Speciation is troublesome, especially for creationists because they have been mislead that it works like this: One day a chicken laid an egg that hatched into a duck. Another chicken did the same thing. The two ducks then bred a new species. This sounds ridiculous and it is.
It works more like this: In a group of wild dogs, some were smaller than the others. They tended to pair off, creating even smaller dogs. Over time you had both big and small dogs. They could still interbreed, but it was awkward, so they avoided doing it. The small dogs wandered off to a new territory where there were lots of badgers to root out. They kept changing, making them better and better at badger hunting simply because the bad badger hunters starved to death and the good badger hunters had lots of food to raise large litters.
The big dogs kept changing independently. Eventually the big and small dogs got to a point where they could still interbreed but the offspring would be sterile (as horses and zebras are today). Eventually they could get to the point they could not and would not interbreed. So a new species gradually comes into being. Sometimes two or more species split off and replace the original species.~ Roedy (1948-02-04 age:69) Observation of evolution in the wild