COMPONENTS OF REPRODUCTIVE ISOLATION BETWEEN NORTH AMERICAN PHEROMONE STRAINS OF THE EUROPEAN CORN BORER

摘要

Of 12 potential reproductive isolating barriers between closely related Z and E pheromone strains of the European corn borer moth (Ostrinia nubilalis), seven significantly reduced gene flow but none were complete, suggesting that speciation in this lineage is a gradual process in which multiple barriers of intermediate strength accumulate. Estimation of the cumulative effect of all barriers was nearly complete isolation (> 99%), but geographic variation in seasonal isolation allowed as much as ~10% gene flow. With the strongest barriers arising from mate-selection behavior or ecologically relevant traits, sexual and natural selection are the most likely evolutionary processes driving population divergence. A recent multilocus genealogical study corroborates the roles of selection and gene flow (), because introgression is supported at all loci besides Tpi, a sex-linked gene. Tpi reveals strains as exclusive groups, possesses signatures of selection, and is tightly linked to a QTL that contributes to seasonal isolation. With more than 98% of total cumulative isolation consisting of prezygotic barriers, Z and E strains of ECB join a growing list of taxa in which species boundaries are primarily maintained by the prevention of hybridization, possibly because premating barriers evolve during early stages of population divergence.