The effects of host and habitat preferences in mate location of Monochamus maculosus, Monochamus notatus, and Monochamus scutellatus (Coleoptera: Cerambycidae)

Abstract

Several Monochamus species (Coleoptera: Cerambycidae) use monochamol as an aggregation-sex pheromone, raising questions about how they maintain reproductive isolation. Herbivorous insects use host plant semiochemicals as cues for mate location and, with or without habitat cues, these could confer reproductive isolation among sympatric Monochamus spp. To test this hypothesis, host and habitat preferences in mate location were examined for sympatric populations of Monochamus maculosus, Monochamus notatus, and Monochamus scutellatus in the Algoma District, Ontario, Canada. Field experiments were performed to investigate whether differences in host preference, vertical distribution across the forest canopy, spatial distribution within down and standing dead trees, or any combination of these factors could minimise cross-attraction to monochamol. Results showed that more M. maculosus were attracted to monochamol combined with jack pine foliage than with balsam fir or white spruce, whereas no differences in host attractivity were observed for the other species. Vertical abundance of M. maculosus and M. scutellatus was similar across forests. Spatial distribution provided limited evidence for species segregation within hosts. No evidence was found that host or habitat preferences contribute to reproductive isolation in M. maculosus, M. notatus, or M. scutellatus, suggesting that vertical distribution could be driven by resource availability.