title: Support for the immunocompetence handicap hypothesis in the wild: hormonal manipulation decreases survival in sick damselflies.
abstract: The immunocompetence handicap hypothesis (ICHH) states that hormones enhance sexual trait expression but impair immunity. Previous tests of the ICHH have been hampered by experimental design problems. Here, we report on an experimental test of the ICHH that includes manipulations of both hormones and infections in males of the territorial damselfly, Hetaerina americana, with accurate survival measurements. We conducted a fully factorial experiment subjecting each individual to one of three topical treatments: methoprene (a juvenile hormone analog), acetone, or control, and one of three injection treatments: bacteria, PBS, or control. We measured survival of manipulated males in both the wild and in captivity. As predicted, survival was most heavily impaired in methoprene-bacteria males than in the other groups in the wild, and no survival differences emerged in captive animals. This result confirms that survival is one cost an animal pays for increased hormonal levels. This corroborates theoretical predictions of the ICHH.
authors.affiliation: Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, 04510, Mexico, DF, Mexico.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: González-Tokman
authors.forename: Roberto
authors.initials: R
authors.lastname: Munguía-Steyer
authors.forename: Isaac
authors.initials: I
authors.lastname: González-Santoyo
authors.forename: Fernanda S
authors.initials: FS
authors.lastname: Baena-Díaz
authors.forename: Alex
authors.initials: A
authors.lastname: Córdoba-Aguilar
mesh_terms: D000096:Acetone; D000818:Animals; D007121:Immunocompetence; D007605:Juvenile Hormones / Q000502:physiology*; D008297:Male; D008726:Methoprene; D009026:Mortality; D063191:Odonata / Q000276:immunology* / Q000382:microbiology; D012641:Selection, Genetic; D012706:Serratia marcescens; D012727:Sex Characteristics; D013731:Territoriality
chemical_list: D007605:Juvenile Hormones; D000096:Acetone; D008726:Methoprene