Biotic and abiotic influences on native and exotic richness relationship across spatial scales: favourable environments for native species are highly invasible

Abstract

Summary 1. Biological invasions threaten biodiversity, and understanding the factors that influence a community’s susceptibility to invasion informs both management of invasive species and conservation efforts towards promoting biodiversity. 2. In this study, we examined the native–exotic richness relationships (NERR) at two spatial scales and asked what variables mediate the relationship between native and exotic species richness in 1‐m2 plots among old fields. We also tested whether the favourable environment and spatial heterogeneity mechanisms alter the relationship between native and exotic richness. Additionally, we identified biotic, abiotic and landscape factors that accounted for patterns of exotic species richness across spatial scales, from 50‐m transects (i.e. local scales) to entire old fields (i.e. landscape scales). 3. We found that native and exotic richness were positively related at both local and landscape spatial scales, with the strength of their relationship greater at the landscape scale. In old‐field communities with lower foliar cover, native and exotic plant richness were negatively related across 1‐m2 plots, whereas in old fields with higher foliar cover, native and exotic plant richness were positively related across 1‐m2 plots. Overall, predictors of exotic species richness depended on spatial scale: at local scales, native plant richness, light and landscape factors accounted for most of the variation, but biotic factors alone accounted for most of the variation at the landscape scale. 4. Our findings suggest that fields favourable for native species are also suitable for exotic species, and management efforts towards exotic richness should be tailored to spatial scale.

Native–Exotic Species Richness Relationships Across Spatial Scales in a Prairie Restoration Matrix

“…Similar to previous studies, as spatial scale of measurement increased, the slope of the native–exotic richness relationship increased when all plots were examined (Fridley et al ; Chen et al ; Souza et al ). Our data may provide some evidence for consequential species interactions occurring between natives and exotics in this restoration environment.…”

Evaluating Hypotheses of Plant Species Invasions on Mediterranean Islands: Inverse Patterns between Alien and Endemic Species

“…The positive correlation between alien and native species richness is consistent with multiple previous large-scale observational studies (Knops et al, 1995;Robinson et al, 1995;Planty-Tabacchi et al, 1996;Levine and D'Antonio, 1999;Lonsdale, 1999;Levine, 2000;McKinney, 2002;Stohlgren et al, 2003Stohlgren et al, , 2006Souza et al, 2011;Blackburn et al, 2016). It is difficult to ascertain the full causal relationship between alien and native species distributions, as their apparent co-variation may be due to similar, independent reactions to the same factors, specifically favorable environmental conditions, adequate resources and fertile land, meaning the conditions good for native species are also good for alien species (Levine and D'Antonio, 1999;Stohlgren et al, 1999;Richardson and Pyšek, 2006).…”

Resource availability mediates the importance of priority effects in plant community assembly and ecosystem function

“…We selected plant species that were among the fifty most common species (cover and/or frequency) found in old fields near our site (Souza et al 2011a). Sixteen species were chosen to represent three functional groups: six grasses, six non‐ legume forbs, and four legumes (Table 1).…”