What if there were an apocalypse looming and the decision on which animals to save was all up to you?  What if you only had time and space to save a few dozen species?

I admit, my first inclination would be a selfish one, to save dogs, horses, tigers, goats, wolves, whales, elephants, and wild birds because I enjoy them,  plus cows and chickens because I like milk and eggs.  But what about the survival of the planet and how animals would serve the new ecosystem?  What justifies saving predators?  Would we need to keep rodents and cockroaches around for some reason?  Snakes? Spiders? Mosquitoes?