Positive and Negative Interactions Control a Facilitation Cascade 1,2, 3 1,2,4 3 3 PAUL E
Positive and negative interactions control a facilitation cascade 1,2, 3 1,2,4 3 3 PAUL E. GRIBBEN, DAVID L. KIMBRO, ADRIANA VERGES , TARIK C. GOUHIER, SAMUEL BURRELL, 1,3 1 1 2,4 RUBY G. GARTHWIN, MARIA LASTRA CAGIGAS, YASMIN TORDOFF, AND ALISTAIR G. B. POORE 1Centre for Marine Bio-Innovation, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052 Australia 2Sydney Institute of Marine Science, 19 Chowder Bay Road, Mosman, New South Wales 2088 Australia 3Northeastern University Marine Science Centre, 430 Nahant Road, Nahant, Massachusetts 01908 USA 4Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052 Australia Citation: Gribben, P. E., D. L. Kimbro, A. Verges, T. C. Gouhier, S. Burrell, R. G. Garthwin, M. L. Cagigas, Y. Tordoff, and A. G. B. Poore. 2017. Positive and negative interactions control a facilitation cascade. Ecosphere 8(12):e02065. 10.1002/ ecs2.2065 Abstract. Facilitation cascades, which enhance the diversity of ecological communities in many ecosys- tems, have been viewed as the net outcome of positive species’ interactions. The strength and direction of these interactions, and thus the realized biodiversity, however, are likely to vary with the density and traits of the habitat-formers and via negative interactions among interacting species. To test this, we manipulated the density and status (alive vs. dead) of a secondary habitat-former, the razor clam Pinna sp., and mea- sured responses by the primary habitat-former, the seagrass Zostera muelleri, associated epifauna and infauna, and fish foraging behavior.