“Congratulations, it’s a stunted, malformed, necrotic hybrid!” Those aren’t really the words that new parents want to hear but thankfully, plants aren’t in a position to be that upset.

In several species of plants, a surprising number of offspring turn out to be malformed hybrids that quickly wither and die. Now, Kirsten Bomblies and colleagues from the Max Planck Institute for Developmental Biology have found out why.

Two genes, one passed down by each parent, ignite an reaction in the hybrid youngster that turns its immune system against it. It’s not a genetic disorder; neither gene was faulty and both were harmless in their native parental environments. But they evolved apart from each other and make poor bedfellows when united.

They behave