Tasek ("lake") Bera in Penninsular Malaysia is the home to a rather infamous plant: Cryptocoryne Xpurpurae var. purpurae ("PUR") which turned out to be a natural hybrid of C. griffithi and C. cordata cordata.
This then is a plant, clearly C. cordata except or one thing: the long tail on the flower. C. griffithi does not have this... so where did the tail on the flower come from? PUR? Or some other species?
It's not impossible that this cross could happen all the time but does not always manifest as the PUR phenotype. Perhaps some large number of these hybrids do not grow at all while others show only very minor difference from the parent plants.