Facilitation promotes plant invasions and indirect negative interactions

Abstract

Numerous pressures influence the ecological capacity and health of drylands globally. Shrubs are often a critical component of these systems and can function positively as foundation species through facilitation of other species. Nonetheless, limited attention has been paid to the potential negative and indirect effects of shrubs. Here, we tested the hypothesis that plant facilitation can both accelerate the invasion process and amplify the negative effects of an invader on the native community. The invasive species Bromus madritensis ssp. rubens capitalized on facilitation by resident native shrub species. This in turn further degraded California mixed grasslands by negatively impacting other annual protégé plant species in these specific microhabitats. Indirect shrub‐mediated interactions were thus a critical component of the ecological community assembly processes, and this suggests that we need to move beyond pairwise interactions to more rapidly advance grassland management and restoration theory.

Niche partitioning overrides interspecific competition to determine plant species distributions along a nutrient gradient

“…values of d were positive or negative), those interactions involved the facilitation of a C4 native ( C. truncata ) by the exotics. Other studies have found facilitation of exotic species by natives (Lucero et al 2019, Cavieres 2021, Lortie et al 2021), an outcome predicted to increase as resources increase (Northfield et al 2018), although there are fewer examples of exotic species facilitating natives (Alba et al 2019, Wainwright et al 2019). While our findings suggest the potential for exotic species to facilitate the establishment of a native species, they also highlight the need for caution in interpreting the outcome of species interactions in heterogeneous landscapes.…”

“…values of d were positive or negative), those interactions involved the facilitation of a C4 native (C. truncata) by the exotics. Other studies have found facilitation of exotic species by natives (Lucero et al 2019, Cavieres 2021, Lortie et al 2021, an outcome predicted to increase as resources increase (Northfield et al 2018), although there are fewer examples of exotic species facilitating natives (Alba et al 2019, Wainwright et al 2019.…”

Interspecific facilitation favors rare species establishment and reduces performance disparities among adults

“…Species that deeply depend on facilitation can find their abundance limited by the availability of the habitat provided by their nurse plants. That might be an important factor explaining why species that rely more on facilitation are more locally rare than those that rely less on facilitation, a worldwide pattern linking facilitation and plant species coexistence (Soliveres et al, 2015a, but see Lortie et al, 2021; Lucero et al, 2021 or Vega‐Álvarez et al, 2019) for particular cases in which facilitation favors abundant species.…”

The Impact of Multiple Species Invasion on Soil and Plant Communities Increases With Invasive Species Co-occurrence

“…Looking at net effects, one invader can inhibit or facilitate another one ( Flory and Bauer, 2014 ; Kuebbing and Nuñez, 2016 ; Zhang et al, 2020 ). Likewise, the overall impact of multiple invaders on native biodiversity and soil functioning may result from facilitative (positive) interactions, whereby multiple species increase the magnitude of their combined effects as compared to their individual effect, or from competitive (negative) interactions, in which case the combined effects are weaker than a single-species effect ( Lortie et al, 2021 ). Interactions among multiple invaders can also be neutral, in which case their combined impact is negligible ( Kuebbing, 2014 ).…”