Origin of Plant Hybrid Incompatibility

Abstract

Hybrid incompatibility (HI) can cause inviability or sterility of inter‐ or intra‐species hybrids, which hinders gene flow between populations and thus contributes to speciation. HI clearly reduces fitness, but is extremely common across kingdoms. The classic Bateson–Dobzhansky–Muller model suggests that HI is caused by the genic conflicts between independently evolved loci. In this case, HI is simply a by‐product of evolution and has never been selected against. This model is supported by dozens of empirical studies and many incompatible HI‐causal genes have been cloned in recent decades. The HI‐causal genes are usually hyper‐polymorphic and evolve rapidly. Genetic drift, selection and the coevolution of plants with external microbes, or with internal selfish elements, may have driven the evolution of HI. These findings greatly broaden our understanding of the origin of HI. Key Concepts Hybrid incompatibility is caused by the deleterious interactions between incompatible genes that evolved independently. Hybrid incompatibility is a by‐product of evolution. Co‐evolution of plants and their external or internal factors, such as pathogens and genetic selfish elements, drives the evolution of hybrid incompatibilities in plants. The causal genes of hybrid incompatibilities is predictable. Hybrid incompatibility causal genes are rapidly evolved. Some hybrid incompatibility causal genes are selected. Gene duplication play important roles for the evolution of hybrid incompatibility.