Nephrolepis cordifolia is the species... Like many fern species, they are widespread. Many tropical/subtropical regions throughout the world. Probably some in south america. Your traditional 'Boston' type fern is also Nephrolepis cordifolia, I believe. Since they are so widely adaptable, I don't have a problem believing they are invasive. Although I'd be surprised if there wasn't some native variety of cordifolia already in habitat.
The particular form ('Duffii') may or may not be found in the wild. I don't know the origin, I suspect it was something somebody found in a collection one day and decided to propagate the tar out of it. Lemon Button is the common name, and common names are distressingly common... Might be a few things with that common name.