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When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility?
ABSTRACT: In birds with extrapair mating, older males usually have higher fertilization success than younger males. Two hypotheses can potentially explain this pattern: 1) females prefer older, and often more ornamented males, or 2) older males invest more in reproduction and fertility than younger...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Springer Berlin Heidelberg
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9034975/ https://www.ncbi.nlm.nih.gov/pubmed/35535127 http://dx.doi.org/10.1007/s00265-022-03170-0 |
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author | Lifjeld, Jan T. Kleven, Oddmund Fossøy, Frode Jacobsen, Frode Laskemoen, Terje Rudolfsen, Geir Robertson, Raleigh J. |
author_facet | Lifjeld, Jan T. Kleven, Oddmund Fossøy, Frode Jacobsen, Frode Laskemoen, Terje Rudolfsen, Geir Robertson, Raleigh J. |
author_sort | Lifjeld, Jan T. |
collection | PubMed |
description | ABSTRACT: In birds with extrapair mating, older males usually have higher fertilization success than younger males. Two hypotheses can potentially explain this pattern: 1) females prefer older, and often more ornamented males, or 2) older males invest more in reproduction and fertility than younger males. Here we studied factors associated with age-related male fertilization success in a population of barn swallows Hirundo rustica in Canada. We document that male fertilization success increased gradually up to a minimum age of four-year old. The age effect was especially strong for the number of extrapair offspring obtained and the occurrence of a second brood. The higher fertilization success of older males was also associated with an early start of breeding in spring. The length of the elongated outermost tail feathers, a postulated male ornament preferred by females, also increased with age (in both sexes), but it was not a significant predictor of male fertilization success within age classes. Male fertility traits, especially testis size, but also sperm motility and sperm velocity, increased significantly across age groups. Our results suggest that the higher fertilization success by older males is due to their higher reproductive investments and that their longer tails are an adaptation to early arrival on the breeding grounds. SIGNIFICANCE STATEMENT: The barn swallow is a socially monogamous passerine with extensive extrapair mating. We found that males become more successful in siring both withinpair and extrapair offspring as they become older. Their increased fertilization success was associated with a higher reproductive effort as indicated by larger testes, more motile sperm, and an earlier start of breeding in spring. The length of the outer tail feathers increased with age in both sexes, but long tails did not enhance male fertilization success among males of the same age. Long tails are probably an adaptation to rapid migration and earlier arrival on the breeding grounds. Our findings suggest that the commonly observed age-related increase in male fertilization success in passerine birds is better explained by life history theory than by sexual selection theory. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00265-022-03170-0. |
format | Online Article Text |
id | pubmed-9034975 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2022 |
publisher | Springer Berlin Heidelberg |
record_format | MEDLINE/PubMed |
spelling | pubmed-90349752022-05-07 When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? Lifjeld, Jan T. Kleven, Oddmund Fossøy, Frode Jacobsen, Frode Laskemoen, Terje Rudolfsen, Geir Robertson, Raleigh J. Behav Ecol Sociobiol Original Article ABSTRACT: In birds with extrapair mating, older males usually have higher fertilization success than younger males. Two hypotheses can potentially explain this pattern: 1) females prefer older, and often more ornamented males, or 2) older males invest more in reproduction and fertility than younger males. Here we studied factors associated with age-related male fertilization success in a population of barn swallows Hirundo rustica in Canada. We document that male fertilization success increased gradually up to a minimum age of four-year old. The age effect was especially strong for the number of extrapair offspring obtained and the occurrence of a second brood. The higher fertilization success of older males was also associated with an early start of breeding in spring. The length of the elongated outermost tail feathers, a postulated male ornament preferred by females, also increased with age (in both sexes), but it was not a significant predictor of male fertilization success within age classes. Male fertility traits, especially testis size, but also sperm motility and sperm velocity, increased significantly across age groups. Our results suggest that the higher fertilization success by older males is due to their higher reproductive investments and that their longer tails are an adaptation to early arrival on the breeding grounds. SIGNIFICANCE STATEMENT: The barn swallow is a socially monogamous passerine with extensive extrapair mating. We found that males become more successful in siring both withinpair and extrapair offspring as they become older. Their increased fertilization success was associated with a higher reproductive effort as indicated by larger testes, more motile sperm, and an earlier start of breeding in spring. The length of the outer tail feathers increased with age in both sexes, but long tails did not enhance male fertilization success among males of the same age. Long tails are probably an adaptation to rapid migration and earlier arrival on the breeding grounds. Our findings suggest that the commonly observed age-related increase in male fertilization success in passerine birds is better explained by life history theory than by sexual selection theory. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00265-022-03170-0. Springer Berlin Heidelberg 2022-04-23 2022 /pmc/articles/PMC9034975/ /pubmed/35535127 http://dx.doi.org/10.1007/s00265-022-03170-0 Text en © The Author(s) 2022 https://creativecommons.org/licenses/by/4.0/Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) . |
spellingShingle | Original Article Lifjeld, Jan T. Kleven, Oddmund Fossøy, Frode Jacobsen, Frode Laskemoen, Terje Rudolfsen, Geir Robertson, Raleigh J. When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? |
title | When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? |
title_full | When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? |
title_fullStr | When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? |
title_full_unstemmed | When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? |
title_short | When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? |
title_sort | when older males sire more offspring—increased attractiveness or higher fertility? |
topic | Original Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9034975/ https://www.ncbi.nlm.nih.gov/pubmed/35535127 http://dx.doi.org/10.1007/s00265-022-03170-0 |
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