Cargando…

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...

Descripción completa

Detalles Bibliográficos
Autores principales: Lifjeld, Jan T., Kleven, Oddmund, Fossøy, Frode, Jacobsen, Frode, Laskemoen, Terje, Rudolfsen, Geir, Robertson, Raleigh J.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Berlin Heidelberg 2022
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
_version_ 1784693218633318400
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
work_keys_str_mv AT lifjeldjant whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility
AT klevenoddmund whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility
AT fossøyfrode whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility
AT jacobsenfrode whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility
AT laskemoenterje whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility
AT rudolfsengeir whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility
AT robertsonraleighj whenoldermalessiremoreoffspringincreasedattractivenessorhigherfertility