they really knew their pokemon's moves even though they came from diffrent islands
While there were a couple of trades in the anime, the writers realized that it would be ridiculous to have Pokemon trade-evolve like in the games. Why? Because that would mean having to give your Pokemon to someone, and by doing this, what's they say they wouldn't take the Pokemon and run? The writers came up with an idea that using the Pokemon center teleport system would work like trading(they did this before, with Misty's Poliwhirl).Actually it taught us again that anime Pokemon don't evolve by trading.