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Anders Pape Moller - One of the best experts on this subject based on the ideXlab platform.
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Population differences in density and resource allocation of ornamental Tail Feathers in the barn swallow
Biological Journal of the Linnean Society, 2012Co-Authors: José Miguel Aparicio, Alberto Muñoz, Raúl Bonal, Anders Pape MollerAbstract:Many organisms show well-defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost Tail Feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of Tail Feathers in relation to body size and wing size. Tail Feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer Tails. The extra enlargement of the Tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying Feather structure to produce longer Feathers of lower density. These two separate processes accounting for the production of longer and more costly Tail Feathers and less dense Feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long Tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 925–936.
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The allometric pattern of sexually size dimorphic Feather ornaments and factors affecting allometry
Journal of Evolutionary Biology, 2009Co-Authors: José Javier Cuervo, Anders Pape MollerAbstract:The static allometry of secondary sexual characters is currently subject to debate. While some studies suggest an almost universal positive allometry for such traits, but isometry or negative allometry for nonornamental traits, other studies maintain that any kind of allometric pattern is possible. Therefore, we investigated the allometry of sexually size dimorphic Feather ornaments in 67 species of birds. We also studied the allometry of female Feathers homologous to male ornaments (female ornaments in the following) and ordinary nonsexual traits. Allometries were estimated as reduced major axis slopes of trait length on tarsus length. Ornamental Feathers showed positive allometric slopes in both sexes, although that was not a peculiarity for ornamental Feathers, because nonsexual Tail Feathers also showed positive allometry. Migration distance (in males) and relative size of the Tail ornament (in females) tended to be negatively related to the allometric slope of Tail Feather ornaments, although these results were not conclusive. Finally, we found an association between mating system and allometry of Tail Feather ornaments, with species with more intense sexual selection showing a smaller degree of allometry of Tail ornaments. This study is consistent with theoretical models that predict no specific kind of allometric pattern for sexual and nonsexual characters.
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sexual selection Feather breakage and parasites the importance of white spots in the Tail of the barn swallow hirundo rustica
Behavioral Ecology and Sociobiology, 1999Co-Authors: Mati Kose, Anders Pape MollerAbstract:The long outermost Tail Feathers of barn swallows Hirundo rustica have white spots that are larger in males than in females and in adults than in juveniles. Spot size increases with age among adults and is positively correlated with Tail length. We tested the functional significance of these white spots by randomly assigning males to either of three groups during spring: (1) subjected to a considerable reduction in the size of all spots using a black permanent pen; (2) subjected to a small reduction in the size of all spots; or (3) a control group with no reduction. Experimental treatment significantly affected the total number of offspring produced per season: breeding tended to be delayed and second broods were less frequent after a considerable reduction in the size of the males' Tail Feather spots. White parts of Feathers lacking melanin were more often found to be the site of Feather breakage than the melanised parts of similar width. Furthermore, white Tail spots were the preferred feeding site of Feather-eating Mallophaga and, since long-Tailed males have fewer Mallophaga than short-Tailed males, long-Tailed males may pay a lower cost for their large white Tail spots than short-Tailed males. Hence, the cost of increased risk of Feather breakage at white Tail spots and the non-random distribution of Feather lice among individuals will render Tail spots a reliable signal of phenotypic quality.
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sexual selection Feather breakage and parasites the importance of white spots in the Tail of the barn swallow hirundo rustica
Behavioral Ecology and Sociobiology, 1999Co-Authors: Mati Kose, Anders Pape MollerAbstract:The long outermost Tail Feathers of barn swallows Hirundo rustica have white spots that are larger in males than in females and in adults than in juveniles. Spot size increases with age among adults and is positively correlated with Tail length. We tested the functional significance of these white spots by randomly assigning males to either of three groups during spring: (1) subjected to a considerable reduction in the size of all spots using a black permanent pen; (2) subjected to a small reduction in the size of all spots; or (3) a control group with no reduction. Experimental treatment significantly affected the total number of offspring produced per season: breeding tended to be delayed and second broods were less frequent after a considerable reduction in the size of the males' Tail Feather spots. White parts of Feathers lacking melanin were more often found to be the site of Feather breakage than the melanised parts of similar width. Furthermore, white Tail spots were the preferred feeding site of Feather-eating Mallophaga and, since long-Tailed males have fewer Mallophaga than short-Tailed males, long-Tailed males may pay a lower cost for their large white Tail spots than short-Tailed males. Hence, the cost of increased risk of Feather breakage at white Tail spots and the non-random distribution of Feather lice among individuals will render Tail spots a reliable signal of phenotypic quality.
