Wild tobacco plants change their flowering traits to optimize their interactions with animals, Dartmouth biology professor Rebecca Irwin writes in a review published in Current Biology this month.
Irwin discusses a study by Kessler et al., who found that wild tobacco plants can change their flowering time to attract different pollinators and deter predators.
The same plant traits that attract beneficial pollinators, Irwin writes, can also draw damaging herbivores, while the traits that deter antagonists or predators may also deter pollinators.
Even more paradoxical are the pollinating herbivores that simultaneously help and harm plants. To take advantage of pollination by night-flying hawkmoths, wild tobacco plants have evolved to open their flowers at night. While pollinating the plant, hawkmoths deposit eggs, which consume their host as larvae.
Kessler et al. found that larvae-damaged plants begin to open their flowers in the morning, attracting hummingbirds instead of hawkmoths as pollinators. To further protect themselves, the plants also take on a more hummingbird-friendly flower shape and reduce their production of benzyl acetone, a compound that attracts hawkmoths.
Kessler et al. hypothesize that such adaptations may also be present in other plant species. They have pinpointed jasmonic acid (JA) as the hormone driving herbivore-induced changes and found that the application of JA to other plants’ wounds can induce similar changes.
Irwin writes that it is not clear why tobacco has evolved to suit a harmful pollinator if hummingbirds can do the job, but notes based on the evidence from Kessler et al. that hummingbirds may simply be less reliable than hawkmoths.