex–linked inheritance of host–plant specialization in a polyphagous butterfly

I investigated the genetic background of intraspecific variation in oviposition specificity in the generalist butterfly Polygonia c–album. Using reciprocal crosses between two populations that differ in their degree of specialization, I show that specificity is strongly sex–linked. This indicates that genes determining this difference are located primarily on the paternally inherited X–chromosome. The results suggest that intraspecific differences in specificity are caused by the same genetic mechanisms that have been shown to determine interspecific differences in host–plant ranking in other butterflies. Accordingly, the common assumption that specialization and ranking are determined by fundamentally different mechanisms was not supported.