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Repeatability of female choice in a monogamous swallow
Animal Behaviour, 1994Co-Authors: Anders Pape MollerAbstract:Abstract Abstract. Models of the evolution of female mate preferences often assume that there is a genetic basis for female choosiness, although there are few empirical tests of this assumption. One way in which to estimate consistency in female mate preferences is to calculate the repeatability of characters of males chosen by females on different mate choice occasions. Repeatability of female mate choice for morphological characters of males chosen in different years was estimated in the monogamous barn swallow, Hirundo rustica . There was no significant repeatability of mate preferences for the absolute size of male traits. However, females have different numbers of males and phenotype ranges available at different mate choice events. The rank of chosen male phenotypes demonstrated significant repeatability for the length of the outermost Tail Feather, but not for wing length, the length of the short central Tail Feather, or tarsus length. Consistency in female mate preferences could be due to genetic or environmental factors.
Raúl Bonal - One of the best experts on this subject based on the ideXlab platform.
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Population differences in density and resource allocation of ornamental Tail Feathers in the barn swallow
Biological Journal of the Linnean Society, 2012Co-Authors: José Miguel Aparicio, Alberto Muñoz, Raúl Bonal, Anders Pape MollerAbstract:Many organisms show well-defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost Tail Feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of Tail Feathers in relation to body size and wing size. Tail Feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer Tails. The extra enlargement of the Tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying Feather structure to produce longer Feathers of lower density. These two separate processes accounting for the production of longer and more costly Tail Feathers and less dense Feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long Tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 925–936.
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Male barn swallows use different signalling rules to produce ornamental Tail Feathers
Evolutionary Ecology, 2011Co-Authors: Alberto Muñoz, José Miguel Aparicio, Raúl BonalAbstract:The evolution of secondary sexual characters is the subject of controversial debate between those defending their role as ‘viability indicators’ and those arguing that ornaments are purely ‘attractive traits’ selected by females. Recent theoretical studies suggest that these hypotheses are not mutually exclusive, as both viability and attractiveness can contribute to improve the reproductive success of progeny and could thus simultaneously underlie female choices. If that is the case, strategies of cheaper advertisement, allowing the expression of larger ornaments for the same cost, could proliferate even in species in which honest signalling of viability prevails. Under this scenario, different males could invest a different amount of resources per ornament unit of expression, thus using different signalling rules. We studied the relationship between Tail Feather length (a trait that is the subject of a female mate preference) and Feather mass (a measure of investment in Feather production) in a barn swallow Hirundo rustica population. Different males used different and consistent signalling rules when developing ornamental Feathers. That is, to produce a Feather of a given length, each male used a constant amount of resources across different years, but this amount varied between males. Although the amount of material invested in Feathers (Feather mass) is a condition-dependent trait, the organization of this material in ornamental Feathers (i.e. the signalling rules) was not. Neither survival nor risk of Feather breakage was related to the signalling rules. Thus, these results suggest that both ‘viability’ and ‘runaway’ mechanisms are independent determinants of the evolution of ornamental sexual Feathers in the barn swallow. A preference for long Tails will ensure that females either obtain a sire with high viability, or one transferring the capability to produce longer and more attractive Tails at a lower cost of production to its offspring.
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Male barn swallows use different resource allocation rules to produce ornamental Tail Feathers
Behavioral Ecology, 2008Co-Authors: Alberto Muñoz, José Miguel Aparicio, Raúl BonalAbstract:Sexual ornaments compete for resources with other functional traits. Such resource allocation trade-offs should ensure the honesty of sexual ornaments according to the Zahavi's handicap principle. However, the existence of costly signals could not be enough to guarantee honesty if different individuals invest different proportions of their limited resources in ornaments. Then, a certain level of sexual signaling would correspond to several levels of individual condition. Here, we explore whether there are different resource allocation rules in Tail Feather ornaments between males within a barn swallow (Hirundo rustica) population and whether these different rules confer different viability to males. We assessed the proportion of resources invested in ornamental Feathers compared with other functional Feathers moulted and growing during the same period at expenses of the same resources. We found that 1) different males allocate a different proportion of resources to ornamental Feathers in relation to functional Feathers and this proportion is repeatable between years and 2) male survival likelihood decreased as the proportion of resources allocated to ornamental Feathers increased. Survival costs associated with increased investments in ornaments can maintain the sexual signaling system honest at population level but do not preclude the existence of an array of different allocation rules between males. Thus, males with different viability can produce ornamental Feathers of the same length. These results show that the relationship between male viability and ornament expression can be less straightforward than considered previously. Copyright 2008, Oxford University Press.
