Components of reproductive isolation between North American pheromone strains of the European corn borer.
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 resulted in nearly complete isolation (>99%), but geographic variation in seasonal isolation allowed as much as approximately 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 (Dopman et al. 2005), 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.
Dopman
Erik B
EB
Department of Biology, Tufts University, 163 Packard Avenue, Medford, Massachusetts 02155, USA. erik.dopman@tufts.edu
Robbins
Paul S
PS
Seaman
Abby
A
D000818:Animals; D002940:Circadian Rhythm; D019143:Evolution, Molecular; D005260:Female; D051456:Gene Flow; D049810:Genetic Speciation; D005854:Germ Cells / Q000502:physiology; D007246:Infertility; D008297:Male; D009036:Moths / Q000502:physiology*; D009656:North America; D010675:Pheromones / Q000502:physiology*; D012098:Reproduction / Q000235:genetics; D012621:Seasons; D012726:Sexual Behavior, Animal
D010675:Pheromones