The species-area relationship (SAR) is one of the most general patterns in ecology. Recently, SARs have been employed as tools for comparing the ecology and biogeography of native and exotic species across spatial scales and exploring the influence of invasive species on native biodiversity. Here, we assess published studies to determine if SARs differ between native and exotic assemblages. We conducted a literature search to find studies that estimated the exponent (z) of the power-law SAR for native and exotic species across the same set of locales. We also compiled intercepts (c) of SARs where available. We used linear mixed models to test if z and c differed between native and exotic species and if this relationship differed across taxa. Our literature search produced 40 native-exotic pairs from 25 studies with which to compare the exponent of the power-law SAR. Further, 20 studies reported SAR intercepts.
Results/Conclusions
Overall, exotic SAR exponents (z) did not differ from those of natives. This trend was consistent for plants, birds, and animal assemblages. However, native bird SARs had marginally greater z values than exotic bird SARs. The intercepts (c) of native SARs were significantly greater than those of exotics for all taxonomic groups combined, but native SAR intercepts were not significantly greater than exotics for birds and animals. Our results suggest processes driving the increase in species richness with area are similar for native and exotic species. Expanding studies that compare SARs of native and exotic species to more taxonomic groups and different types of SARs (e.g., nested, contiguous, non-contiguous) will facilitate a better understanding of how native and exotic species richness scale with area.