Understanding the relative contributions of landscape and local-scale processes shaping patterns of diversity is a central theme in community ecology. Although historically overlooked, cities exhibit strong but predictable landscape-scale gradients which overlay a mosaic of highly variables but repeated habitat types. As a result, urban environments provide a unique opportunity to explore the interactions between local and landscape-scale predictors of diversity in a system that is both rapidly expanding worldwide and highly relatable to a broad audience. We examined how fine-scale environmental variables (such as local temperature and relative humidity), habitat characteristics (including plant community composition) and broad-scale urbanization (including biophysical, human-built, and socio-economic variables) shape local insect communities in Los Angeles, CA. We used Malaise traps to collect insects in yards, parks, schools, and commercial properties stretching from the urban center to the periphery over the course of a year.
Results/Conclusions
We found that local environmental variables were the best predictors of insect species richness and abundance with the highest diversity occurring in drier and warmer sites across the city. Species composition generally followed broad-scale patterns of urbanization with more native insect communities occurring in less urbanized habitats and more cosmopolitan insects appearing in high frequency in highly urbanized areas. However, regardless of location within the urban landscape, the presence of native or drought tolerant plants in a habitat resulted in a > 35% increase in insect species richness and abundance and increased similarity in species composition across sites with a high incidence of native insects. Collectively, these results indicate that urban insect communities are a product of mechanisms functioning at both local and landscape scales. Nonetheless, changes to local environments can have positive effects on local diversity and promote native species, specifically if those changes aim at emulating the natural environments nearest the city.