Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl

Abstract The persistence of color polymorphism in nature may be driven by disassortative mating based on color. In vertebrates, body size sometimes correlates with coloration, complicating mating patterns, as the selective pressures favoring mixed-color pairs might be counterbalanced by those influe...

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Main Authors: Deseada Parejo, Erick González-Medina, Ángel Cruz-Miralles, Jesús Miguel Avilés
Format: Article
Language:English
Published: Nature Portfolio 2025-06-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-04191-1
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author Deseada Parejo
Erick González-Medina
Ángel Cruz-Miralles
Jesús Miguel Avilés
author_facet Deseada Parejo
Erick González-Medina
Ángel Cruz-Miralles
Jesús Miguel Avilés
author_sort Deseada Parejo
collection DOAJ
description Abstract The persistence of color polymorphism in nature may be driven by disassortative mating based on color. In vertebrates, body size sometimes correlates with coloration, complicating mating patterns, as the selective pressures favoring mixed-color pairs might be counterbalanced by those influencing body size. This complexity is heightened in species with reversed sexual size dimorphism, such as owls, where males are smaller than females, and average dissimilarity in mate size may reflect sexual size dimorphism rather than an active disassortative mating pattern. Here we investigate the fitness consequences of mating by color and body size using a long-term dataset from the color polymorphic Eurasian Scops owl (Otus scops), a bird species with reversed sexual size dimorphism. Results reveal that size-disassortative mating enhances reproductive success, as highly size-dimorphic pairs have higher probability of fledging owlets, which may favor reversed sexual size dimorphism. In addition, larger pairs produce heavier owlets with higher immunocompetence, aligning with the conventional size-based mating hypothesis. Although body size and plumage coloration were correlated within pairs, only differences in body size between pair members, not coloration, were related to higher fitness estimates. While color-based assortative mating had no direct impact on any of the fitness proxies studied, greyer pairs exhibited higher feeding rates to offspring than browner pairs. These results underscore the importance of simultaneously considering traits that may covary with color and shape mating patterns to understand the persistence of color polymorphisms in nature.
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spelling doaj-art-c34c171667774e148d60c3b6edda2fda2025-08-20T03:10:28ZengNature PortfolioScientific Reports2045-23222025-06-0115111310.1038/s41598-025-04191-1Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owlDeseada Parejo0Erick González-Medina1Ángel Cruz-Miralles2Jesús Miguel Avilés3Departamento de Ecología Funcional y Evolutiva, EEZA-CSICGrupo de Investigación en Conservación. Facultad de Ciencias., Universidad de ExtremaduraDepartamento de Ecología Funcional y Evolutiva, EEZA-CSICDepartamento de Ecología Funcional y Evolutiva, EEZA-CSICAbstract The persistence of color polymorphism in nature may be driven by disassortative mating based on color. In vertebrates, body size sometimes correlates with coloration, complicating mating patterns, as the selective pressures favoring mixed-color pairs might be counterbalanced by those influencing body size. This complexity is heightened in species with reversed sexual size dimorphism, such as owls, where males are smaller than females, and average dissimilarity in mate size may reflect sexual size dimorphism rather than an active disassortative mating pattern. Here we investigate the fitness consequences of mating by color and body size using a long-term dataset from the color polymorphic Eurasian Scops owl (Otus scops), a bird species with reversed sexual size dimorphism. Results reveal that size-disassortative mating enhances reproductive success, as highly size-dimorphic pairs have higher probability of fledging owlets, which may favor reversed sexual size dimorphism. In addition, larger pairs produce heavier owlets with higher immunocompetence, aligning with the conventional size-based mating hypothesis. Although body size and plumage coloration were correlated within pairs, only differences in body size between pair members, not coloration, were related to higher fitness estimates. While color-based assortative mating had no direct impact on any of the fitness proxies studied, greyer pairs exhibited higher feeding rates to offspring than browner pairs. These results underscore the importance of simultaneously considering traits that may covary with color and shape mating patterns to understand the persistence of color polymorphisms in nature.https://doi.org/10.1038/s41598-025-04191-1Body sizeColor polymorphismNon-random matingOwlsReversed sexual size dimorphism
spellingShingle Deseada Parejo
Erick González-Medina
Ángel Cruz-Miralles
Jesús Miguel Avilés
Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl
Scientific Reports
Body size
Color polymorphism
Non-random mating
Owls
Reversed sexual size dimorphism
title Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl
title_full Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl
title_fullStr Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl
title_full_unstemmed Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl
title_short Size, not color, drives assortative mating and influences fledging survival, weight and immunity in a polymorphic owl
title_sort size not color drives assortative mating and influences fledging survival weight and immunity in a polymorphic owl
topic Body size
Color polymorphism
Non-random mating
Owls
Reversed sexual size dimorphism
url https://doi.org/10.1038/s41598-025-04191-1
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