Experimental analysis of the mating system of the white pine weevil,Pissodes strobi(Peck) (Coleoptera: Curculionidae)

Abstract

The white pine weevil, Pissodes strobi, severely restricts the growth and range of Sitka spruce (Picea sitchensis) in British Columbia. Knowledge of the patterns of male and female mating success is important for designing biocontrol programs and for understanding the reproductive potential of this weevil. To examine patterns of male and female reproductive success, we performed experiments in which the numbers of competing mates were varied, and used microsatellite markers to assay for mating success. Matings were conducted under four regimes: two males competing for a female, four males competing for a female, two females competing for a male, and four females competing for a male. We assayed 1869 progeny among several replicates for four marker loci. We found considerable multiple paternity, and the variance of reproductive success was higher in males than in females. The normalized variance of male success was higher among four competing males than between two competing males, which is consistent with last-male sperm precedence, while the normalized variance of female success was independent of female number for a constant male number, indicating that sperm quantity was not a limiting factor for reproduction at these mate densities.