Genetic variation among populations of Pissodes strobi (white pine weevil) reared from Picea and pinus hosts as inferred from RAPD markers

• Main Author: Lewis, Kornelia G.
• Format: Others
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/4008

The white pine weevil, Pissodes strobi, is an insidious pest of spruce regeneration in British Columbia and has forced forest managers to virtually eliminate the planting of Sitka spruce in coastal B.C. This leader weevil is capable of feeding on a wide variety of conifers and in B.C., P. strobVs preferred hosts are species of spruce. This attack pattern is counter to that observed in eastern Canada where species of pine are the major hosts attacked. The RAPD marker technique was used to examine genetic variation within and among populations of P. strobi across it's range in B.C. This was done to assess population structure and to determine if P. strobi populations are distinct relative to host tree species. Weevils were collected from a total of 12 populations: five Sitka spruce (three of which were from Vancouver Island and two from the mainland), three white spruce and two Engelmann spruce from the B.C. interior and two Jack pine (obtained from Ontario) populations. The bulked DNA technique was initially explored in an attempt to identify genetic markers specific to the Y chromosome (these in essence being haploid markers). Six putative male specific markers were tentatively identified. However, dot-blots failed to confirm the genomic specificity of these markers so the genetic variation was assessed using RAPD markers generated from diploid DNA. From each population DNA was extracted from 30 individuals (15 males; 15 females). Ten different primers were used with each of the 360 DNA extracts and 69 polymorphic RAPD markers were made available for analysis. Since there was no general consensus as to how to analyze RAPD data, markers were used to estimate allele frequencies as well as being treated as simple binary type data (presence or absence of band). Population genetic analyses, based on the allele frequency data, included examining the percentage of polymorphic loci, mean expected heterozygosity, Wright's F-statistics, and cluster analyses (three different methods tested with three different genetic distances/similarities). Multivariate analyses was performed with the binary coded data and included principal component analysis as well as parametric and nonparametric discriminant procedures. Both multivariate and population genetic analyses indicated the following: 1) populations of P.strobi from Sitka spruce on Vancouver Island are distinct from populations obtained from mainland B.C. Sitka spruce; 2) populations of P. strobi collected from Engelmann and white spruce form a distinct complex thus, for management purposes investigators should recognize three groups of P. strobi in B.C. and; 3) P. strobi reared from the eastern host, Jack pine, are most similar to the Engelmann/white spruce complex. === Forestry, Faculty of === Graduate