DOI: 10.5061/dryad.7950f
title: Data from: The complex net effect of reciprocal interactions and recruitment facilitation maintains an intertidal kelp community

description: 1.Theoretical and empirical ecology has transitioned from a focus on the
 role of negative interactions in species coexistence to a more pluralistic
 view that acknowledges that coexistence in natural communities is more
 complex, and depends on species interactions that vary in strength, sign,
 and reciprocity, and such contexts as the environment and life history
 stage. 2. We used a whole-community approach to examine how species
 interactions contribute to the maintenance of a rocky intertidal
 macroalgal canopy-understorey assemblage. We determined both the types of
 interactions in this network, and whether interactions were sensitive to
 environmental gradients. 3. Focusing on a structurally dominant canopy
 kelp Saccharina sessilis, and its diverse co-occurring understorey
 assemblage, we evaluated the role of the understorey in controlling S.
 sessilis recruitment and quantified the reciprocal effect of the S.
 sessilis canopy and understorey on one another using a removal experiment
 replicated across 600 km of coastline. We determined the sensitivity of
 interactions to natural variation in light and nutrient availability
 (replicated among four regions on the N.E. Pacific coast), and under
 different wave conditions (three wave regimes). 4. Surprisingly, species
 interactions were similar across sites and thus not context-dependent.
 Unexpectedly, the understorey community had a strong positive effect on
 the S. sessilis canopy, whereby the adult canopy decreased dramatically
 following understorey removal. Additionally, S. sessilis recruitment
 depended on the presence of understorey coralline algal turf. In turn, the
 canopy had a neutral effect on the coralline understorey, but a negative
 effect on non-calcifying algal turfs, likely eventually generating
 positive indirect canopy effects on the coralline understorey.
 Density-dependent intra-specific competition between S. sessilis adults
 and recruits may moderate this positive feedback between the S. sessilis
 canopy and coralline understorey. 5. Synthesis. Our research highlights
 the importance of positive interactions for coexistence in natural
 communities, and the necessity of studying multiple life-history stages
 and reciprocal species interactions in order to elucidate the mechanisms
 that maintain diversity.
description: Species
 NamesNames for all the
 species in both experiments and the abbreviated name found in the other
 data files.species_names.csvRecruitment ObservationsData for observational recruitment surveys in 2010 and 2012. Each row are the number of Saccharina sessilis recruits found on the substrate listed in the "Substrate" column, within a 0.25 cm2 quadrat.recruitment_observations.csvRegional Interaction ExperimentData for the regional interaction experiment (2008-2009). Each row is a single experimental plot, identified by Site, Cape, Treatment ("Trt") and the replicate ("Rep). Following these 4 plot identifiers are the estimated abundance of each species in plot at the end of the experiment (2009).regional_interaction_experiment.csvWave Exposure ExperimentData from the wave exposure experiment (2012-2013). Unlike regional interaction experiment, these data are repeated measures, where the abundance of species was measured at each time point listed in "Date". After 8 plot identifiers (using the same categories as in the regional interaction experiment), the abundance of each species is listed in wide format.wave_exposure_experiment.csv