After some reflection,(and consultation with "Ecology and Evolution of
Livebearing Fishes") I am of the opinion that there are "northern" and
"southern" population morphs of both Gambusia and Heterandria strains
with VERY DIFFERENT temperature tolerances.
I would bet good money, that if you got some H. formosa from say Miami,
FL...and put them in Moon`s Het. pond in Wilmington, N.C., that they
would go "belly-up" first good freeze.
Same with Gambusia strain (holbrooki and affins)...Miami and say New
Jersey.
Simply put, these fish have adapted to local climates through the ages.
And I think there is an incredible lack of knowledge and documentation
in this area, and with native fishes in general.
Rob
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