Olivia deBourcier | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Olivia deBourcier. This seminar is open to the general public to attend.

MSc with Drs. Carol Frost and John Acorn.

Thesis Topic: Spatial Characteristics of Urban Wetlands Have an Unexpectedly Negligible Effect on Migratory Corixid and Aquatic Beetle Abundance, Species Richness, and Diversity 

Abstract: 

Urban growth often corresponds with a loss of wetlands, reducing the critical habitat for many species. Stormwater ponds, constructed to regain lost wetland function in urban centres, offer a novel type of habitat that supports a variety of organisms and have been shown to contain comparable invertebrate diversity to natural wetlands. Water boatmen (Hemiptera: Corixidae) and aquatic beetles (Coleoptera: Dytiscidae, Haliplidae, and Hydrophilidae) are common and functionally important invertebrates in urban ponds that supplement the diets of fish and other vertebrates, and predate on mosquito larvae. Both groups disperse primarily by flight. Water boatmen, in particular, undergo migration from rivers to ponds for the breeding season and return to rivers, such as the North Saskatchewan River, in the fall. The city of Edmonton, Alberta, Canada is divided by the North Saskatchewan River and contains over 350 stormwater management ponds of various sizes, spread across 627.2 km². This study examined how the spatial characteristics of stormwater ponds (area, connectivity, and distance to the river) affect the abundance, species richness, and diversity of corixids and aquatic beetles, with the goal of informing management practices to support invertebrate diversity. To test this, I sampled invertebrates from 36 of Edmonton’s stormwater ponds across two summers. Data on pond area, the amount of other wetland area around ponds (pond connectivity), and the distance of a pond to the North Saskatchewan River were acquired using GIS and data from the City of Edmonton. Each pond was sampled once per summer using dip netting and baited bottle trapping at three microhabitats at the edge of each study pond, and corixids and beetles were identified to the species level. In total, I collected and identified 3,912 corixids and 5,797 beetles. I used general(ized) linear models to test the additive and interactive effects of pond area, connectivity, Julian week (and distance to the river for corixids), plus all interactions on abundance, species richness, and Shannon diversity for each insect group. I found that, contrary to my hypotheses based on island biogeography theory and metacommunity ecology theory, corixid and aquatic beetle populations were weakly and inconsistently affected by the spatial arrangement and size of their habitat. Other studies have found similar decoupling between spatial variables and community composition among corixids and beetles, in addition to other macroinvertebrates, and have suggested that strong dispersal capacities among corixids and beetles provide them with the ability to choose habitat based primarily on habitat preferences