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Evolution of the structure of Tail Feathers: implications for the theory of sexual selection.
Evolution; international journal of organic evolution, 2003Co-Authors: José Miguel Aparicio, Raúl Bonal, Pedro J. CorderoAbstract:Bird Tails are extraordinarily variable in length and functionality. In some species, males have evolved exaggeratedly long Tails as a result of sexual selection. Changes in Tail length should be associated with changes in Feather structure. The study of the evolution of Feather structure in bird Tails could give insight to understand the causes and means of evolution in relation to processes of sexual selection. In theory, three possible means of Tail length evolution in relation to structural components might be expected: (1) a positive relationship between the increase in length and size of structural components maintaining the mechanical properties of the Feather; (2) no relationship; that is, enlarging Feather length without changes in the structural components; and (3) a negative relationship; that is, enlarging Feather length by reducing structural components. These hypotheses were tested using phylogenetic analyses to examine changes in both degree of exaggeration in Tail length and structural characteristics of Tail Feathers (rachis width and density of barbs) in 36 species, including those dimorphic and nondimorphic in Tail length. The degree of sexual dimorphism in Tail length was negatively correlated with both rachis width and density of barbs in males but not in females. Reinforcing this result, we found that dimorphism in Tail length was negatively associated with dimorphism in Tail Feather structure (rachis width and density of barbs). These results support the third hypothesis, in which the evolution of long Feathers occurs at the expense of making them simpler and therefore less costly to produce. However, we do not know the effects of enfeeblement on the costs of bearing. If the total costs increased, the enfeeblement of Feathers could be explained as a reinforcement of the honesty of the signal. Alternatively, if total costs were reduced, the strategy could be explained by cheating processes. The study of female preferences for fragile Tail Feathers is essential to test these two hypotheses. Preferences for fragile Tails would support the evolution of reinforcement of honesty, whereas female indifference would indicate the existence of cheating in certain stages of the evolutionary process.
José Miguel Aparicio - One of the best experts on this subject based on the ideXlab platform.
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Population differences in density and resource allocation of ornamental Tail Feathers in the barn swallow
Biological Journal of the Linnean Society, 2012Co-Authors: José Miguel Aparicio, Alberto Muñoz, Raúl Bonal, Anders Pape MollerAbstract:Many organisms show well-defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost Tail Feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of Tail Feathers in relation to body size and wing size. Tail Feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer Tails. The extra enlargement of the Tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying Feather structure to produce longer Feathers of lower density. These two separate processes accounting for the production of longer and more costly Tail Feathers and less dense Feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long Tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 925–936.
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Male barn swallows use different signalling rules to produce ornamental Tail Feathers
Evolutionary Ecology, 2011Co-Authors: Alberto Muñoz, José Miguel Aparicio, Raúl BonalAbstract:The evolution of secondary sexual characters is the subject of controversial debate between those defending their role as ‘viability indicators’ and those arguing that ornaments are purely ‘attractive traits’ selected by females. Recent theoretical studies suggest that these hypotheses are not mutually exclusive, as both viability and attractiveness can contribute to improve the reproductive success of progeny and could thus simultaneously underlie female choices. If that is the case, strategies of cheaper advertisement, allowing the expression of larger ornaments for the same cost, could proliferate even in species in which honest signalling of viability prevails. Under this scenario, different males could invest a different amount of resources per ornament unit of expression, thus using different signalling rules. We studied the relationship between Tail Feather length (a trait that is the subject of a female mate preference) and Feather mass (a measure of investment in Feather production) in a barn swallow Hirundo rustica population. Different males used different and consistent signalling rules when developing ornamental Feathers. That is, to produce a Feather of a given length, each male used a constant amount of resources across different years, but this amount varied between males. Although the amount of material invested in Feathers (Feather mass) is a condition-dependent trait, the organization of this material in ornamental Feathers (i.e. the signalling rules) was not. Neither survival nor risk of Feather breakage was related to the signalling rules. Thus, these results suggest that both ‘viability’ and ‘runaway’ mechanisms are independent determinants of the evolution of ornamental sexual Feathers in the barn swallow. A preference for long Tails will ensure that females either obtain a sire with high viability, or one transferring the capability to produce longer and more attractive Tails at a lower cost of production to its offspring.
