Differing insect communities and reduced decomposition rates suggest compromised ecosystem functioning in urban preserves of southern California

Abstract

Conservation typically has dual objectives of preserving both biodiversity and ecosystem functioning; however, management of ecosystems is challenging. To address the conservation of ecosystem functions, we 1) described the insect community associated with the decomposition of small mammal carcasses, 2) assessed correlations between insects (abundance and community composition) and landscape cover types, and 3) quantified decomposition rates of a small mammal carcass in Mediterranean shrublands and grasslands of San Diego County, CA USA. Beetle families (Silphidae, Staphylinidae, Histeridae) and a fly family (Phoridae) exhibited a negative relationship with urban land cover and a positive relationship with sage scrub within 5 km of trapping locations. Decomposition rates of a small mammal carcass also exhibited a negative correlation with the proportion of urban landscape and positive correlation with sage scrub cover. While it is expected that differing land cover composition will result in different insect communities, we demonstrated how these different communities are directly tied to ecosystem function. Insects should be a greater focus of conservation efforts due to their high level of biodiversity, integral role in many ecosystem functions, and the recent documentation of global insect declines. Studies like ours provide a way for conservation efforts to shift focus from managing individual species to preserving ecosystem functions so that management can meet their stated goals.

Keywords

• Sage scrub
• Chaparral
• Urbanization
• Insect conservation
• Biodiversity
• Ecosystem function