Data and R code from: Pollination interactions reveal direct costs and indirect benefits of plant–plant facilitation for ecosystem engineers

Ecosystem engineers substantially modify the environment via their impact on abiotic conditions and the biota, resulting in facilitation of associated species that would not otherwise grow. Yet, reciprocal effects are poorly understood as studies of plant–plant interactions usually estimate only benefits for associated species while hardly considering how another trophic level may mediate direct and indirect effects for ecosystem engineers. We run a field experiment with ecosystem engineers blooming either alone or with associated plants to decompose net effects and to test the hypothesis that pollinator-mediated interactions provide benefits which balance costs of facilitation by ecosystem engineers. We found that net costs of facilitation are accompanied by pollinator-mediated benefits. Despite ecosystem engineers producing less flowers per plant, they were visited by more and more diverse pollinators per flower when blooming with associated plants than when blooming alone. However, fruit set was unaffected by the presence of associated plants and seed production per plant was higher when ecosystem engineers bloomed alone. Our findings suggest that besides experiencing direct costs, ecosystem engineers can also benefit from facilitating other species via increasing their own visibility to pollinators. This study illuminates how the outcome of direct plant–plant interactions might be mediated by indirect interactions including third players.