Open Collections

Holt, Taylor

University of British Columbia

The alder bark beetle, Alniphagus aspericollis, is a hardwood-infesting bark beetle that attacks the bole of its host tree, red alder, Alnus rubra, and overwinters in branch-nodes as adults. This unique overwintering behaviour allows the investigation into drivers of lifecycle idiosyncrasies based on knowledge of other bark beetle systems. I chose to investigate the population structure and overwintering behaviours of the alder bark beetle, focusing on female-bias and branch- versus bole-overwintering sites, respectively. Beetles were collected from four sites in southwestern British Columbia. Sampling occurred in subcortical, bole-emerging, and branch-overwintering locations to collect beetles at various life stages and cohorts. For the population structure of the alder bark beetle, I hypothesized that a female-bias exists, driven by local mate competition and detected by sib-mating underneath the bark. This is further reinforced by size dimorphic, smaller males to be able to maximize the number of large, ovipositing females in the subcortical tissues. For alder bark beetle overwintering, I hypothesized that the observed branch-overwintering behaviour has evolved due to a heightened threat of mortality in the bole, facilitating rapid development to avoid entomopathogenic micro-organisms underneath the bark of natal host trees. Supporting my prediction for a female bias, the alder bark beetle population was found to have an average female proportion of 67%, with partial evidence towards sib-mating within the bole. Also, males were found to be smaller than females by 5%, a selection for smaller bodies to allow for more females to reside in the subcortical tissue. Branch-overwintering beetles were found to intercept the entomopathogen Beauveria more frequently in the bole than in the branches, with branch-overwintering beetles smaller in size than bole-overwintering beetles. Alder bark beetles in branch-overwintering sites were also found to be feeding throughout the winter, a strategy not commonly performed due to the mortality risks associated with increasing ice nucleation, leading to internal ice crystal formation. These results significantly improve the knowledge surrounding the alder bark beetle’s lifecycle, which is important as this beetle has the potential to cause widescale damage on riparian ecosystems through red alder mortality; a tree important for soil stability and nitrogen-fixation.

Text

2024-02-22

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87468

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/