Biological invasions by alien species (in this context, species transported by human actions to areas in which they do not naturally occur) represent one of the primary ways in which people are changing global biodiversity. Native species richness is a positive function of geographic area - the well-known species-area relationship.
An interesting question is whether alien species recapitulate this pattern, broadly and/or in detail. Here, we review the increasing body of research exploring alien species richness in the context of geographic area.
We assess both the similarities and differences between the species-area relationships of alien and native species groups and how adding alien species to areas affects the overall species-area relationship. Then, we assess how analysis of data for alien species informs our understanding of the mechanisms controlling species-area relationships more generally.
We finish with some broad conclusions on the basis of the previous sections.