Living or having sustained life. Biotic interaction is a mutual or reciprocal interaction between living organisms, in which the distribution of one species is influenced by the distribution of other species. Biotic interaction can be within the same group, for example, competition, facilitation, and parasitism in plants, or between groups, as best exemplified by relationships in food webs: herbivory, predation, and symbiosis (Guisan et al. (2006) J. Appl. Ecol. 43). See Gaines in D. Sax et al. (2005) on what species invasions reveal about biotic interaction. Biotic potential is the maximum population that an area can support. As the local ecological system approaches the biotic potential of a site, local stability rises, but global sustainability falls; as the system develops feedback loops and complex interactions, it becomes better adapted to local conditions and more stable to local impacts. In the long run, conditions keep changing so that the system becomes sub-optimal to the changed conditions (O’Neill (2001) Ecology 82, 12). Biotic homogenization describes the process by which species invasions and extinctions increase genetic, taxonomic, or functional similarity; ‘evidence is growing that changes in land cover are likely to be accompanied by the ongoing homogenization of biotas, and processes in which native species are replaced by a relatively small set of alien species (Gaston and Fuller (2007) PPG 31, 2). See Cassey et al. (2008) J. Biogeog. 35, 5.