Facilitation cascade drives positive relationship between native biodiversity and invasion success

Abstract

Abstract. The pervasive impact of invasive species has motivated considerable research to understand how characteristics of invaded communities, such as native species diversity, affect the establishment of invasive species. Efforts to identify general mechanisms that limit invasion success, however, have been frustrated by disagreement between landscape-scale observations that generally find a positive relationship between native diversity and invasibility and smaller-scale experiments that consistently reveal competitive interactions that generate the opposite relationship. Here we experimentally elucidate the mechanism explaining the large-scale positive associations between invasion success and native intertidal diversity revealed in our landscape-scale surveys of New England shorelines. Experimental manipulations revealed this large-scale pattern is driven by a facilitation cascade where ecosystem-engineering species interact nonlinearly to enhance native diversity and invasion success by alleviating thermal stress and substrate instability. Our findings reveal that largescale diversity-invasion relationships can be explained by small-scale positive interactions that commonly occur across multiple trophic levels and functional groups. We argue that facilitation has played an important but unrecognized role in the invasion of other well studied systems, and will be of increasing importance with anticipated climate change.

Environmental stress, facilitation, competition, and coexistence

“…We speculate that Watersipora may mediate the negative effects of sedimentation on Bugula in harsh environments, perhaps by changing patterns of water flow via generation of feeding currents (Okamura 1985, Vogel 1994. That Watersipora can facilitate other species by at least two mechanisms is consistent with extensions of stress gradient models that highlight the role of foundation species for providing the physical context for community development, such that communities themselves are hierarchically organized (Bruno and Bertness 2001, Altieri et al 2010, Angelini et al 2011.…”

An experimental evaluation of the direct and indirect effects of endemic seaweeds, barnacles, and invertebrate predators on the abundance of the introduced rocky intertidal barnacle Balanus glandula

“…Competition for resources such as space (Stachowicz et al 2002) and food (Petren and Case 1996) can also reduce the chance of colonization by introduced species. Facilitation can sometimes act as a driver for successful invasion when it alleviates an environmental stress (Altieri et al 2010). In addition, such species interactions may play an important role on abundance via indirect effect (White et al 2006).…”

Large-scale facilitation of a sessile community by an invasive habitat-forming snail

“…When non-indigenous species invade new communities, they interact with and have effects on many resident species (Staehr et al 2000;Crooks 2009;Altieri et al 2010). Similar to any other ecological network of interactions, this leads to some residents being adversely affected while others benefit.…”