Yes they were.......................
I believe that the question refers to Australia and to the fact that it's been very isolated and that as a result it has developed a number of species which cannot be found anywhere else.
The series of events here would be 1. the geographical isolation of Australia. it separated from the other lands 99 million years ago and 2. the frequent changes in climate it experienced which led to population bottlenecks, for example it was initially very warn and then it experienced a colder period.
It would be primarily commerce that takes place "within states" that is not a power of Congress, since the main power of Congress in this regard is to regulate interstate commerce.
