A fungal endophyte alters poplar leaf chemistry, deters insect feeding
and shapes insect community assembly
Abstract
The endophytic fungi of certain grasses and other herbaceous plants have
long been known to provide plants with anti-herbivore defense compounds,
but there is little information about whether the endophytes of trees
also engage in such mutualisms. We investigated the influence of the
endophytic fungus Cladosporium cladosporioides on the chemical defenses
of black poplar (Populus nigra) trees and the consequences for feeding
preference and fitness of herbivorous insects and insect community
assembly. Endophyte colonization increased both constitutive- and
induced poplar defenses. Generalist Lymantria dispar larvae preferred
and performed better on uninfected over endophyte-infected poplar
leaves, most likely due to higher concentrations of salicinoids in
endophytic leaves and the endophyte-produced alkaloid stachydrine. Under
field conditions, the endophytic fungus also shapes insect community
assembly in young black poplar trees. Our results show that endophytic
fungi can play a major role both in defending trees against herbivorous
insects and in structuring insect communities.