Irreversible evolution of plant mating system easily triggered by pollinator declines

The reversibility or irreversibility of evolution is a long-standing question in evolutionary biology.It is receiving renewed interest in the context of the ongoing human-induced environmental changes, as the answer determines the extent to which human impacts may be permanently altering the evolutionary trajectories of natural populations.Here, I show through a mathematical model that evolutionary irreversibility is likely common in nature, when selection acts on the absolute value of traits.Applied to the mating system of flowering plants, I predict that plant evolution towards self-pollination driven by pollinator declines frequently presents a tipping point after which reversibility is impossible, even if pollinator populations are subsequently restored to their highest levels.These results provide a microevolutionary explanation for the commonly observed macroevolutionary pattern of irreversibility of the evolution towards selfing in flowering plant lineages.They further suggest that ongoing global changes may already have long-term evolutionary repercussions, and highlight the urgency of preventing further impacts where still possible.