Impact of urbanization on tri-trophic interactions in an endemic scrub community

Abstract

Human-mediated disturbances have altered every ecosystem on the planet and these changes may have important consequences for biodiversity and community structure. We tested how the degree of urbanization impacts a tri-trophic interaction among the Florida scrub endemic plant Palafoxia feayi, a gallmaking midge, and the associated parasitoid wasps. A combination of field surveys and laboratory rearings were used to determine whether habitat disturbance associated with housing development (e.g., land clearing, fire suppression) was correlated with changes in plant architecture, gallmaker abundance, or parasitoid diversity. We found significant differences in the number of side branches of plants at urban sites, and that the number of galls per plant increased with both the number of side branches and plant height. More parasitoids were found in galls collected from urban sites, but parasitoid diversity was unchanged by urbanization. We conclude that although urbanization influenced plant architecture, there was only a minor impact on gallmaker abundance and parasitoid diversity.