Short answer: You can, but you shouldn't.

Long answer: Poloniex is one of the exchanges that have agreed to distribute ARDR to their users. But there are many possibilities it could go wrong. NXT on an exchange are only IOUs, and ARDR assets are the same. So if the exchange goes bankrupt (until October it's much time in the altcoin exchange world) you wouldn't see anything.

Another possible problem is that if you trade the NXT in the snapshot period, then it is possible that the exchange will calculate the ARDR the wrong way. That must not even be caused by bad intentions: Let's suppose you have a trading bot that trades small price swings, and it just happens that at most of the hourly snapshot intervals you are "in fiat". The exchange could then say "Ah, but you didn't have NXT at the moment of the hourly snapshot.", and they would be totally right to not distribute you the amount of ARDR you expected.