Hawaiian seedlings fail to recover from simulated herbivory

Herbivory is a key threat to seedlings, driving plant community composition and the evolution of seedling defences. In Hawaii, seedling herbivores are not part of the native fauna, but have recently become prevalent due to invasions of herbivorous molluscs and mammals, which target native Hawaiian seedlings.

Mean levels of tolerance, quantified as the ratio of damaged/control plant means, for lobeliad species in the Campanulaceae family compared with all other species. The data are species-level means, with n = 4 for lobeliads and n = 5 for non-lobeliads. Bars are means ± 1 s.e. Image by Barton (2016).

Using a greenhouse experiment, Barton found that Hawaiian seedlings have limited compensatory growth following simulated herbivory despite demonstrating induced shifts in photosynthesis and biomass allocation to roots vs. shoots. Ultimately, this led to low tolerance across the entire group of ten species. Species in the Campanulaceae were particularly intolerant of seedling damage due to high rates of non-photochemical quenching.