Alexander Lapierre, MSc student in Wildlife Ecology & Management at the University of Alberta, Department of Renewable Resources
Supervised by Dr. Tyler Cobb and Dr. Carol Frost
The midcontinent Prairie Pothole Region of North America is characterized by millions of shallow depressions that form diverse wetlands. Ponded water bodies (ponds) in these wetlands that periodically dry up are highly variable and dynamic habitats that support productive aquatic invertebrate communities. However, many smaller, non-permanent ponds in the region have been consolidated into larger, permanent ponds.
Water boatmen (Hemiptera: Corixidae) are relatively diverse and common aquatic insects in the Prairie Pothole Region and are important in the diets of other wildlife. Their mass-migrations in the spring and fall between non-permanent ponds and large rivers are particularly important to energy flows and supporting other wildlife in the region. Pond consolidation increases pond permanence and reduces pond count and habitat diversity; therefore, we expected it to change prairie pothole water boatman species composition by reducing the relative abundance of migratory species, thereby reducing the migration potential of these communities.
I tested this by measuring pond consolidation in quarter sections managed by Ducks Unlimited Canada in Alberta's Central Parkland with a new area-based consolidation index. I selected 14 quarter sections that represented a gradient of pond consolidation and sampled these for water boatmen in late July and early August, 2024. Adult water boatmen were extracted from the samples, identified to species, and counted, then I used a Direct Gradient Analysis to test for associations between pond consolidation and species composition with water salinity included as an important covariate.
Two important migratory species, Callicorixa audeni and Sigara decoratella, were negatively associated with pond consolidation. These results suggest that consolidating numerous, non-permanent ponds into fewer, permanent ponds changes water boatman communities by reducing the relative abundance of some key migratory species, thereby reducing the potential of these communities to contribute to seasonal mass-migrations in the northwest Prairie Pothole Region.
We show a previously unknown consequence of pond consolidation on an aquatic invertebrate community in the Prairie Pothole Region. To mitigate the loss of smaller, non-permanent ponds and support the migration-related ecosystem services of water boatman communities in this region, I recommend targetting areas with unconsolidated pond groups for conservation and further incentivizing land owners to avoid removing groups of small, non-permanent ponds.
Myself and Andrés Martinez Mayorga collecting water boatmen at a prairie pothole pond in August, 2024. Photo by Solomiya Kucharyshyn.