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Male barn swallows use different resource allocation rules to produce ornamental Tail Feathers
Behavioral Ecology, 2008Co-Authors: Alberto Muñoz, José Miguel Aparicio, Raúl BonalAbstract:Sexual ornaments compete for resources with other functional traits. Such resource allocation trade-offs should ensure the honesty of sexual ornaments according to the Zahavi's handicap principle. However, the existence of costly signals could not be enough to guarantee honesty if different individuals invest different proportions of their limited resources in ornaments. Then, a certain level of sexual signaling would correspond to several levels of individual condition. Here, we explore whether there are different resource allocation rules in Tail Feather ornaments between males within a barn swallow (Hirundo rustica) population and whether these different rules confer different viability to males. We assessed the proportion of resources invested in ornamental Feathers compared with other functional Feathers moulted and growing during the same period at expenses of the same resources. We found that 1) different males allocate a different proportion of resources to ornamental Feathers in relation to functional Feathers and this proportion is repeatable between years and 2) male survival likelihood decreased as the proportion of resources allocated to ornamental Feathers increased. Survival costs associated with increased investments in ornaments can maintain the sexual signaling system honest at population level but do not preclude the existence of an array of different allocation rules between males. Thus, males with different viability can produce ornamental Feathers of the same length. These results show that the relationship between male viability and ornament expression can be less straightforward than considered previously. Copyright 2008, Oxford University Press.
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Evolution of the structure of Tail Feathers: implications for the theory of sexual selection.
Evolution; international journal of organic evolution, 2003Co-Authors: José Miguel Aparicio, Raúl Bonal, Pedro J. CorderoAbstract:Bird Tails are extraordinarily variable in length and functionality. In some species, males have evolved exaggeratedly long Tails as a result of sexual selection. Changes in Tail length should be associated with changes in Feather structure. The study of the evolution of Feather structure in bird Tails could give insight to understand the causes and means of evolution in relation to processes of sexual selection. In theory, three possible means of Tail length evolution in relation to structural components might be expected: (1) a positive relationship between the increase in length and size of structural components maintaining the mechanical properties of the Feather; (2) no relationship; that is, enlarging Feather length without changes in the structural components; and (3) a negative relationship; that is, enlarging Feather length by reducing structural components. These hypotheses were tested using phylogenetic analyses to examine changes in both degree of exaggeration in Tail length and structural characteristics of Tail Feathers (rachis width and density of barbs) in 36 species, including those dimorphic and nondimorphic in Tail length. The degree of sexual dimorphism in Tail length was negatively correlated with both rachis width and density of barbs in males but not in females. Reinforcing this result, we found that dimorphism in Tail length was negatively associated with dimorphism in Tail Feather structure (rachis width and density of barbs). These results support the third hypothesis, in which the evolution of long Feathers occurs at the expense of making them simpler and therefore less costly to produce. However, we do not know the effects of enfeeblement on the costs of bearing. If the total costs increased, the enfeeblement of Feathers could be explained as a reinforcement of the honesty of the signal. Alternatively, if total costs were reduced, the strategy could be explained by cheating processes. The study of female preferences for fragile Tail Feathers is essential to test these two hypotheses. Preferences for fragile Tails would support the evolution of reinforcement of honesty, whereas female indifference would indicate the existence of cheating in certain stages of the evolutionary process.
Hailin Cong - One of the best experts on this subject based on the ideXlab platform.
