title: Phylogenetic tests reject Emery's rule in the evolution of social parasitism in yellowjackets and hornets (Hymenoptera: Vespidae, Vespinae).
abstract: Social parasites exploit the brood-care behaviour and social structure of one or more host species. Within the social Hymenoptera there are different types of social parasitism. In its extreme form, species of obligate social parasites, or inquilines, do not have the worker caste and depend entirely on the workers of a host species to raise their reproductive offspring. The strict form of Emery's rule states that social parasites share immediate common ancestry with their hosts. Moreover, this rule has been linked with a sympatric origin of inquilines from their hosts. Here, we conduct phylogenetic analyses of yellowjackets and hornets based on 12 gene fragments and evaluate competing evolutionary scenarios to test Emery's rule. We find that inquilines, as well as facultative social parasites, are not the closest relatives of their hosts. Therefore, Emery's rule in its strict sense is rejected, suggesting that social parasites have not evolved sympatrically from their hosts in yellowjackets and hornets. However, the relaxed version of the rule is supported, as inquilines and their hosts belong to the same Dolichovespula clade. Furthermore, inquilinism has evolved only once in Dolichovespula.
authors.affiliation: Department of Biology , University of Vermont , Room 120A Marsh Life Science Building, 109 Carrigan Drive, Burlington, VT 05405, USA.
authors.forename: Federico
authors.initials: F
authors.lastname: Lopez-Osorio
authors.affiliation: Division of Invertebrate Zoology , American Museum of Natural History , Central Park West at 79th Street, New York, NY 10023, USA.
authors.forename: Adrien
authors.initials: A
authors.lastname: Perrard
authors.affiliation: Department of Biology , University of Vermont , Room 120A Marsh Life Science Building, 109 Carrigan Drive, Burlington, VT 05405, USA.
authors.forename: Kurt M
authors.initials: KM
authors.lastname: Pickett
authors.affiliation: Division of Invertebrate Zoology , American Museum of Natural History , Central Park West at 79th Street, New York, NY 10023, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Carpenter
authors.affiliation: Department of Biology , University of Vermont , Room 120A Marsh Life Science Building, 109 Carrigan Drive, Burlington, VT 05405, USA ; Department of Entomology , National Museum of Natural History, Smithsonian Institution , Washington, DC 20004, USA.
authors.forename: Ingi
authors.initials: I
authors.lastname: Agnarsson
keywords: Emery's rule; Vespinae; phylogeny; social insects; social parasitism