Still, have shortened growing seasons ever been invoked
before as a major selective pressure for evolving nitrogen-fixing
symbioses? Are they especially prevalent in arctic and high alpine
environments BRBR

Where do most lichens and root-nodule legumes live?
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)