Integrating Taxonomic and Trait-Based Approaches to Evaluate Beta Diversity of Freshwater Invertebrates as Bioindicators of Environmental Change in Western Canada

Lakes and streams are among the ecosystems most impacted by recent global change. Aquatic invertebrate communities have long been used as indicators (i.e., bioindicators) of anthropogenic and natural environmental changes. Morphologically defined species have traditionally been used to assess aquatic invertebrates as bioindicators. Later (i.e., 1970s), a species trait-based approach has been recommended in which features of species that define their ecological roles are used to translate taxonomic changes into potential impacts on ecosystem function. Major knowledge gaps exist about how complementary versus redundant these two approaches are across different types of aquatic communities, ecosystems, and environmental changes. My thesis research combines biomonitoring approaches, determining taxonomic and functional turnover (i.e., beta diversity) of mountain zooplankton and stream macroinvertebrate communities to gain insights into ecological factors and potential consequences for ecosystem function. Multivariate data analyses ranging from indirect to direct gradient analyses quantify and illustrate temporal and spatial beta diversities related to environmental change. My analyses of zooplankton communities in naturally fishless alpine lakes stocked with sportfish show that a shift in trait selection from initial tolerance of predation (e.g., body size) to subsequent potential for recolonization (e.g., asexual reproduction) explains their contrasting responses to fish introductions and later removal over several decades. At a broader landscape scale, my analyses indicate that climatic and sportfish variables mainly explain the spatial beta-diversities of zooplankton communities across 85 mountain lakes. However, these drivers are not closely related to the temporal beta-diversities observed within the lakes over the past 60 years. In contrast, spatial beta-diversity of stream macroinvertebrate communities and their traits across tributaries spanning the North Saskatchewan River watershed within Alberta best indicated shifts in human land uses against the backdrop of a natural biogeographical gradient. In conclusion, the high degree of redundancy observed between the taxonomic and trait-based beta diversities of each of these communities allowed for confident interpretation of the results, providing ecological insights into how they were indicative of environmental changes along both spatial and temporal scales. Future research should use such comparative approaches to focus, where possible, on testing the validity of assumptions and models commonly used in bioindicator investigations.

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