title: Interspecific associations between circulating antioxidant levels and life-history variation in birds.
abstract: Antioxidants play an important role in protecting tissues against aging-associated oxidative damage and are thus prime candidates for relating physiological mechanisms to variation in life histories. We measured total antioxidant capacity, antioxidant response to stress, and levels of uric acid, vitamin E, and four carotenoids in 95 avian species, mostly passerines from Michigan or Panama. We compared antioxidant measures to seven variables related to life histories (clutch size, survival rate, incubation period, nestling period, basal metabolic rate, body mass, and whether the species lived in a tropical or temperate climate). Life-history-related traits varied over at least three statistically independent axes. Higher antioxidant levels were generally characteristic of more rapid development, lower survival rate, smaller body size, larger clutch size, and higher mass-adjusted metabolic rate, but the relationships of particular antioxidants with individual life-history traits showed considerable complexity. Antioxidant-life history associations differed between tropical and temperate species and varied with respect to taxonomic sampling. Vitamin E showed few relationships with life-history traits. Overall, our results partly support the hypothesis that antioxidant levels evolve to mirror free radical production. Clearly, however, the complex patterns of physiological diversification observed here result from the interplay of many factors, likely including not just investment in somatic maintenance but also phylogenetic constraint, diet, and other aspects of ecology.
authors.affiliation: Department of Biology, University of Missouri, St Louis, Missouri 63121, USA. acohen@jhsph.edu
authors.forename: Alan A
authors.initials: AA
authors.lastname: Cohen
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: McGraw
authors.forename: Popko
authors.initials: P
authors.lastname: Wiersma
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Williams
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Robinson
authors.forename: Tara R
authors.initials: TR
authors.lastname: Robinson
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Brawn
authors.forename: Robert E
authors.initials: RE
authors.lastname: Ricklefs
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001481:Basal Metabolism; D001717:Birds / Q000033:anatomy & histology / Q000097:blood* / Q000254:growth & development; D049628:Body Size; D002338:Carotenoids / Q000097:blood; D052284:Clutch Size; D017753:Ecosystem; D008136:Longevity; D008824:Michigan; D009425:Nesting Behavior; D010176:Panama; D010802:Phylogeny; D025341:Principal Component Analysis; D013312:Stress, Physiological / Q000097:blood; D014329:Tropical Climate; D014527:Uric Acid / Q000097:blood; D014810:Vitamin E / Q000097:blood
chemical_list: D000975:Antioxidants; D014810:Vitamin E; D014527:Uric Acid; D002338:Carotenoids