Pond consolidation in the northwest Prairie Pothole Region changes water boatman (Hemiptera: Corixidae) species composition and reduces potential contribution to seasonal mass-migrations.Lapierre et al. (under review 2025).

Ongoing consolidation of numerous, smaller, non-permanent ponds into fewer, larger, permanent ponds in the Prairie Pothole Region of North America raises concern for species and ecosystem processes that may depend on clusters of small, non-permanent ponds. Water boatmen (Hemiptera: Corixidae) are common aquatic insects in this region and their mass-migrations in the fall from non-permanent ponds to rivers are particularly important to energy flows and supporting other wildlife in the region. We hypothesized that pond consolidation would reduce the abundance of migratory water boatmen and species richness, and change species composition by selecting against migratory species, with implications water boatman export from ponds to rivers.We tested this by measuring pond consolidation in quarter sections in Alberta, Canada with a new area-based consolidation index. We selected 14 quarter sections that represented a gradient of pond consolidation and sampled from six locations in each quarter section in the late summer and late fall of 2024, before and after the fall mass-migration. Adult water boatmen were extracted from the samples, identified to species, enumerated, then sample counts were pooled by quarter section. We found a 54% reduction in migratory water boatman abundance as pond consolidation increased, and that two species that dominate seasonal mass-migrations, Callicorixa audeni and Sigara decoratella, were negatively associated with pond consolidation. We found a non-significant decrease in species richness due to pond consolidation. We estimated that increasing pond consolidation from our minimum observed consolidation index score to our maximum results in a loss of 2.6 kg of adult migratory water boatman biomass per quarter section. We show a previously unknown consequence of pond consolidation on water boatmen in the Prairie Pothole Region, with implications for the important ecosystem services that they provide. To mitigate the loss of smaller, non-permanent ponds and support the migration-related ecosystem services of water boatman communities in this region, we recommend targeting areas with unconsolidated pond groups for conservation.