Rapid establishment of species barriers in plants compared with that in animals

Speciation, the process by which new reproductively isolated species emerge from ancestral populations, results from the gradual accumulation of barriers to gene flow within genomes. To date, the notion that interspecific genetic exchange (introgression) occurs more frequently between plant species than animals has gained a strong footing in scientific discourse. By examining the dynamics of gene flow across a continuum of divergence in both kingdoms, we observed the opposite relationship: Plants experience less introgression than animals at the same level of genetic divergence, suggesting that species barriers are established more rapidly in plants. This pattern raises questions about which differences in microevolutionary processes between plants and animals influence the dynamics of reproductive isolation establishment at the macroevolutionary scale.