The assembly on islands is based upon the characteristics of the gene/sourcepools on the mainland. Dispersal ability varies greatly between taxa and within taxonomic groups, but is predictable: birds, bats and flying insects often overrepresented, while amphibians are uncommon. -Salt tolerance is important if an organism is ‘non-volant’ (cannot fly). There is a crucial difference between dispersal and establishment. Establishment is what happens after they have dispersed and gotten to the island. Ability to disperse and the ability to establish breeding populations are different. good dispersal + broad tolerance + ability to rapidly reproduce= establishment success.