Butterfly community ecology: the influences of habitat type, weather patterns, and dominant species in a temperate ecosystem

Abstract We compared variation in butterfly communities across 3 years at six different habitats in a temperate ecosystem near B oulder, C olorado, USA . These habitats were classified by the local O pen S pace consortium as G rasslands, T allgrass, F oothills G rasslands, F oothills R iparian, P lains R iparian, and M ontane W oodland. Rainfall and temperature varied considerably during these years. We surveyed butterflies using the P ollard‐ Y ates method of invertebrate sampling and compared abundance, species richness, and diversity across habitats and years. Communities were most influenced by habitat, with all three quantitative measures varying significantly across habitats but only two measures showing variation across years. Among habitats, butterfly abundance was higher in P lains R iparian sites than in M ontane W oodland or G rassland sites, though diversity was lowest in P lains R iparian areas. Butterfly species richness was higher in F oothills R iparian sites than it was in all but one other habitat ( T allgrass). Among years, butterfly abundance and species richness were lower during the year of least rainfall and highest temperatures, suggesting a substantial impact of the hot, dry conditions. Across habitats and years, butterfly abundance was consistently high at P lains R iparian and F oothills R iparian sites, and richness and diversity were consistently high in F oothills R iparian areas. These two habitats may be highly suitable for butterflies in this ecosystem, regardless of weather conditions. Generally low abundance and species richness in M ontane W oodlands sites, particularly in 2002, suggested low suitability of the habitat to butterflies in this ecosystem, and this may be especially important during drought‐like conditions. Finally, to examine the effect that the presence of the very abundant non‐native species P ieris rapae L . ( L epidoptera: P ieridae) has on these communities, we re‐analyzed the data in the absence of this species. Excluding P . rapae dramatically reduced variation of both butterfly abundance and diversity across habitats, highlighting the importance of considering community membership in analyses like ours.