A few years ago, I have seen a documentary film about a plant in
Hawaii, I could not remember it's name, but it looked like a weed that
most people would not bother about it. This plant has quickly spread
to locations at various altitudes with climatic differences, and
therefore each plant has evolved into a different variation that
superficially looked very different from the original plant. I also
recall that the diverged species could be crossbred, because there was
not enough time to make genetic divergence, but I did not see how the
hybrid species would look like.

Maybe the data I'm providing is not enough to give a hint to the
species I'm inquiring about, but I can give you an example from the
world of cacti, with which I'm much more familiar: Most cacti can be
grafted on other types of cacti, because they are closely related,
although they look quite different: The ribbed structure of ferocacti,
the radiating shape of Mamillarias, the star-shaped Ariocarpus, and
the columnar Quiabentia which still carries leaves. If we
crosspolinate two different cacti and obtain viable seeds, how would
the hybrid look like ? Is there an example of such a plant I would
find i the market ?