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Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird

Postcopulatory sexual selection is an important force in the evolution of reproductive traits, including sperm morphology. In birds, sperm morphology is known to be highly heritable and largely condition-independent. Theory predicts, and recent comparative work corroborates, that strong selection in...

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Autores principales: Calhim, Sara, Double, Michael C., Margraf, Nicolas, Birkhead, Tim R., Cockburn, Andrew
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2011
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3240631/
https://www.ncbi.nlm.nih.gov/pubmed/22194918
http://dx.doi.org/10.1371/journal.pone.0028809
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author Calhim, Sara
Double, Michael C.
Margraf, Nicolas
Birkhead, Tim R.
Cockburn, Andrew
author_facet Calhim, Sara
Double, Michael C.
Margraf, Nicolas
Birkhead, Tim R.
Cockburn, Andrew
author_sort Calhim, Sara
collection PubMed
description Postcopulatory sexual selection is an important force in the evolution of reproductive traits, including sperm morphology. In birds, sperm morphology is known to be highly heritable and largely condition-independent. Theory predicts, and recent comparative work corroborates, that strong selection in such traits reduces intraspecific phenotypic variation. Here we show that some variation can be maintained despite extreme promiscuity, as a result of opposing, copulation-role-specific selection forces. After controlling for known correlates of siring success in the superb fairy-wren (Malurus cyaneus), we found that (a) lifetime extra-pair paternity success was associated with sperm with a shorter flagellum and relatively large head, and (b) males whose sperm had a longer flagellum and a relatively smaller head achieved higher within-pair paternity. In this species extrapair copulations occur in the same morning, but preceding, pair copulations during a female's fertile period, suggesting that shorter and relatively larger-headed sperm are most successful in securing storage (defense), whereas the opposite phenotype might be better at outcompeting stored sperm (offense). Furthermore, since cuckolding ability is a major contributor to differential male reproductive output, stronger selection on defense sperm competition traits might explain the short sperm of malurids relative to other promiscuous passerines.
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spelling pubmed-32406312011-12-22 Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird Calhim, Sara Double, Michael C. Margraf, Nicolas Birkhead, Tim R. Cockburn, Andrew PLoS One Research Article Postcopulatory sexual selection is an important force in the evolution of reproductive traits, including sperm morphology. In birds, sperm morphology is known to be highly heritable and largely condition-independent. Theory predicts, and recent comparative work corroborates, that strong selection in such traits reduces intraspecific phenotypic variation. Here we show that some variation can be maintained despite extreme promiscuity, as a result of opposing, copulation-role-specific selection forces. After controlling for known correlates of siring success in the superb fairy-wren (Malurus cyaneus), we found that (a) lifetime extra-pair paternity success was associated with sperm with a shorter flagellum and relatively large head, and (b) males whose sperm had a longer flagellum and a relatively smaller head achieved higher within-pair paternity. In this species extrapair copulations occur in the same morning, but preceding, pair copulations during a female's fertile period, suggesting that shorter and relatively larger-headed sperm are most successful in securing storage (defense), whereas the opposite phenotype might be better at outcompeting stored sperm (offense). Furthermore, since cuckolding ability is a major contributor to differential male reproductive output, stronger selection on defense sperm competition traits might explain the short sperm of malurids relative to other promiscuous passerines. Public Library of Science 2011-12-15 /pmc/articles/PMC3240631/ /pubmed/22194918 http://dx.doi.org/10.1371/journal.pone.0028809 Text en Calhim et al. http://creativecommons.org/licenses/by/4.0/ 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 properly credited.
spellingShingle Research Article
Calhim, Sara
Double, Michael C.
Margraf, Nicolas
Birkhead, Tim R.
Cockburn, Andrew
Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
title Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
title_full Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
title_fullStr Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
title_full_unstemmed Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
title_short Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
title_sort maintenance of sperm variation in a highly promiscuous wild bird
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3240631/
https://www.ncbi.nlm.nih.gov/pubmed/22194918
http://dx.doi.org/10.1371/journal.pone.0028809
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