Characterization of Arabidopsis thaliana regrowth patterns suggests a trade-off between undamaged fitness and damage tolerance

Herbivory is a fundamental type of plant-animal interaction that presents substantial selection pressure on plants to replace lost tissues and to prevent subsequent losses in fitness. Apical herbivory, which entails removal or damage to the apical meristem, causes a change in plant architecture by disrupting the balance of hormones produced in part by the apical meristem. Therefore, for an annual semelparous plant, the ability to preserve reproductive success following damage (i.e., to tolerate damage) is largely dependent on the plant's pre-damage investment into fitness and its regrowth pattern following damage. Using multiple regression analyses, we assessed the relationship of developmental and architectural traits of experimentally damaged plants relative to undamaged plants of 33 Arabidopsis thaliana genotypes that display a wide range of undamaged fitness and damage tolerance. Our analyses revealed evidence for an evolutionary bet-hedging strategy within a subset of genotypes to presumably maximize fitness under natural herbivory-genotypes with the greatest seed production when undamaged exhibited a significant reduction in seed yield when damaged, while genotypes with low undamaged seed production were the only genotypes whose seed yield increased when damaged. Patterns of endopolyploidy paralleled those of seed production, such that the increase in whole-plant ploidy by genome re-replication during growth/regrowth contributes to undamaged fitness, damage tolerance, and their trade-off. Overall, this study provides the first large-scale characterization of A. thaliana regrowth patterns and suggests that investment into fitness and endopolyploidy when undamaged may come at a cost to tolerance ability once damaged.