Optimal radial distance between zoos in a metapopulation network for each taxonomic class of terrestrial vertebrates.

Optimal radial distance between zoos, average probability of reaching the metapopulation size threshold within that radial distance, average number of zoos within radial distance and average number of zoos within radial distance that hold the threatened species. The optimal radial distance represents the distance needed to optimize the probability of reaching an average metapopulation size within the shortest possible distance between zoos (the metapopulation thresholds m are >50, >100 and >250 individuals). The column for “number of species in cluster” indicates the number of threatened species for which all ISIS zoos have at least m individuals.