canyon,
I agree with the article. Gambusia shouldn't be stocked outside their native range. I would take this as far as to say that G. affinis shouldn't be stocked in the range of G. holbrooki and that P. kadiakensis shouldn't be stocked in the range of P. Paludosis. Neither of the entire grouping should be stocked where they would be outside their native range. All of these reproduce very well and they can not be eradicated easily from waters that can support them.
With regard to Kansas, the Genie is out of the bottle and they are almost ubiquitous. Same thing can be said about LMB. If there are gambusia in the creek, they will find their way into your pond eventually.
According to
NAS.USGS.gov they have populations in Michigan and Lake Michigan as well.
