Cuticular Hydrocarbon Recognition in the Mating Behavior of Two Pissodes Species

Two sibling weevil species, Pissodes strobi Peck and P. nemorensis Germar (Coleoptera: Curculionidae), can form reduced-fitness hybrids in the laboratory, but neither their premating isolation mechanisms nor mating behaviors are well-understood. Cuticular hydrocarbons (CHCs) have been reported as crucial chemical cues in mating recognition in many insects, including weevils, and, thus, may also mediate the mating behavior of P. strobi and P. nemorensis. We conducted a series of behavioral observations, bioassays, and chemical analyses to investigate the role of CHCs in their mating behavior. Copulation behavior of both species followed similar steps: approaching, mounting, tapping, aedeagus extrusion, and copulation. In P. strobi, hexane extraction significantly reduced the number of successful male copulations compared with freeze-killed females. Conversely, significantly fewer P. nemorensis males copulated with dead females compared with live females. No significant differences were detected among hexane-extracted, freeze-killed or recoated female carcasses to P. nemorensis. These findings suggested that female cuticular extracts contain important cues in mate recognition in P. strobi but not in P. nemorensis. We identified 21 CHCs from both species with variation in abundances between sexes and seasons. Discriminant analysis revealed incomplete overlap of CHC compositions in females of the two species in summer, when hybridization potentially occurs.

Genetically based resistance to the white pine weevil in jack pine and eastern white pine

White pine weevil (Pissodes strobi Peck) damage was evaluated in one white pine (Pinus strobus L.) and four jack pine(Pinus banksiana Lamb) half-sib family test sites to determine the role of tree genotype in resistance to the weevil. Halfsibfamily explained a significant proportion of the variation in weevil attack at all sites. Estimates of family (0.16-0.54)and individual (0.09-0.24) heritabilities of jack pine resistance to white pine weevil were moderate. Estimates of family(0.37) and individual (0.22) heritability of resistance of white pine to the weevil were also moderate when the percentageof test trees damaged by the weevil was relatively low, but were insignificant four years later when more than three-quartersof trees were damaged. Significant positive correlations between mean tree height and mean incidence of trees damagedby the weevil were observed for four of seven site-years but relationships were weak, suggesting that any cost, withrespect to height growth, to breeding weevil resistant trees may be small.Key words: Pinus, Pissodes strobi, trade-offs, tree improvement, tree resistance, white pine weevil.

Molecular characterization of the entomopathogenic fungi Lecanicillium spp. (Deuteromycota: Hyphomycetes) isolated from white pine weevil, Pissodes strobi (Coleoptera: Curculionidae), in British Columbia

The entomopathogenic fungal genus Lecanicillium Gams and Zare includes species that are highly pathogenic to many genera of insects. Three species, Lecanicillium longisporum (Petch) Zare and W. Gams, L. muscarium (Petch) Zare and W. Gams, and L. pissodis Kope and Leal, were found to be entomopathogens of adult white pine weevils, Pissodes strobi (Peck), in coastal British Columbia. Morphological characteristics were used to identify these species, but variation in conidial shape and size made it difficult to classify some of the isolates into the correct species of Lecanicillium. To confirm the identity of these Lecanicillium species, we used molecular tools such as polymerase chain reaction – restriction fragment length polymorphism and DNA sequencing.