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Thin Film Interference of Colloidal Thin Films
Langmuir, 2004Co-Authors: Hailin CongAbstract:A stairlike colloidal crystal thin film composed of poly(styrene−methyl methacrylate−acrylic acid) (P(St-MMA-AA)) monodispersed colloids was fabricated on an inclined silicon substrate. Different bright colors were observed on the various parts of the film with different layers as white light irradiated perpendicularly on it. The relationship between the colors and layers of the film was investigated and discussed according to the principle of thin film interference. On the basis of the phenomenon of thin film interference, a one-layer colloidal film having uniform color was researched and it would display diverse colors before and after swollen by styrene (St). A circular stairlike colloidal film was achieved to mimic the colors of the peacock Tail Feather.
Alberto Muñoz - One of the best experts on this subject based on the ideXlab platform.
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Population differences in density and resource allocation of ornamental Tail Feathers in the barn swallow
Biological Journal of the Linnean Society, 2012Co-Authors: José Miguel Aparicio, Alberto Muñoz, Raúl Bonal, Anders Pape MollerAbstract:Many organisms show well-defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost Tail Feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of Tail Feathers in relation to body size and wing size. Tail Feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer Tails. The extra enlargement of the Tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying Feather structure to produce longer Feathers of lower density. These two separate processes accounting for the production of longer and more costly Tail Feathers and less dense Feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long Tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 925–936.
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Male barn swallows use different signalling rules to produce ornamental Tail Feathers
Evolutionary Ecology, 2011Co-Authors: Alberto Muñoz, José Miguel Aparicio, Raúl BonalAbstract:The evolution of secondary sexual characters is the subject of controversial debate between those defending their role as ‘viability indicators’ and those arguing that ornaments are purely ‘attractive traits’ selected by females. Recent theoretical studies suggest that these hypotheses are not mutually exclusive, as both viability and attractiveness can contribute to improve the reproductive success of progeny and could thus simultaneously underlie female choices. If that is the case, strategies of cheaper advertisement, allowing the expression of larger ornaments for the same cost, could proliferate even in species in which honest signalling of viability prevails. Under this scenario, different males could invest a different amount of resources per ornament unit of expression, thus using different signalling rules. We studied the relationship between Tail Feather length (a trait that is the subject of a female mate preference) and Feather mass (a measure of investment in Feather production) in a barn swallow Hirundo rustica population. Different males used different and consistent signalling rules when developing ornamental Feathers. That is, to produce a Feather of a given length, each male used a constant amount of resources across different years, but this amount varied between males. Although the amount of material invested in Feathers (Feather mass) is a condition-dependent trait, the organization of this material in ornamental Feathers (i.e. the signalling rules) was not. Neither survival nor risk of Feather breakage was related to the signalling rules. Thus, these results suggest that both ‘viability’ and ‘runaway’ mechanisms are independent determinants of the evolution of ornamental sexual Feathers in the barn swallow. A preference for long Tails will ensure that females either obtain a sire with high viability, or one transferring the capability to produce longer and more attractive Tails at a lower cost of production to its offspring.
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Male barn swallows use different resource allocation rules to produce ornamental Tail Feathers
Behavioral Ecology, 2008Co-Authors: Alberto Muñoz, José Miguel Aparicio, Raúl BonalAbstract:Sexual ornaments compete for resources with other functional traits. Such resource allocation trade-offs should ensure the honesty of sexual ornaments according to the Zahavi's handicap principle. However, the existence of costly signals could not be enough to guarantee honesty if different individuals invest different proportions of their limited resources in ornaments. Then, a certain level of sexual signaling would correspond to several levels of individual condition. Here, we explore whether there are different resource allocation rules in Tail Feather ornaments between males within a barn swallow (Hirundo rustica) population and whether these different rules confer different viability to males. We assessed the proportion of resources invested in ornamental Feathers compared with other functional Feathers moulted and growing during the same period at expenses of the same resources. We found that 1) different males allocate a different proportion of resources to ornamental Feathers in relation to functional Feathers and this proportion is repeatable between years and 2) male survival likelihood decreased as the proportion of resources allocated to ornamental Feathers increased. Survival costs associated with increased investments in ornaments can maintain the sexual signaling system honest at population level but do not preclude the existence of an array of different allocation rules between males. Thus, males with different viability can produce ornamental Feathers of the same length. These results show that the relationship between male viability and ornament expression can be less straightforward than considered previously. Copyright 2008, Oxford University Press.
