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Pap P.L.,Babes - Bolyai University | Pap P.L.,Debrecen University | Osvath G.,Babes - Bolyai University | Aparicio J.M.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | And 9 more authors.
PLoS ONE | Year: 2015

Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting. © 2015 Pap et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Munoz A.,Autonomous University of Barcelona | Munoz A.,University of Castilla - La Mancha | Aparicio J.M.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Bonal R.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Bonal R.,University of Castilla - La Mancha
Evolutionary Ecology | Year: 2011

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. © 2011 Springer Science+Business Media B.V.

Aparicio J.M.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Munoz A.,Complutense University of Madrid | Munoz A.,Autonomous University of Barcelona | Bonal R.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Moller A.P.,CNRS Ecology, Systematic and Evolution Laboratory
Biological Journal of the Linnean Society | Year: 2012

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.

Aparicio J.M.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Ortego J.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Ortego J.,CSIC - National Museum of Natural Sciences | Calabuig G.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural | Cordero P.J.,Grupo de Investigacion de la Biodiversidad Genetica y Cultural
Heredity | Year: 2010

Some alleles are inherited more frequently than expected from Mendel's rule. This phenomenon, known as transmission ratio distortion (TRD), is found in a broad variety of taxa, but it is thought to be unusual and occurs at a low frequency in any particular population. Here, we used seven microsatellite markers to search for possible TRD in a wild lesser kestrel (Falco naumanni) population. Among the nine alleles analysed with at least 200 known meioses for each sex, we found that two of them (156-AG5 in males and 362-FN1.11 in females) presented subtle (k=0.6) but significant departures from Mendelian segregation. Moreover, in a sample of 53 alleles with at least 15 known meioses, we found a positive correlation between their transmission rates and their frequencies in the population. To estimate the transmission scores for the loci and individuals, we developed a method that allowed us to discover that another locus, FP-46, showed significant TRD, despite the lack of a significant deviation from parity for the alleles considered individually. Finally, we found a consistent transmission bias both within loci and within individuals across loci. Inter-individual differences in TRD support the idea that distorters act over several loci that are evenly distributed across the whole genome, particularly in individuals bearing the distorter alleles. Overall, these findings suggest that TRD might be a more widespread phenomenon than previously revealed by analyses at the allele level. © 2010 Macmillan Publishers Limited. All rights reserved.

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