The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Anders Pape Moller - One of the best experts on this subject based on the ideXlab platform.
-
gape coloration reliably reflects Immunocompetence of barn swallow hirundo rustica nestlings
Behavioral Ecology, 2003Co-Authors: Nicola Saino, Roberta Martinelli, Roberto Ambrosini, Paola Di Ninni, Anders Pape MollerAbstract:In some passerines, parents allocate more food to offspring with the brightest red gapes, but the function of parental decisions based on offspring gape coloration is unknown. We hypothesize that gape coloration is part of a communication system where nestlings reveal their condition to attending parents, which may thus base their decisions on reliable signals of offspring reproductive value. We analyze the effects of brood size manipulation, injection with an immunogen and food deprivation, on gape coloration, morphology, and T-cell--mediated Immunocompetence of nestling barn swallows (Hirundo rustica). For each gape we measured three components of coloration (hue, saturation, and brightness) and obtained an overall color score by principal component analysis. Enlargement of brood size and injection with an antigen resulted in less red and less saturated and brighter gape color. Nestlings in enlarged broods had smaller body mass and T-cell--mediated Immunocompetence compared to those in reduced broods. A positive covariation existed between redness and saturation of gape color and T-cell--mediated Immunocompetence. Gape color siblings raised in different nests did not depend on parentage. Thus, condition-dependent gape coloration can reveal different components of nestling state on which parents may base their adaptive decisions about allocation of care to the offspring. Copyright 2003.
-
does clutch size evolve in response to parasites and Immunocompetence
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Thomas E Martin, Anders Pape Moller, Santiago Merino, Jean ClobertAbstract:Parasites have been argued to influence clutch size evolution, but past work and theory has largely focused on within-species optimization solutions rather than clearly addressing among-species variation. The effects of parasites on clutch size variation among species can be complex, however, because different parasites can induce age-specific differences in mortality that can cause clutch size to evolve in different directions. We provide a conceptual argument that differences in Immunocompetence among species should integrate differences in overall levels of parasite-induced mortality to which a species is exposed. We test this assumption and show that mortality caused by parasites is positively correlated with Immunocompetence measured by cell-mediated measures. Under life history theory, clutch size should increase with increased adult mortality and decrease with increased juvenile mortality. Using Immunocompetence as a general assay of parasite-induced mortality, we tested these predictions by using data for 25 species. We found that clutch size increased strongly with adult Immunocompetence. In contrast, clutch size decreased weakly with increased juvenile Immunocompetence. But, Immunocompetence of juveniles may be constrained by selection on adults, and, when we controlled for adult Immunocompetence, clutch size decreased with juvenile Immunocompetence. Thus, Immunocompetence seems to reflect evolutionary differences in parasite virulence experienced by species, and differences in age-specific parasite virulence appears to exert opposite selection on clutch size evolution.
-
Immunocompetence ornamentation and viability of male barn swallows hirundo rustica
Proceedings of the National Academy of Sciences of the United States of America, 1997Co-Authors: Nicola Saino, Anna Maria Bolzern, Anders Pape MollerAbstract:Immunocompetence (i.e., the ability to produce an immune response to pathogens) can be predicted to influence the chances that organisms have to survive and reproduce. In this study we simulated a challenge to the immune systems of male barn swallows (Hirundo rustica) by injecting them intraperitoneally with a multigenic antigen, sheep red blood cells, and we analyzed long-term survival in relation to their Immunocompetence. Males were assigned to four groups that differed for the treatment of the length of the outermost tail feathers, a sexually dimorphic ornamental character that is currently under directional sexual selection. Immunocompetence was measured as change of concentration of gamma globulins relative to plasma proteins. The intensity of the immune response was independent of age. Males that showed the highest short-term response to sheep red blood cells were more likely to survive until the breeding season following that in which they had been inoculated, a pattern consistently observed within each experimental group. Males with comparatively long tails were more likely to survive than those with short tails. To our knowledge, the results of this study are the first to demonstrate that Immunocompetence can predict long-term survival in a free-ranging vertebrate. Moreover, they are compatible with current models of parasite-mediated sexual selection because long-tailed males are more immunocompetent than short-tailed ones, and females, by preferring to mate with the most ornamented males, may acquire the “good genes” for high Immunocompetence and, hence, for high viability of their offspring.
