Florida was once at the bottom of an ocean. Our "Florida Native" plants came here by way of wind, birds, and other natural means. Plants that were here in the mid 1500's when Spanish settlers arrived are considered Florida native plants. "Exotics" are plants that have been introduced to our landscapes since then - brought in by nature or by man.
“Native Plants of Florida.” Guide to Florida Landscape Plants for the Southern Half of the Sunshine State, www.south-florida-plant-guide.com/native-plants-of-florida.html.