I did a bit of research on the toxic cane toad, and its introduction to Australia. Cool stuff. Seems the ones with longer legs are surviving better, and this trait is being passed along to their offspring.
Surely this isn’t an example of “evolution” of species, as you said earlier? You wouldn’t say that a short Pygmy and a tall Massai are different species? No, they’re both fully Homo sapiens, though they have different genetic features.