Invasion in space and time: non‐native species richness and relative abundance respond to interannual variation in productivity and diversity

Abstract

Ecologists have long sought to understand the relationships among species diversity, community productivity and invasion by non-native species. Here, four long-term observational datasets were analyzed using repeated measures statistics to determine how plant species richness and community resource capture (i.e. productivity) influenced invasion. Multiple factors influenced the results, including the metric used to quantify invasion, interannual variation and spatial scale. Native richness was positively correlated with non-native richness, but was usually negatively correlated with non-native abundance, and these patterns were stronger at the larger spatial scale. Logistic regressions indicated that the probability of invasion was reduced both within and following years with high productivity, except at the desert grassland site where high productivity was associated with increased invasion. Our analysis suggests that while non-natives were most likely to establish in species rich communities, their success was diminished by high resource capture by the resident community.

Origin Matters: Diversity Affects the Performance of Alien Invasive Species but Not of Native Species

“…Separating studies assessing the establishment phase from those assessing the build-up of local dominance of alien invasive plant species may at least partly explain the variation in the effect of native species richness on invasibility as revealed by observational studies. This is supported by Cleland et al (2004), who found that native and nonnative species richness were positively correlated, but correlations between native richness and the relative abundance of alien plant species were predominately negative. Other observational studies assessing the relationship between native diversity and performance of established invasive alien species at fine scale also revealed a negative relationship (Prieur-Richard et al 2000;Kolb et al 2002).…”

“…At low diversity, invasive alien species may be able to better exploit untapped soil resources than natives. In comparison with the high productivity of grassland plant assemblages in Europe, the annual productivity in experimental studies assessing the diversity-invasibility relationship in North American grasslands is considerably lower (e.g., ∼250 g/m 2 in Fargione et al 2003; 119-428 g/m 2 in Cleland et al 2004; ∼200 g/m 2 in Maron and Marler 2008). The higher annual productivity in our field experiment, compared with those reported in North American field experiments, is likely to reflect a general trend of higher productivity in Europe than in the mixed-grass prairie in the intermountain western United States, where our target native species have become invasive and where the parallel experiment by Maron and Marler (2008) was conducted.…”

Novel forests maintain ecosystem processes after the decline of native tree species

“…While regional richness has increased in Wisconsin, for example, local richness has declined in most sites because native species ranges are declining faster than introduced species ranges are expanding (Rooney and Waller 2008). Furthermore, if local richness does increase following invasion, declining evenness may cause diversity to decline if most introduced species tend to be rare (Cleland et al 2004). Thus, the local diversity of novel ecosystems is the product of simultaneous losses of native species and additions of introduced species and their respective abundances, and can be lower, higher, or unchanged relative to historical native ecosystems.…”

Non-Native Plants Disrupt Dual Promotion of Native Alpha and Beta Diversity

“…Although the presence of non-native species is often correlated with native diversity, the magnitude and direction of this relationship depend on the spatial scale of observation (e.g., Stohlgren et al 1999Stohlgren et al , 2002Fridley et al 2007;Sandel and Corbin 2010). In other words, native alpha (within-habitat diversity), beta (betweenhabitat diversity) and gamma (overall diversity integrating alpha and beta) diversities show different relationships with non-native species (e.g., Cleland et al 2004;Davies et al 2005). Despite considerable efforts to explain multi-scale effects of non-native species, the paucity of experimental evidence in the plant community assembly literature (Götzenberger et al 2012) has left it unclear what processes are responsible for these effects and to what extent these apparent effects are actually caused by nonnative species per se.…”