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Sofia Carvajal-Endara

Evaluating the effect of seed predation by Darwin’s finches on seed and plant community structure
Sofia Carvajal-Endara, Luis Fernando De León, Jonathan Davies, and Andrew Hendry
MCGILL UNIVERSITY

The availability of food in the Galápagos archipelago has shaped the evolution of Darwin’s finches and thus their adaptive radiation. Most species of Darwin’s finches are generally opportunistic, using food resources according to their availability; yet differences in diet emerge during dry conditions, when predation pressure increases and commonly preferred resources become scarce. Although the production and availability of seeds is strongly influenced by climatic factors, it has been suggested that seed predation could change the distribution of seeds and therefore the composition of plant community. To disentangle the effects of finch seed predation from other processes shaping plant assemblages, we use a exclosure experiment, where seed predation by Darwin’s finches was removed, to directly test the effect of predation on plant communities. 25 paired exclosure and control plots where placed at two sites in Santa Cruz Island, and the seed and plant composition of each plot was surveyed over four years. If predation has a strong effect on seed and plant communities we would expect that communities without predation show (1) higher seed and plant diversity; (2) more overdispersed phylogenetic structures, given that under strong predation pressure usually seeds with similar defense traits will survive. So far, our results suggest that seed predation might have a strong effect on seed diversity but the effect on phylogenetic structure of seeds and plant communities seems to be context dependent