Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Abstract

Exotic species dominate many communities; however the functional significance of species' biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.

Climate modifies response of non-native and native species richness to nutrient enrichment

“…In particular, fewer native species were lost in response to nutrient addition in warmer, wetter sites. This is contrary to previous findings that suggest that nutrient enrichment reduces native species richness and increases non-native species richness independently of climate [10,39]. Rare species tend to be lost from communities with nutrient enrichment (particularly N) [8].…”

“…Under nutrient enrichment, changes in abundance and richness of native and non-native species were more related to annual climate, whereas under ambient conditions, longterm climate variables were better predictors. Previous studies across these grassland communities have shown that exotic species are more likely to have annual life histories than native species [39]. Furthermore, nutrient enrichment also increases the abundance of non-native species [7,39].…”

“…These mechanisms are not mutually exclusive, and most likely a combination of these mechanisms is acting across these grassland communities, weakening the negative effect of nutrient enrichment on the change in native species richness. Diversity across plant communities worldwide is decreasing with nutrient enrichment, often benefiting non-native species [8,39]. However, across a wide range of communities, nonnative species display a wide range of ecological strategies [17] that, depending on local environmental conditions, can lead to different competitive outcomes in their interaction with native species [18], not only to native species loss.…”

“…However, nutrient addition modifies environmental conditions, changing the composition of communities and reducing species diversity [4,5,8], often causing losses of rare, native, perennial and N-fixing species [8,39]. Thus, eutrophication represents a new filter, which modifies the identity and abundance of species in communities by selecting for a different combination of rstb.royalsocietypublishing.org Phil.…”

Are dominant plant species more susceptible to leaf‐mining insects? A case study at Saihanwula Nature Reserve, China

“…Dominant species are the small number of species that significantly affect other species (McNaughton & Wolf, 1970; Whittaker, 1965). Due to their high biomass, large size, high productivity, and other traits (Bouchenak‐Khelladi, Slingsby, Verboom, & Bond, 2014; Collins & Duffy, 2016), they can change environmental conditions and resource availability and thus shape community structure (Frieswyk, Johnston, & Zedler, 2007; Okullo, Greve, & Moe, 2013), community diversity (Kunte, 2008; Okullo et al., 2013), community phylogeny (Chalmandrier, Münkemüller, Lavergne, & Thuiller, 2015), trophic structure (Miller, Brodeur, Rau, & Omori, 2010), and ecosystem functions (Behera et al., 2017; Furey, Tecco, Perez‐Harguindeguy, Giorgis, & Grossi, 2014; Grime, 1998; Mokany, Ash, & Roxburgh, 2008; Seabloom et al., 2015). Both dominant species and keystone species are functionally important, but keystone species are much less abundant (Christianou & Ebenman, 2005; Hurlbert, 1997; Mouquet, Gravel, Massol, & Calcagno, 2013; Power et al., 1996).…”