Seems to me that the existence of so many highly similar species is the evidence for this theory
What sort of evidence would one need to satisfy you?
How about leaving animals on an island and watching them for several hundred years to see if they change into a new species?...
madegascar, anyone? the first part of arguing evolution is the acknowledgment of the age of the planet and the time frames proposed by the theorists in the first place. you're not talking about evolution here with your 'few hundred years'; you're talking about a miracle. indeed, as you said, one would have to be quite faithful to believe that the bizarre creatures on madegascar, for example, diverged to their state in a few hundred or even thousand years. what requires less faith, is the recognition that during the time these populations were isolated from the mainland of africa, they evolved. as much is evidenced by their uniqueness to the island, genetic roots to mainland creatures, and convenient adaptation to the habitat they live.
funny you mention islands, that's where the argument for evolution speaks loudest. try 150,000,000 years of isolation in madegascar's case.
Are these 'new' species or the remnants of species that were killed off on the continent?
Evolutionists always want to scoff when asked for evidence, and try to blow fluff about how they don't know how long it would take or saying that creationalists are being extreme for asking for examples of species changing into other species. Then they turn right around and teach impressionable children that they originally crawled out of some primordial 'soup' and evolved into vertebrae animals, and then mammals, and then ape-like creatures to neanderthals and eventually 'evolved' into men.
Surely if 'evolution' is as common to life as you came, there would be some evidence. Instead, all you can demonstrate is 'selective breeding' (geographics or men choose the survivors, so that some traits change) has changed a 'few' animals. According to the 'beliefs' of evolutionists, we should be continually evolving, and should see a difference. Instead, amoebas are still amoebas, and apes are still apes. They have not changed in the thousands of years we have watched them.
Just admit that 'evolution' is a religion (a bigoted religion), that believes that all doubters must be converted to the faith.