| Summary: | Arbutus (Arbutus menziesii Pursh) is the only broadleaved evergreen tree native to
Canada. It is a member of four natural plant communities in British Columbia (BC) considered
to be at risk as identified by the BC Conservation Data Centre, the main contributing factors
being urban encroachment, fire suppression, grazing and exotic invasive species. Very few
studies have been conducted on this species, and no data is available on pollination biology or
population genetics. Amplified fragment length polymorphisms (AFLPs) were used to conduct
the first genetic examination of A. menziesii in BC. The study included 10 populations spread
throughout the geographic range of arbutus in BC as well as one population from Washington
State. Genetic diversity estimates were low (mean H within populations = 0.094) relative to
long-lived perennials on average (0.25); there were no significant differences among
populations. Significant partitioning of genetic variation among populations was detected (FST =
0.15, ΦST = 0.16). This estimate was comparable to the average in long-lived perennials and
frugivores-dispersed species (FST = 0.19 and 0.16, respectively). Jackknifed estimates of FST , a
dendrogram of Reynolds' coancestry coefficient for all populations and a principal components
analysis all suggested that the Gold River, BC population seemed to differ more from other
populations, although this trend was not statistically significant. Isolation by distance was
significant based on kinship coefficients (p < 0.01): half-sibs were approximately three metres
apart. Mating system analysis of the Amelia Island, BC population revealed a high outcrossing
rate (0.97), although 10-20% of mating events were attributed to biparental inbreeding. Pollen
flow in this population was also investigated using a paternity analysis. Due to the low genetic
variability detected in this species as well as the significant biparental inbreeding, the ability to
confidently assign paternity was limited. Comparison of paternity assignment at LOD score
threshold values of 4 and 5 revealed the characteristic leptokurtic distribution of pollen in many
other plant species. The information generated from this investigation is discussed with respect
to conservation strategies, and future directions in the study of the genetics of arbutus are
suggested.
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