Nicola Saino - One of the best experts on this subject based on the ideXlab platform.
-
gape coloration reliably reflects Immunocompetence of barn swallow hirundo rustica nestlings
Behavioral Ecology, 2003Co-Authors: Nicola Saino, Roberta Martinelli, Roberto Ambrosini, Paola Di Ninni, Anders Pape MollerAbstract:In some passerines, parents allocate more food to offspring with the brightest red gapes, but the function of parental decisions based on offspring gape coloration is unknown. We hypothesize that gape coloration is part of a communication system where nestlings reveal their condition to attending parents, which may thus base their decisions on reliable signals of offspring reproductive value. We analyze the effects of brood size manipulation, injection with an immunogen and food deprivation, on gape coloration, morphology, and T-cell--mediated Immunocompetence of nestling barn swallows (Hirundo rustica). For each gape we measured three components of coloration (hue, saturation, and brightness) and obtained an overall color score by principal component analysis. Enlargement of brood size and injection with an antigen resulted in less red and less saturated and brighter gape color. Nestlings in enlarged broods had smaller body mass and T-cell--mediated Immunocompetence compared to those in reduced broods. A positive covariation existed between redness and saturation of gape color and T-cell--mediated Immunocompetence. Gape color siblings raised in different nests did not depend on parentage. Thus, condition-dependent gape coloration can reveal different components of nestling state on which parents may base their adaptive decisions about allocation of care to the offspring. Copyright 2003.
-
Immunocompetence ornamentation and viability of male barn swallows hirundo rustica
Proceedings of the National Academy of Sciences of the United States of America, 1997Co-Authors: Nicola Saino, Anna Maria Bolzern, Anders Pape MollerAbstract:Immunocompetence (i.e., the ability to produce an immune response to pathogens) can be predicted to influence the chances that organisms have to survive and reproduce. In this study we simulated a challenge to the immune systems of male barn swallows (Hirundo rustica) by injecting them intraperitoneally with a multigenic antigen, sheep red blood cells, and we analyzed long-term survival in relation to their Immunocompetence. Males were assigned to four groups that differed for the treatment of the length of the outermost tail feathers, a sexually dimorphic ornamental character that is currently under directional sexual selection. Immunocompetence was measured as change of concentration of gamma globulins relative to plasma proteins. The intensity of the immune response was independent of age. Males that showed the highest short-term response to sheep red blood cells were more likely to survive until the breeding season following that in which they had been inoculated, a pattern consistently observed within each experimental group. Males with comparatively long tails were more likely to survive than those with short tails. To our knowledge, the results of this study are the first to demonstrate that Immunocompetence can predict long-term survival in a free-ranging vertebrate. Moreover, they are compatible with current models of parasite-mediated sexual selection because long-tailed males are more immunocompetent than short-tailed ones, and females, by preferring to mate with the most ornamented males, may acquire the “good genes” for high Immunocompetence and, hence, for high viability of their offspring.
H K Parmentier - One of the best experts on this subject based on the ideXlab platform.
-
A tradeoff between Immunocompetence and sexual ornamentation in domestic fowl (Immunocompetence handicap hypothesisysheep erythrocyteysexual ornamentsyGallus domesticusytestosterone)
1999Co-Authors: Simon Verhulst, H K ParmentierAbstract:Females often select their mates on the basis of the size or intensity of sexual ornaments, and it is thought that such traits are reliable indicators of male quality because the costliness of these traits prevents cheating. The immuno- competence handicap hypothesis is a recently proposed mech- anistic explanation of these costs and states that males carry ornaments at the expense of their resistance to disease and parasites. The tradeoff between Immunocompetence and sex- ual ornamentation was hypothesized to arise as a consequence of the dual effect of androgens on ornamentation (1) and immune function (2). To test this hypothesis, we compared comb size between male domestic chickens Gallus domesticus of lines divergently selected for antibody responses to sheep erythrocytes (three lines: selected for low response or high response and a control line). The importance of comb size in inter- and intrasexual selection is well established, and comb size is strongly dependent on testosterone level. Comb size was larger in the males of the low line than in the high line, and comb size of control males was intermediate, indicating a tradeoff between ornamentation and Immunocompetence. Testosterone (T) levels varied in a similar fashion (TLow > TControl >T High), suggesting that this hormone could mediate the tradeoff between ornamentation and Immunocompetence. These results support the idea that a tradeoff with immune function may constrain the expression of secondary sexual ornaments.
