Assortative mating in sympatric host races of the European corn borer.

Although a growing body of work supports the plausibility of sympatric speciation in animals, the practical difficulties of directly quantifying reproductive isolation between diverging taxa remain an obstacle to analyzing this process. We used a combination of genetic and biogeochemical markers to produce a direct field estimate of assortative mating in phytophagous insect populations. We show that individuals of the same insect species, the European corn borer Ostrinia nubilalis, that develop on different host plants can display almost absolute reproductive isolation-the proportion of assortative mating was >95%-even in the absence of temporal or spatial isolation.

Managing the evolution of Bacillus thuringiensis resistance in natural populations of the European corn borer, Ostrinia nubilalis: host plant, host race and pherotype of adult males at aggregation sites.

The European corn borer (ECB) consists of at least two, genetically differentiated host races: one feeding on maize, the other feeding on mugwort and hop. It is unclear to what extent individuals feeding on these, or other host plants, contribute to natural ECB populations. The mechanisms underlying the genetic differentiation between both races are not well understood; they may include sexual attraction via different pheromone blends (E or Z) and differences in the location of mating sites.

Genetic isolation between two sympatric host-plant races of the European corn borer, Ostrinia nubilalis Hübner. I. Sex pheromone, moth emergence timing, and parasitism.

Adaptation to different environments may be a powerful source of genetic differentiation between populations. The biological traits selected in each environment can pleiotropically induce assortative mating between individuals of these genetically differentiated populations. This situation may facilitate sympatric speciation.