title: Insect herbivores should follow plants escaping their relatives.
abstract: Neighboring plants within a local community may be separated by many millions of years of evolutionary history, potentially reducing enemy pressure by insect herbivores. However, it is not known how the evolutionary isolation of a plant affects the fitness of an insect herbivore living on such a plant, especially the herbivore's enemy pressure. Here, we suggest that evolutionary isolation of host plants may operate similarly as spatial isolation and reduce the enemy pressure per insect herbivore. We investigated the effect of the phylogenetic isolation of host trees on the pressure exerted by specialist and generalist enemies (parasitoids and birds) on ectophagous Lepidoptera and galling Hymenoptera. We found that the phylogenetic isolation of host trees decreases pressure by specialist enemies on these insect herbivores. In Lepidoptera, decreasing enemy pressure resulted from the density dependence of enemy attack, a mechanism often observed in herbivores. In contrast, in galling Hymenoptera, enemy pressure declined with the phylogenetic isolation of host trees per se, as well as with the parallel decline in leaf damage by non-galling insects. Our results suggest that plants that leave their phylogenetic ancestral neighborhood can trigger, partly through simple density-dependency, an enemy release and fitness increase of the few insect herbivores that succeed in tracking these plants.
authors: University of Rennes 1/Centre National de la Recherche Scientifique, Research Unit UMR 6553, « Ecosystems, Biodiversity, Evolution», Campus Beaulieu, Bâtiment 14 A, 263 Av. du Général Leclerc, 35042, Rennes Cedex, France, benyguel@hotmail.fr.
authors: Benjamin
authors: B
authors: Yguel
authors: Richard Ian
authors: RI
authors: Bailey
authors: Claire
authors: C
authors: Villemant
authors: Amaury
authors: A
authors: Brault
authors: Hervé
authors: H
authors: Jactel
authors: Andreas
authors: A
authors: Prinzing
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005602:France; D060434:Herbivory; D006927:Hymenoptera; D007915:Lepidoptera; D010802:Phylogeny; D010944:Plants / Q000145:classification; D029963:Quercus / Q000145:classification*; D014197:Trees / Q000145:classification