-
a tradeoff between Immunocompetence and sexual ornamentation in domestic fowl
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Simon Verhulst, S J Dieleman, H K ParmentierAbstract:Females often select their mates on the basis of the size or intensity of sexual ornaments, and it is thought that such traits are reliable indicators of male quality because the costliness of these traits prevents cheating. The Immunocompetence handicap hypothesis is a recently proposed mechanistic explanation of these costs and states that males carry ornaments at the expense of their resistance to disease and parasites. The tradeoff between Immunocompetence and sexual ornamentation was hypothesized to arise as a consequence of the dual effect of androgens on ornamentation (+) and immune function (−). To test this hypothesis, we compared comb size between male domestic chickens Gallus domesticus of lines divergently selected for antibody responses to sheep erythrocytes (three lines: selected for low response or high response and a control line). The importance of comb size in inter- and intrasexual selection is well established, and comb size is strongly dependent on testosterone level. Comb size was larger in the males of the low line than in the high line, and comb size of control males was intermediate, indicating a tradeoff between ornamentation and Immunocompetence. Testosterone (T) levels varied in a similar fashion (TLow > TControl > THigh), suggesting that this hormone could mediate the tradeoff between ornamentation and Immunocompetence. These results support the idea that a tradeoff with immune function may constrain the expression of secondary sexual ornaments.
M.r. Evans - One of the best experts on this subject based on the ideXlab platform.
-
Ectoparasites of house sparrows (Passer domesticus): An experimental test of the Immunocompetence handicap hypothesis and a new model
Behavioral Ecology and Sociobiology, 2000Co-Authors: A. Poiani, A R Goldsmith, M.r. EvansAbstract:Conspicuous secondary sexual traits may have evolved as handicap-revealing signals or as badges of status. We present results of an experiment using males of the sexually dimorphic house sparrow (Passer domesticus), that support the idea that the male-specific bib can be both a handicap-revealing signal and a reliable badge indicating the physical condition of the bird. In a test of the Immunocompetence handicap hypothesis, wild-caught adult male house sparrows were studied in captivity. Birds implanted with elevated doses of testosterone were more dominant, had higher circulating levels of both testosterone and corticosterone and they also harboured relatively larger ectoparasite loads. Higher parasite loads were also associated with individuals showing lower Immunocompetence and larger changes in bib size. A new model for Immunocompetence effects in sexual selection is introduced, integrating actions that the hypothalamopituitary axis exerts on gonads, adrenals and the thyroid gland. The ”integrated Immunocompetence model” synthesizes both the ”handicap” (i.e. survival-decreasing) and ”badge of status” (i.e. survival- enhancing) models for evolution of secondary sexual traits.
Florentino De Lope - One of the best experts on this subject based on the ideXlab platform.
-
seasonal variation in the relationship between cellular immune response and badge size in male house sparrows passer domesticus
Behavioral Ecology and Sociobiology, 1999Co-Authors: Guillermo Gonzalez, Gabriele Sorci, Florentino De LopeAbstract:The Immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signals of male quality because steroid hormones (such as corticosteroids and sex steroids), which are supposed to favor the development of secondary sexual traits, may also have immunosuppressive effects. Certain secondary sexual traits are not only used as mate choice signals but also play a role as badges of status. In the house sparrow (Passer domesticus), males have a bib of black feathers which is used both as a signal of social status in male-male interactions and by females when choosing a mate. We investigated the relationships between bib size and cellular immune response in male house sparrows during and outside the reproductive season. Males with large badges were found to have lower levels of Immunocompetence, as assessed using a T-cell-mediated immunity assay, during the reproductive season, as predicted by the Immunocompetence handicap hypothesis. Conversely, in November, the correlation between badge size and cellular immune response was positive, possibly reflecting the better access to trophic resources of large-badged dominant males in winter flocks.
