Urbanization alters interactions between Darwin’s finches and Tribulus cistoides on the Galápagos Islands

Emerging evidence suggests that humans shape the ecology and evolution of species interactions. Islands are particularly susceptible to anthropogenic disturbance due to the fragility of their ecosystems; however, we know little about the susceptibility of species interactions to urbanization on islands. To address this gap, we studied how the earliest stages of urban development affect interactions between Darwin’s finches and its key food resource, Tribulus cistoides, in three towns on the Galápagos Islands. We measured variation in mericarp predation rates, mericarp morphology, and finch community composition using population surveys, experimental manipulations, and finch observations conducted in habitats within and outside of each town. We found that both seed and mericarp removal rates were higher in towns compared to natural habitats. We also found that selection on mericarp size and defense differed between habitats in the survey and experimental populations, and that towns suppo...