Consumer-resource interactions along urbanization gradients drive natural selection

Area of Science:

• Ecology
• Evolutionary Biology
• Urban Ecology

Background:

• Urbanization is a major driver of global environmental change.
• Urban ecosystems often exhibit altered species interactions, including the loss of high-trophic-level species.
• The evolutionary consequences of these urban-induced ecological shifts are understudied.

Purpose of the Study:

• To investigate the evolutionary effects of species loss in urban environments.
• To examine how urbanization influences natural enemy communities and selective pressures.
• To test for local adaptation in a species experiencing divergent selection along urbanization gradients.

Main Methods:

• Studied the gall-forming fly (Eurosta solidaginis) and its natural enemies across five urbanization gradients.
• Assessed changes in enemy populations (birds, parasitoids) and their selective impacts on gall size.
• Quantified selection patterns and phenotypic variation in relation to urbanization levels.

Main Results:

• Urbanization led to a decline in the fly population and its bird predators, which target larger galls.
• A parasitoid attacking smaller galls was unaffected by urbanization.
• Urban areas exhibited stronger directional selection and a loss of stabilizing selection on gall size.

Conclusions:

• Urbanization can reshape natural selection by altering predator-prey interactions.
• Despite divergent selection, adaptive divergence in gall size was not conclusively demonstrated, possibly due to environmental factors, gene flow, or drift.
• The evolutionary impacts of urbanization on species interactions and selection are predictable and significant.