Tree Diversity Limits the Impact of an Invasive Forest Pest

• DOI: 10.1371/journal.pone.0136469
• Publication Date: 2015-09-11T18:00:25Z
• Authors: Virginie Guyot; Bastien Castagneyrol; Aude Vialatte; Marc Deconchat; Federico Selvi; Filippo Bussotti; Hervé Jactel
• Keywords: Sylviculture; 0106 biological sciences; 570; [SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture; Insecta; défoliation; Science; 577; herbivore; Leaf removal; lutte biologique; Horticulture; Forests; 01 natural sciences; communauté végétale forestière; Trees; [SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture, forestry; Sylviculture, foresterie; castanea sativa; Animals; guêpe; Herbivory; arbre forestier feuillu; Sweet chestnut (tree); [SDV.SA.HORT]Life Sciences [q-bio]/Agricultural sciences/Horticulture; mélange de variétés; Q; forestry; Dryocosmus kuriphilus; Comparative analysis; R; Trees, Chestnuts, Species Diversity, Shannon Index, Invasive Species, Forests, Plant-Herbivore interactions, Herbivory; Biodiversity; analyse comparative; 15. Life on land; italie; Italy; Medicine; essence forestière; foresterie; Introduced Species; Research Article

The impact of invasive herbivore species may be lower in more diverse plant communities due to mechanisms of associational resistance. According to the "resource concentration hypothesis" the amount and accessibility of host plants is reduced in diverse plant communities, thus limiting the exploitation of resources by consumers. In addition, the "natural enemy hypothesis" suggests that richer plant assemblages provide natural enemies with more complementary resources and habitats, thus promoting top down regulation of herbivores. We tested these two hypotheses by comparing crown damage by the invasive Asian chestnut gall wasp (Dryocosmus kuriphilus) on chestnut trees (Castanea sativa) in pure and mixed stands in Italy. We estimated the defoliation on 70 chestnut trees in 15 mature stands sampled in the same region along a gradient of tree species richness ranging from one species (chestnut monocultures) to four species (mixtures of chestnut and three broadleaved species). Chestnut defoliation was significantly lower in stands with higher tree diversity. Damage on individual chestnut trees decreased with increasing height of neighboring, heterospecific trees. These results suggest that conservation biological control method based on tree species mixtures might help to reduce the impact of the Asian chestnut gall.