Overcompensating plants: their expression of resistance traits and effects on herbivore preference & performance

Background/Question/Methods

Overcompensation is an interesting plant tolerance response in which plants have higher fitness after herbivory than without damage. It is now broadly assumed that plants are able to simultaneously express resistance and tolerance traits but it is unclear if plants that overcompensate are also inducing resistance-mediating secondary metabolite production. Moreover, it is unknown how herbivores perform on plants that overcompensate. Our previous work has shown that certain potato varieties in Colombia can express overcompensatory responses to damage by the potato tuber moth.  Here we investigated (1) if potatoes that express overcompensatory responses also induce resistance traits and (2) how the potato tuber moth responds in terms of preference and performance to undamaged and previously induced plants. We determined the presence of secondary compounds and tested larval performance in tubers expressing overcompensatory responses in comparison to undamaged tubers. Ovipositing females were exposed to plants with and without potato tuber moths to determine their preference.

Results/Conclusions

Our results show that systemically induced tubers have not only a higher biomass, but also an increased amount of phenolic compounds and proteinase inhibitors. Tuber moth pupal weight increased with increasing tuber size, while changes in the tuber’s secondary metabolism did not seem to affect any metrics of larval performance. Oviposition preference did not change between induced and undamaged plants. Our data show that potato plants expressing overcompensatory responses also induce secondary compounds known to increase resistance against herbivores. Hypotheses for why larvae perform better in larger tubers and are not affected by the secondary metabolism are discussed. From an ecological and agricultural point of view our results suggest that the expression of overcompensatory traits could have positive effects on herbivore performance and this way exacerbate pest problems, but studies at a population level would be needed to evaluate this possible outcome.