Randomly amplified polymorphic DNA reveals fine-scale genetic structure inPissodes strobi(Coleoptera: Curculionidae)

Abstract

To confirm patterns of diversity and differentiation found with isozymes and mitochondrial DNA, we surveyed 10 populations of the white pine weevil,Pissodes strobi(Peck), for randomly amplified polymorphic DNA (RAPD) markers. Four weevil populations were sampled from Sitka spruce,Picea sitchensis(Bong.) Carr (Pinaceae), five from the "interior" spruce of British Columbia [admixtures of white spruce,Picea glauca(Moench) Voss, and Engelmann spruce,Picea engelmanni(Parry)], and one from Jack pine,Pinus banksianaLamb. (Pinaceae), in Ontario. In each population, 30–60 weevils were assayed with 10 RAPD primers, yielding 74 RAPD markers. Genetic analyses showed that populations from interior spruce and Jack pine formed a distinct complex; as well, Vancouver Island populations formed a distinct group within the Sitka populations. Levels of diversity, both in terms of polymorphic loci and expected heterozygosity, declined from east to west, supporting the contention thatP.strobioriginated in eastern North America and migrated west, and suggesting that biocontrol methods may be more effective on populations from Sitka spruce, owing to their reduced diversity. These results parallel an earlier isozyme study but, in contrast, the diversity differences and population relationships are demonstrated to be statistically significant, owing to both the much larger number of loci sampled and the attachment of statistical confidence intervals to estimates of diversity and differentiation.