title: Sweet Tetra-Trophic Interactions: Multiple Evolution of Nectar Secretion, a Defensive Extended Phenotype in Cynipid Gall Wasps.
abstract: Many herbivores employ reward-based mutualisms with ants to gain protection from natural enemies. We examine the evolutionary dynamics of a tetra-trophic interaction in which gall wasp herbivores induce their host oaks to produce nectar-secreting galls, which attract ants that provide protection from parasitoids. We show that, consistent with other gall defensive traits, nectar secretion has evolved repeatedly across the oak gall wasp tribe and also within a single genus (Disholcaspis) that includes many nectar-inducing species. Once evolved, nectar secretion is never lost in Disholcaspis, consistent with high defensive value of this trait. We also show that evolution of nectar secretion is correlated with a transition from solitary to aggregated oviposition, resulting in clustered nectar-secreting galls, which produce a resource that ants can more easily monopolize. Such clustering is commonly seen in ant guard mutualisms. We suggest that correlated evolution between maternal oviposition and larval nectar induction traits has enhanced the effectiveness of this gall defense strategy.
authors.forename: James A
authors.initials: JA
authors.lastname: Nicholls
authors.forename: George
authors.initials: G
authors.lastname: Melika
authors.forename: Graham N
authors.initials: GN
authors.lastname: Stone
mesh_terms: D000818:Animals; D005260:Female; D006790:Host-Parasite Interactions; D010641:Phenotype; D057048:Plant Nectar; D029963:Quercus; D014863:Wasps
chemical_list: D057048:Plant Nectar
keywords: Cynipini; Disholcaspis; coevolution; defensive trait; nectar secretion; trophic interactions