How did animals get to their present ranges? How did koalas get from Ararat to Australia, polar bears to the Arctic, etc., when the kinds of environment they require to live doesn't exist between the two points. How did so many unique species get to remote islands?
How were ecological interdependencies preserved as animals migrated from Ararat? Did the yucca an the yucca moth migrate together across the Atlantic? Were there, a few thousand years ago, unbroken giant sequoia forests between Ararat and California to allow indigenous bark and cone beetles to migrate?
Why are so many animals found only in limited ranges? Why are so many marsupials limited to Australia; why are there no wallabies in western Indonesia? Why are lemurs limited to Madagascar? The same argument applies to any number of groups of plants and animals.
Why is inbreeding depression not a problem in most species? Harmful recessive alleles occur in significant numbers in most species. (Humans have, on average, 3 to 4 lethal recessive alleles each.) When close relatives breed, the offspring are more likely to be homozygous for these harmful alleles, to the detriment of the offspring. Such inbreeding depression still shows up in cheetahs; they have about 1/6th the number of motile spermatozoa as domestic cats, and of those, almost 80% show morphological abnormalities. [O'Brien et al, 1987] How could more than a handful of species survive the inbreeding depression that comes with establishing a population from a single mating pair?