Hybrid vigor and depression shouldn't occur just between different species or subspecies. The basic evolutionary unit is the population. In this case, we are crossing two different populations. That's why we call them F1.

I'm thinking of hybrid seed corn or any other commercial crop. Two varieties are constantly crossed to produce F1 hybrids. Further generations start to show hybrid depression. The two strains crossed certainly aren't different species or subspecies but just two different strains.

Whenever we cross two different populations, we should experience hybrid vigor and depression, just on a smaller scale. This should occur just by crossing anything from the northern and southern parts of a species range.

Is this thinking correct?

Norm Kopecky