1) Genetic analysis. Like you didn't know this already.

2) Temperature tolerance. (G)rows or (S)urvives: frost, 50, 60, 70, 72, 74, 76, 80, 90
ALB will survive a frosted emerse tank, loses leaves but grow back.
WEN is killed with any ice on the water surface. Evolutionary adcantage to survive light frost emerse? self-heating?

3)