The existence of reproductive isolation, so that these situations can not occur, even if there are some individuals of different species sometimes complete the mating, but they generally can not produce offspring, or produce offspring can not continue to reproduce
Researchers believe that the longer a female fly killed by a fungal infection dies, the greater the spread of these fungi, releasing more chemical signals
The primitive food chain is mutually exclusive, so that different species can continue to survive in nature, piranhas have a nemesis even if they are fierce.