Backyard Biodiversity: An Analysis of Butterfly Richness and Abundance Within Suburban Habitat Types in Southeast Michigan

Abstract

Urbanization, urban sprawl, and the resulting rural-urban gradient have had major impacts on biodiversity, but few studies have investigated their effects on butterfly species in suburban habitats. The goal of this thesis is to investigate the variables characterizing different types of habitats within a suburban landscape and their resulting impacts on butterfly species richness and abundance, using butterfly sightings as a metric. It was predicted that the variables and habitats associated with higher levels of urbanization would have lower species richness and individual abundance. Observations were conducted via a point-count method; generalized linear models were constructed to predict butterfly species richness and individual abundance as a result of different landscape variables and habitat types, and a non-metric multidimensional scaling model was used to analyze the similarities and differences between butterfly communities at each habitat type. Only two variables — the proportion of flowering plant species and distance to the nearest building — had a significant effect on butterfly species richness and abundance. The highest species richness per survey point occurred in the garden habitat while the highest individual abundance per survey point occurred in the meadow habitat; however, butterfly communities were generally very similar across all habitat types. This thesis adds to the limited knowledge of butterfly communities in suburbs in general and in southeast Michigan, an area that has historically been understudied. Knowing what determines butterfly diversity and abundance in suburban areas may provide better guidance on how to maintain a rich community of butterflies and aid future conservation efforts in suburban cities.