Urbanization alters ecological and evolutionary interactions between Darwin’s finches andTribulus cistoideson the Galápagos Islands

Emerging evidence suggests that urbanization shapes the ecology and evolution of species interactions. Islands are particularly susceptible to urbanization due to the fragility of their ecosystems; however, few studies have examined the effects of urbanization on species interactions on islands. To address this gap, we studied the effects of urbanization on interactions between Darwin’s finches and its key food resource, Tribulus cistoides , in three towns on the Galápagos Islands. We assessed the effects of urbanization on seed and mericarp removal, mericarp morphology, and finch community composition using natural population surveys, experimental manipulations, and finch observations. We found that both seed and fruit removal rates were higher in urban compared to non-urban populations in the natural and experimental populations, and that urbanization modified selection on mericarp size and defense. Urban environments supported smaller and less diverse finch communities than non-urban environments. Together, our results suggest that urbanization can dramatically alter ecological interactions between Darwin’s finches and T. cistoides , leading to modified selection on T. cistoides populations. Our study demonstrates that urban development on islands can have profound effects on the ecology and evolution of trophic interactions.