Positive interactions and coexistence in diverse communities
Relative to food webs, we still know relatively little about the diversity and strength of non-feeding interactions in natural communities. We investigated the non-trophic interactions in a rocky intertidal community and found evidence that coexistence is mediated by reciprocal positive effects between a sub-dominant algal turf and the kelp canopy (Barner, et al. 2106. Journal of Ecology). This study confirms theoretical expectation that recruitment facilitation can mediate coexistence among competitors and demonstrates that positive feedback loops, though rare, may persist in natural systems.
Beyond our study, however, in global kelp forests understory algae are thought to have universally negative impacts on kelp. My current work explores the empirical evidence underlying this dominant paradigm and the implication of positive kelp-macroalgal interactions for regime shifts.