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Thesis Abstract – Woods (2010)


Effects of Habitat Fragmentation on Beetle Biodiversity in Southern California

Author and college:

Sarah Woods, Pomona College


May, 2010


Bachelor of Arts in Biology


Frances Hanzawa, Pomona College


Population growth has resulted in the rapid expansion of suburban areas across the United States, destroying large areas of natural habitat, particularly the endangered coastal sage scrub plant community in Southern California. Habitat destruction can partially or completely fragment areas of natural landscape, resulting in smaller patches or isolated islands of habitat. As a result, ecological effects such as decreased diversity, abundance, and genetic variability can result in plant and animal organisms within the habitat. Ecological changes of interior biota due to fragmentation are known as edge effects. In this study, I assessed (1) whether species diversity and abundance differed between fragmented areas of varying size (2) and whether species diversity and abundance differed between the interior and the edge in fragmented areas of varying size and isolation. The species richness and abundance of ground-dwelling beetles (Coleopterans) were assessed at two fragmented sites: the smaller, Robert J. Bernard Biological Field Station (BFS) and the larger, North Etiwanda Preserve (NEP). The results show how the size of a habitat influences biodiversity and how edge conditions can influence the interior of the habitat. I found greater beetle diversity and abundance in the larger habitat compared to the smaller habitat. Additionally, edge conditions resulted in greater beetle abundance in the interior of NEP. However, the smaller habitat, BFS, demonstrated greater beetle abundance in the edge, possibly due to invasive species. There was no relationship between species richness and distance from edge at both sites. Results also suggest an edge effect that penetrates ~200 meters into NEP, which leads to the conclusion that BFS is essentially an edge because of its small size and isolation. These results demonstrate the effects of human-induced fragmentation and advocate the need of maintaining current habitats and fragments at the largest possible size to minimize effects of fragmentation.

For more information:

Contact Frances Hanzawa – frances.hanzawa@pomona.edu

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