Habitat degradation and introduction of exotic plants favor persistence of invasive species and population growth of native polyphagous fruit fly pests in a Northwestern Argentinean mosaic

Abstract

Expansion of agricultural land is one of the most significant human alterations to the global environment because it entails not only native habitat loss but also introduction of exotic species. These alterations affect habitat structure and arthropod dynamics, such as those among host plants, tephritid fruit flies, and their natural enemies. We compared abundance and dynamics of pest and non-pest tephritids and their natural enemies over a mosaic of habitats differing in structure, diversity and disturbance history on the Sierra de San Javier in Tucuman, Argentina. Our prediction was that conserved habitats would be more resistant to the establishment and spread of invasive tephritid species due in part to a greater abundance of natural enemies, a greater diversity of native species in the same family and trophic level, and a greater wealth of biotic interactions. We further predicted that native species with broad host ranges should be more sensitive to habitat loss yet more competitive in less disturbed habitats than generalist native and exotic species. We found that environmental degradation, and introduction and spread of exotic host plants strongly affected distribution patterns, abundance, and phenology of native and exotic tephritids. Monophagous tephritid species and several specialized parasitoids were more sensitive to habitat loss than polyphagous species and parasitoids exhibiting a wide host range. In contrast, native monophagous species and native parasitoids appeared to exclude the invasive Mediterranean fruit fly from conserved patches of native vegetation. Nevertheless, the Mediterranean fruit fly persisted in uncontested exotic host plants and thrived in highly degradeted urban landscapes.