Just curious, have you done any genetic analysis of the newly-developed populations? It seems like that would be a pretty good way to figure out if the expansion is absolutely natural or if the populations are introduced through bait buckets and stuff like that. Based on the pattern I would guess it's natural but you clearly have more experience with these guys than I do! If as it turns out that all the new frogs have genetic markers from a population 300 miles south where a bait fishery is located then it'd be good to know