| Summary: | 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
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