The criteria for the selection of species under ex-situ conservation is/are

The criteria for the selection of species under ex-situ conservation is Vulnerability of the species to extinction.
Ex-situ conservation means, "off-site conservation". It is the process of protecting an endangered species, variety or breed, of plant or animal outside its natural habitat.
Ex-situ management can occur within or outside a species' natural geographic range. Individuals maintained ex-situ exist outside an ecological niche.
Ex-situ conservation, while helpful in humankind's efforts to sustain and protect our environment, is rarely enough to save a species from extinction.