Originally Posted by Himiko
Explain the species Culex molestus (mosquito, evolved in the London Underground), Helacyton gartleri (bacterial, from a human carcinoma - that is, human cells), or several others in plant life created from polyploidy. Oh, for that matter, while not directly observed, several environments only formed in recent times show new species not observed before (Mimulus species of fish in copper-high water draining from mines, Cichlids in Lakes Malawi and Victoria), or the growing inability to breed between certain subspecies that are divided by methods evolution states would aid and accelerate speciation, such as silverside fish between marine and estuarine, or the apple maggot fly, which is dividing between the Hawthorn apples and certain introduced domestic apples.
Oh, and you're assuming that there is a spontaneous generation of one species from another, not a gradual shift due to accumulating differences from natural selection (microevolution). Also, hermaphroditic and asexual species don't suffer from this limitation.