Differences in Diel Timing of Flight May Reduce Hybridization Between Native and Introduced Geometrid Moth Congeners

Abstract

Hybridization between exotic and native species can lead to negative ecological and economic consequences. The invasive winter moth (WM), Operophtera brumata, uses the same sex-attractant pheromone and mates and produces fertile offspring with a native congener the Bruce spanworm (BSW), O. bruceata, and a stable hybrid zone has formed where their ranges overlap in the northeastern United States. However, the fact that the two species have not merged, despite seasonal overlap of flight, suggests that one or more pre- or post-mating barriers to hybridization might therefore exist. Here, we evaluate the hypothesis that interspecies differences in diel timing of flight might provide pre-mating isolation and explore whether these two species change their diel timing of flight differently in response to changes in temperature. Our results indicate that the flight timing of WM and BSW broadly overlap during the nighttime hours, although WM males fly almost exclusively at dawn, dusk, and night whereas BSW males fly during both daytime and nighttime hours. Flight activity also differed between the two species in response to nighttime temperatures < 0 °C, wherein WM flight largely stopped while BSW flight continued and the proportion of males flying during the daytime increased. This partial partitioning may help explain why the native BSW has not been completely outcompeted by the invasive WM.

Citation

Chandler, Jennifer L.; Elkinton, Joseph S.; Boettner, George H.; Andersen, Jeremy C. 2025. Differences in Diel Timing of Flight May Reduce Hybridization Between Native and Introduced Geometrid Moth Congeners. Journal of Insect Behavior. 38: 6. 10 p. https://doi.org/10.1007/s10905-025-09870-5.