"How would a hybrid be created in nature without human hands in there mucking things up?"
I expect it's as simple as an insect or the wind carrying pollen to a genetically compatible plant which then forms a seed that manages to grow. If the chromosome count is even, then the result is probably fertile and there you are. Or if it's the sort of plant that reproduces vegetatively as well as by seed, then it can form a distinct population. That's been a problem for the folks who work on the taxonomic classification of plants. It causes them to re-assign or re-classify plants on a regular basis
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