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UBC Theses and Dissertations

Species invasion in the marine fouling communities of British Columbia : factors that influence invasion dynamics and how they may affect Botrylloides violaceus Nelson, Jocelyn Christine


Species invasion has been recognized as a major threat to biodiversity. Knowledge of the factors that limit the establishment and spread of non-indigenous species (NIS), such as biotic resistance and unfavourable environmental conditions, are important to their effective management. To test the biotic resistance and environmental favourability hypotheses in the fouling communities of British Columbia (BC), 22 locations were compared using settlement tiles in a large-scale survey. Biotic resistance is believed to be stronger in more diverse communities, therefore NIS richness and abundance were compared to native species richness and environmental conditions to investigate their importance using generalized and linear mixed models. Invader taxonomic group may influence biotic resistance, and environmental tolerances vary by species, therefore factors that affected Botrylloides violaceus presence and abundance were investigated as a case study. The biotic resistance hypothesis was not supported for NIS richness or NIS abundance, but could not be fully discounted due to a trend toward a negative slope between native species richness and B. violaceus presence and abundance, and the absence of predator data. Environmental variables affected NIS: salinity had a positive influence on NIS richness, NIS abundance, and B. violaceus presence, and temperature had a positive effect on B. violaceus presence and abundance. Salinity had a positive impact on native species richness as well, supporting the environmental favourability hypothesis. This suggests that knowledge of relevant environmental conditions is more important for the management of invasive species than the species richness of vulnerable communities. Environmental conditions are not static, so species invasion must be considered in the context of climate change. To understand how climate change may influence species invasion, B. violaceus presence and abundance in BC were compared to a range of abiotic conditions. This comparison informed a GAMLSS model that used linear trends from historical shore station data to project potential abundance in BC forward 50 years. Overall, the abundance of B. violaceus in BC was projected to increase. A larger increase in B. violaceus abundance was forecast for locations where conditions increased into the range favourable for growth. If temperature and salinity become more favourable for B. violaceus, as projected, climate change could intensify the invasion.

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