Alien species numerically dominate natural enemy communities in urban habitats: A preliminary study

Abstract

Urbanization generally leads to reduced biodiversity of insects, mainly native species. Knowing the structure of natural enemy communities is important because of the significant role they play as biological control agents of herbivores. Here, we evaluated the influence of urbanization on the complex of natural enemies of the aphid Aphis gossypii (Hemiptera Aphididae), which feeds on the flowers of jacaranda (Jacaranda mimosifolia, Bignoniaceae). Seven sites with different urbanization levels were selected in the city of Córdoba (central Argentina) and three jacaranda trees with aphids were sampled in each site. Diversity, a and relative contribution of native and alien species were estimated. In general, the results indicate that urbanization did not have a significant effect on the community of natural enemies, with species richness showing a marginally significant increase with increasing urbanization levels. Although a similar richness of native and alien species was recorded across sites, 80% of natural enemy abundance belonged to alien species. Aphid populations were found to increase with increasing level of urbanization, but this variable did not have an influence on natural enemies. The dominance of alien and/or generalist species resistant to disturbances might account for the lack of relationship between urbanization and structure of natural enemy communities.