The Relative Roles of Dispersal and Establishment for Shaping Whole-Lake Aquatic Macrophyte Richness, Diversity, and Community Structure in Hemiboreal Lakes

Aquatic macrophyte diversity and structure play an important role in freshwater communities, yet little research on macrophytes has focused on native communities in the undisturbed hemiboreal lakes of North America. We used data collected from 15 inland lakes on Isle Royale National Park (Michigan, USA) to identify relationships among macrophyte metrics that describe dispersal and introduction potential (richness, diversity, community structure via growth form, and connectivity) and lake metrics that control establishment and growth potential. Results from partial least square regression analyses found that the most important and recurring predictors were those corresponding to establishment and growth. Alkalinity was the major contributor to the variation seen in richness, Shannon evenness, and Simpson inverse diversity metrics. Sediment phosphorus also contributed significantly to richness and diversity, but negatively. For growth form, half of the variation in submersed species related to alkalinity while almost half of variation in emergent species related to alkalinity and water color. Most of the variation in floating-leaved species was negatively related to alkalinity and water color. Our results suggest a high relative importance of establishment and growth metrics compared to introduction and dispersal metrics for understanding native macrophyte communities in North American hemiboreal lakes.