Effects of Insect Herbivory on Bilberry Production and Removal of Berries by Frugivores

Abstract

The evolutionary purpose of a fleshy fruit is to attract seed dispersers and get the seeds dispersed by frugivorous animals. For this reason, fruits should be highly rewarding to these mutualists. However, insect herbivory can alter plant reproductive success e.g. by decreasing fruit yield or affecting the attractiveness of the fruits to mutualistic seed dispersers. Under natural conditions, we tested the effects of experimental larval-defoliation on berry ripening and consumption of a non-cultivated dwarf shrub, the bilberry (Vaccinium myrtillus L.), which produces animal-dispersed berries with high sugar and anthocyanin concentration. Bilberry ramets with high fruit yield were most likely to have their berries foraged, indicating that frugivores made foraging choices based on the abundance of berries. Moreover, the probability for berries being foraged was the lowest for non-defoliated ramets that grew adjacent to larval-defoliated ramets, even though larval-defoliation did not affect the biochemical composition (total concentrations of anthocyanins, sugars and organic acids) or the probability of ripening of berries. We hypothesise that the lower probability for berries being foraged in these ramets may be a consequence of rhizome- or volatile-mediated communication between ramets, resulting in a priming effect of the herbivore defence and lower attractiveness of the non-defoliated ramets.

Parasitoids of leaf herbivores enhance plant fitness and do not alter caterpillar‐induced resistance against seed beetles

“…Interactions among herbivores can occur between the earlier and final stages of plant development and indirectly affect the plant reproductive fitness. For example, leaf herbivory has been shown to reduce attack by florivores, seed predators and frugivores (Hernández-Cumplido, Glauser, & Benrey, 2016;Koski et al, 2017;McArt, Halitschke, Salminen, & Thaler, 2013), such that flowers, fruits and seeds of plants subjected to leaf herbivore damage are less vulnerable to subsequent attack by seed moths and beetles.…”