Figure 4.

Principal components analysis of epigaeic beetle assemblages in aspen-dominated mixedwood forests in north-central Alberta, 1992–93 ACarabidaeBStaphylinidae. Each symbol represents the catch from a single pitfall trap averaged over two years. Black symbols represent the Lower Foothills Natural Region; open symbols represent the Central Mixedwood Subregion, light grey symbols represent the Dry Mixedwood Subregion and the dark grey symbols represent the Lower Boreal Highlands Subregion of the Boreal Forest Natural Region. Ellipses represent the standard deviation around the centroid of points in each group and dashed polygons represent the final nodes of the multivariate regression tree (MRT) model. The inset shows the major MRT nodes grouping lines based on assemblage structure.