The ecology and evolution of seed predation by Darwin's finches on Tribulus cistoides on the Galápagos Islands

Predator-prey interactions play a key role in the evolution of species traits through antagonistic coevolutionary arms-races. The evolution of beak morphology in the Darwin’s finches in response to competition for seed resources is a classic example of evolution by natural selection. The seeds of Tribulus cistoides are an important food source for the largest ground finch species (Geospiza fortis, G. magnirostris, and G. conirostris) in dry months, and the hard spiny morphology of the fruits are a potent agent of selection that drives contemporary evolutionary change in finch beak morphology. Although the effects of these interaction on finches are well known, how seed predation affects the ecology and evolution of the plants is poorly understood. Here we examine whether seed predation by Darwin’s finches affects the ecology and evolution of T. cistoides. We ask whether the intensity of seed predation and the strength of natural selection by finches on fruit defense traits varies among ...